CEP006 - Cellular Design Review with Roy Chen (Quectel)

one reason that we call it contextual electronics is because we're trying to give you a sense of how electronics work in the real world and i can't think of a more real world thing than a design review with a applications engineer if you don't know an applications engineer is someone who works for the company you're usually buying stuff from and they help you design that part into your product and so i've worked with a lot of these over the years but i never really had a good sense for what that interaction looked like because as a college student or as a high school student or really before you get into industry and before you have the the dollars of your company behind you you don't have a reason to interact with field applications engineers once you do if you are so lucky it's a wonderful resource really the field applications engineers they are experts in the parts that they cover and they give you feedback and ideas that you just wouldn't think about otherwise and so they are a wonderful resource if you can get access to them unfortunately as a hobbyist or as someone who's maybe outside of the industry you don't have them or even if you're in a different part of the industry you might not have them so i had the opportunity to talk to a field applications engineer from quicktel quicktel is the company that makes cellular modems they're out of base out of china they make cellular modems they're on the abc board that we designed as part of contextual electronics and i had a chance to talk with roy chen who's one of the applications engineers here in the states he's actually starting out in the states and north america because he's up in toronto and he's really great so this episode is me getting feedback on the abc design which is this cellular bluetooth board that we designed as part of the course and we i recorded it because when else do you get to see that i never could have recorded the interactions i had with uh field applications engineers when i was uh working for a company but you know this is this is my show this is my this is my life i get to record it and roy said it was okay and so i'm really glad that we got to so what this episode is is basically uh roy giving me feedback on this design i had followed the design guide that's from quicktile and so a lot of this is basically him kind of pointing out like hey you missed this part or hey you didn't do this part but that interaction is super important because having feedback and having a reaction to the thing that you designed that can save you time money embarrassment well it doesn't save me embarrassment because it's actually me it's roy telling me hey chris you didn't do this right but that's great that's what i am happy to show here so i hope you enjoy this episode with roy chen field applications engineer from quicktel and uh we'd love to hear what you think about it so here we go with roy [Music] all right so welcome to context electronics uh today we're talking to roy from quicktel and uh welcome roy thanks for joining me here this is the first time we've done this kind of design review on on camera like this i'm really excited yeah also my pressure is my first time too thanks for you for the invitation yeah well i'm really excited about using the bg95 eg91 all the parts that quicktale's making i think are really exciting uh and are really good fit for this project we're working on so we're going to be talking about it a little bit but you're going to tell us a little bit about your yourself to start with yes okay my pleasure to join the day i'm roy i'm toronto based uh actually i've been working with quite tale since 2010 this is my eleventh year in the quick retail wow yeah bef on the first two years at quicktale i was a hardware engineer so which means i have a very strong hardware background uh we can share a little bit later about the designs yeah and then nowadays um in charge of technical sales for northeast region uh including canada and the united states nice yeah i'm in chicago so that's why uh yeah it's a good fit yes yes good uh yeah i did we our team also did a little bit of review about your schematic and the pcb i think we can go dive we can dive into this part okay great great yeah first of all first tour the design is very impressive uh yeah just in terms because you you're considered to have a convenient uh compatible sorry you have a design for um several mojo in one piece b board like h91 pg96 p95 so we need to review this uh you can uh now i'm sharing the a pdf file it's called the design review report okay is it a different window maybe you can see or uh maybe i think you have to share that different screen so while you're doing that let's just take a quick look at the uh so i'll just for people that are watching that maybe haven't seen it before this is the the board this is the abc board that's been designed so while roy is pulling up that other pdf uh we can take a look at this so this is the yeah the multiple modules and uh the idea here is that on the back side we have uh basically the idea is that you it's a sandwich of you know some kind of daughter card and then the main module itself and those two things go together to to plug in to access the cellular capabilities and also the bluetooth capabilities of the nrf52 that's on board so yeah so these these are the uh the things that are you know this is what we've been doing as part of contextual electronics this is the the board we've been designing and uh yeah there's i'm excited to see this report so it looks like roy pulled it up here so here we go yep great okay let's go yeah normally we okay all right there we go yep here we go yes so actually you had a good design for the power just here you pay attention we recommend customer to anyone zero dire so this is like because the power for the module is between different module uh p96 e91 vc95 those three mojo have a little bit slightly different uh of the power supply range okay so pj6 because it supports 2g so the power ranges from 3.3 to 4.3 and if some customers they this they are going to use in the pg95 m2 which is a excluded 2g so the power range is between 2.8 to 4 4.6 circle more wide range and the typical yeah typical value vote for pgm63.8 so which is now that now you did a very good is 318 here yeah and that's actually a really good point too we i kind of stressed over that a little bit because the bq'd uh 25 895 which is the charger chip it has this kind of like kind of soft upper range so if you don't have a battery plugged in it's meant to obviously charge the battery but then it's this kind of range that can go anywhere from pretty much with the battery voltages so wherever the battery is in its life cycle if it gets if there's no battery there it kind of goes to the top of its range thinking like hey i'm trying to charge it might be at 4.4 instead of 4.3 like you're saying so it sounds like the zener there like you're saying would help to protect the chip in that in that scenario yeah okay that's great okay for the usb port you know for the um most of application using the pj6p95 they may use the usb port because you people is for eight command for uh gps and also for software debugging and for more updating yeah which is very important for the customer they if they don't have your usb port connecting with the mic processor we also recommend the customer to have this sport be reserved as a test point okay which you which like in the future when they do the certification at the verizon 18t they require to catch some test lock which uh usb port is the only source got it okay so that's that's a really good point too and i'd love to hear about certification a little bit more after we go over the review as the you know to to clue people into what we to that have not looked at the design before uh this is the so basically there's a second usb port the first usb port is for talking to this is for charging the battery the usbc is talking to the battery and also nrf52 enter 52 talks through a level translator to the bg95 bg96 eg91 but then i decided to put a second usb b micro on here uh to talk directly to that port in order to yeah like you said software debugging all that stuff and then also some people might just want to use the the ship by itself and that's also a possibility so yeah okay great great so in terms of the sim card uh ur port which is you had a good design and uh because you already put the volt shift so between the microprocessor and the uh module which is 1.8 uh yeah that was easy i just copy the app note i mean that's really a lot of my mo was just follow follow the app notes there's a really good design hardware design guide which i really appreciated from quicktel the um for for each of these parts so that was helpful okay for the rf parts i'll i'll go diving a little bit after this pdf and uh for sure just you need to pay attention for the 2g uh mode the current of motor will be reached 1.8 1.6 okay this is you know this gsm behavior yeah yeah those are really big spikes and basically it draws on the battery and also you need to make sure your traces are yeah okay and then you need to have a gps and the main antenna be matching the impedancy for 550 ohm which is like many customers they avoid or the ignore this and then when they produce pcp board maybe the thickness of this board is 1.6 or 1.0 so the trace layout the while the widen the sorry the layout should be different uh we can go we're going to a little bit about the rf design recommendation that'd be great yeah yeah for this for next one is adc uh because for pgn6 ever has two adc4 p95 has only one and this uh the voltage should never exist exit 1.8 so right here you did divide by yeah so that was just a generic you know voltage monitor divider there so at least the if nothing else if i'm going to keep that then i need to change the ratio i think i just did a one to one ratio so it would only get it to half half mark but it would be not as useful in that case yeah okay you can just put this as uh reserved and then just put the dmp okay next one used to boot uh usb boot is for emergency downloading purpose okay which normally this spins is open okay only one module like uh they run abnormal or mode and that it never got recovered so you have to move this thing to high for the downloading okay okay these those two bins if you're not using you can reserve the psm indicate indicator is output this is for mic processor they can detect if mortgages at the psn mode or not okay and what is psn mode uh yeah ps mode is power saving mode okay it's a week we also you can consider this as a deep sleeping mode okay okay yeah yeah yeah so right now it's yeah showing just on my schematic here the uh yeah so it's just dnp so you're saying that maybe hooking that over to a microcontroller would be prudent just in case i ever want to use it okay that's really good yes yes yes yeah the next one is the w disable this is a airplane mode to enable which is input for the module so you know when the module like uh it's just a very similar to ourselves when you have airplay mode when you turn up to not into the airplane mode you're not able to receive the sense and the message so this is like you can have this is one type of power saving mode but yeah just to disable the rf parts okay yeah so that's a good good thing to have there yeah okay and the the right side is ap ready this is input actually this is a input input pin from the microprocessor uh so with the more when the uh micros in the selected mode they can to uh like let the modern nodes like you this is actually being triggered you are the poor you know when the module when the microprocessor at the sleeping mode the module that the cpu is not able to process any data to receive any data and in one scenario is when the module receives message or the data incoming so the module can detect or wake up the microprocessor hey this is the message you should to receive and usually to process then they go to wake up then you are the poor okay okay so how and what would you say i mean like how critical is that i mean in terms of functionality is that more like a nice to have or is that like a yeah you should definitely like in all these cases are these all yeah you should always have this hook to the microcontroller is it more a uh if you want this function and it's specific to your needs then you should do it yes very few customers they may have very sensitive on the power consumption for both uh microprocessor and the whole system so they may have this pin to connect to the microprocessor because they want to put the mo the microsoft is always lower sleeping mode but also they have you have another alternative way to achieve the lower powers consumption like say you can cut off the power of mag of the module you can put the the power save mode and you know also like a sd micro xp micro they also very low energy um profile right which is which is which is good enough yeah and that's and that is that is kind of the thinking there that to have a kind of supervisory micro in this case the nrf 52 is pretty low as well being able to just kind of go into steep sleep and then shut the cellular all the way down um yeah so it is using it more like a modem as well uh i should state for people that haven't seen these parts before there's a full arm core there's a full arm uh processor inside there that you could use as an applications processor for a lot of these right yeah yeah great uh this is about a schematic and then we can i have i have another point i want to show that's when i okay you can see my screen yep oh this is the slideshow right that's what you're seeing this slide yes do i need to full screen let me see uh that might be helpful yeah i think i think this is the presentation view so that's why it's it's not full screen okay i think it's okay yes that's okay there oh this is okay yeah that's great but now it's better huh oh yeah that's great yep yep so uh also part of schematic uh for the antenna design so for the main antenna which you already reserve the pi matching which is good yeah and because this is uh normally for the testing and to match antenna sometimes when they have a second hole or hormone interference so they will have adding some capacitor inductor to reduce it for the gns antenna so i i realized that you have this antenna it's only for passive antenna i don't know for your application do you need a pass active antenna in the future or no oh that's a good question yeah um you know it was more of a placeholder honestly at the beginning i'm not planning on using it um but that's i mean in terms of a placeholder that is a great time to think about it so you're saying to maybe put in a spot for an amplifier or something like that there actually morgan has a rna lower noise amplifier already built in so you what do you need when you have the power for the for the power for the antenna which is my level my right side is vdd 3.3 volt and then you have a little bit large 10 ohm 10 ohm resistor and then larger inductor switch is enough okay and then that so then how how does that actually look on the physical side so like if the antenna does the antenna have is it not like a ufl or something like that it's some or is it just coupled in to the actual coaxial connection there which is that rather it's not any uh impact just to hear this for the power only okay and um just to you have a little bit increase the size of your pcb port because the resistor we recommend is zero eight zero five okay and the inductor can be zero six zero three and there's another one capacitor which for the power filter yeah yeah so it is it is pretty tight up up in that area so yeah that is maybe the reason not to but i think that either way that's something to consider and something to look at so that's that's great yeah okay yeah next one uh for some for the customer they they do not have usb port but they are using the gps application and we offer one option by software we have the you know when using gps you need to have a nema sentence nema which is a it's better to have the full sentence output like every second you refresh in the sentence location and if you don't have the usb port which you're not able to get from the ape from the main port the main port only reports one sentence by week by inquiry okay and so there's a polling versus a reporting kind of idea yes yes okay and then uh we have the another option is uh ur3 the third ur port is able to have the output like same feature as a usb port if you don't have usb port so this is like option for for you for your next line for or maybe when you need a gps functionality okay that's great to know yeah so right now the usb the sim uh sorry the uh the modems uart3 i believe goes up to the daughter card um so i would think that if we need to use that maybe we could use that as a reporting and just tie it up through the daughter card back down yeah you know yes yes okay great but don't need to worry because uh also without your ur report you can also able to get the gps location or acquisition from the you have to pull it and you say hey what is your update what is your correct yes yes okay that's great our next one we can jump to the pcb sure sure and i'm going to pull i'm going to pull mine up on my screen as well in case there yeah so i i had only sent so so as so people know um i had sent roy uh the pdf of the gerbers basically or pdf output uh so we'll actually have access to the the 3d view here if you want to take a look at that so yeah okay go ahead though yeah yeah in terms of the footprint of the three module i really um yeah i noticed that you have um this module is like maybe you have referring to the p 26 yeah probably which pizza six is like a middle size can compatible with uh p95 that's the only one thing we need to pay pay attention because when you do the h91 another one is keto one module then the size the outer line is a little large then b and six oh interesting okay so yeah so same footprint but the actual physical outline you're saying yes correct okay interesting so which you can refer in to the the one here in the in the top yeah so you have our line for a different module so you can and also on the module physical on the module on each each 991 motor the the four corner has a four ground pins okay yeah we should uh yeah yeah yeah okay and so like looking at the 3d model here too so that that might be one of the biggest uh so right now i so so i talked to quicktale about the basically i have bg95 in-house right now that's what's gonna go with my prototype um but yeah you could see that it is pretty tight there so uh especially i would say the biggest concern are i'm not sure what the the gap difference is but like but this right here i really squeeze that in so yeah yeah that one's gonna be the biggest one so that's good that's good to know um so i think initial testing i'll probably leave it but then yeah any kind of revisions i'm gonna have to probably move stuff around if i want to get access to the to the cat one capabilities yes yes okay okay uh in okay for the next page i'm showing the uh the difference between the pgn and sp995 mm-hmm yeah so there is two main pin uh two pin difference between two module is one adc pin which is you already designed like for that as a test point and another is the resulting which is a critical for the for the module for the for both and then adc pin on p96 there's two individual adc one adc two but for p95 there's only one and then and also because actually uh p95 inside of those two bins connecting the same one pin for the to the chipset okay so that's it so it's labeled differently externally but then with the thing that's actually where the resource is actually going to internally on the silicon yes this is the same rather yes and also the same thing for the recessive and the power keeping for p905 so which we don't recommend uh the power key should never put down to the gender permanently this is very important like you should never be pulled so like the pull like if you're going to just tie it low always you mean correct yeah you cannot do this because you know several customers they they are they just tried because some sometimes you have lack of glp from microprocessor you don't have those pin to control the mario and say yeah let's just put down because once that just goes all the time right and we'll try another software or something yeah yes yes yes yeah because for the most in the in the past but almost for them all of the kettle one card for 3g 2g mojo it's the same uh architecture architecture so which put down the motor will be or make it turn on perfectly in this case p95 is not that applied to so you have to to control power key and then to pull it down and then put it back yeah yep yeah it is that it's that pulse that that is in the hardware design guide and and it's inverted as well it's um there's like a just an npn inverter that drives yes yes and also inside the chipset inside the bay i mean the i mean basement of of the the qualcomm chipset and there we um we uh distinguish those two the pin the functionality by software like if you press longer of this pin the mojo is going to reboot oh really okay so it's like a ad hoc reset button yeah yeah correct correct yes oh so right here it would really not work well then if you tied it to ground huh yeah yeah yes so it's called do we put always yeah so it would be it would be a bad that'd be a bad startup time yeah yeah yeah so only this is you need to pay attention and a big difference between two modules and the next one uh here's the one another pin uh called the p-o-n trigger this means only for ps95 we added distance to wake up from the motor from wake up the module from psn mode okay yeah normally you have the way because like i i also need uh uh i like to introduce a little bit about what what much during during the psa mode okay sure so during the ps mode modules power supply is below 10 micro amp is very low it's like almost turned off and then during this mode the motors or every part is sleeping only the fresh memories is keeping this information on their network registration name and it's not able to like receive data or calls or anything like that it's not in receive mode correct yeah yeah yeah totally correct yes and then you you when you need to wake up mojo you have to operate as the first time to power on the module to power key and then you have the power key to turn on on the module and then for the v95 besides the power key you have another option this is a power on trigger to wake up the module like this is the additional pin for the p96 p9005 sorry yeah okay so this is another one where i should be so is this the the kind of case where i should be doing uh like like the power key i should have like an inverter and driving that i think one of the problems is that i was starting from a bg96 footprint on board yeah um and then but then there are some pin differences so that's that's on me for not uh having the pin differences labeled here on the bg95 yeah on your card design which is good and you can also use the power key to pop to trigger the module from the from wake up from the ps4 mode so you can you put it into psn mode from software and then wake it up with hardware using power key yes you can sure okay so wake the idea is that the feature difference is that you could also have a little bit more hardware control using this pin that you're talking about yes the wake up from ps mode f2 option one either the timer you know actually ps modes control the timer is controlled by network and then they'll be wake up when the timer runs out and also the hardware like for example you need to have a wake up module to do something manually so you wake up from the by the hardware which these two options all it's always available okay that's great yeah it's good it's good there's a lot of options it's yeah it's just kind of making sure i think the one thing that uh so i had uh my firmware engineer uh eric uh who's a friend uh on on a different video i'd done and uh and one thing he always talks about he's like make sure there's at least one way that you can always have an escape mode and like get things working and and i would think that you know like having at least one way to reset the the chip and getting into the right mode is really important yeah okay okay great yeah next one this is like a little bit design tips for the sim card uh actually personally i had a very good experience once i was supporting one of customer they made a design for the sim card they also 100 following our design guide so edit the capacitor and also edit the esd but they didn't pay attention about the esd the components which here we are mentioning the peristic capacitance should not more than 15 fifa so this is very important because you know the sim card have two kind of uh voltage either 1.8 or 3.0 nowadays volts is 1.8 okay and then you know here you have a capacitor you have the usd we need to design an imperial capacitance is going to increase right and then they're going to delay is there a number like a total number of the total capacitance value that should be on there between the the diode and the and the so here yeah we we put here is a 30 33 plus 15 plus 15 which is uh no more than 45 yes got it okay great so uh otherwise you the data like a clock data is going to delay it yeah right it's going to be rounded edges and you know delays times yeah because it expects basically it's like a it's almost like a serial protocol where it's sending out basically the modem is talking to it and then it's expecting some response within a certain amount of window right yeah yeah yeah yeah this is very critical yeah cool uh this was this part it's about art design uh we can this also we have we provide our layout application nodes oh great yeah i'm going to open this one okay great and let me i'll pull up while we're doing while you're pulling that up i'll uh i'll show the layout where we are here um so based on the stack up so we're using jlc the 2313 process um and so looking at the back side here basically what i calculated using my tools were um uh was using uh what is this let's see our design rules here so the design rules for rf point two millimeter point point two millimeter uh space point two millimeter trace and that was going to get us i think it was like 50.3 ohms based on based on a coplanar waveguide design so that's that's where my numbers had come from as as a starting as a starting point i'm sure i could have been wrong so okay we can't we can uh reviewed from the page sure okay can you zoom in a little bit on that please can you see no yeah better it's great yep yep so here is uh we noticed here the power you are designed for the to the module and we recommend that the power the voltage though why them should not no less than two millimeter okay yeah and if for some customers they need a longer and also but also very very important because you have you you're doing the four layer for this design which is this is that you can just yeah which is good enough and so just to be clear that is i think that's on the i'm just looking at the design here as well i'm just trying to so there's two power areas is that do you know if that's the rf rf and the base band yes yeah so but is the is that the rf or the baseband input that you're talking about there oh yes this is uh this is baseband yes this is baseband huh so i thought that's here the lower left corner is that right of the of the model this is uh this is a top i believe this part you're you're screwing this third part is it's okay okay all right so then you're talking about um sorry the r uh okay the r rf section up here you're talking about i make this a little bit easier for people to see too so i'll turn on high contrast mode and so just for clarity the this is the outside of the module here if we look at the uh i guess i don't have the backside silk turned on there's the edge of the module so this is the top right corner oh this is flipped view sorry i'll flip this i put the module on the back side so it's a little confusing uh okay so then yeah so then that's why that looked a little different here so you're talking about this section here yeah the the trace you're saying the trace going to the 3.8 volt rail should be two millimeters minimum two millimeter at least okay great that's good to know so then basically i could change that in the uh in my design rules to say so this right now is oh wow how would you even get two millimeters would it just be a ground pour or what i guess you get ground pour pretty easily so those two pieces should connect uh directly like uh right yes you're saying like just have you mean the two pins connecting directly into the ground yeah yes yes okay to the power of the power of power right okay yep okay great yeah i'll definitely make that change okay so next one is about the use sim card uh we noticed this let me see uh here the power for sim card vdd and ground more than 20 mil or maybe here just maybe this is a 12 or some 16. okay this just yeah yeah i think i know what you mean so that's uh to show mine here so that's uh so the sim card reader is on the front side and this is the back the backwards from all that so you're saying that the the power going to that pin uh specifically so that and it is kind of interesting that the the um the ground and power are both sent from the module itself so there's grounded yusem ground and using power that are both sent directly to the sim card instead of just giving it like a like the 3v3 or 3v8 from the rest of the board yes yeah because the reason we recommend this way this uh the the design on this way because we had uh experience on our module in the past uh several customers the tcp board is more complicated than yours and they have a digital ground they have another ground maybe i have another ground yeah so once one customer they connect the ground to the energy background which is uh it's not imagine let go though so it's always like the sim card is initializing the fail so which means now uh if even the pin inside the module is connecting directly to the uh the main ground but we recognize it using the sim card got it yeah that makes sense yeah i mean yeah and just to have a known flow and then for troubleshooting as an applications engineer i'm sure you can be like well you didn't do this thing and so that's a good place to start as a troubleshooting method okay so that's good to know yeah you're right this is like a it's a very that's 3.5 mil trace that's way too small so yeah how much power does a sim card usually take oh it's very small maybe just a few m amps okay all right so just a as a general design rule you're saying move it up to a larger trace just to make it easier make sure yeah okay great okay next one i want to save here so here is a little bit the layout discussion for the ur for the sim card circuit and then you have the from the more japanese and then you have you have siri zero ohm and then two power 33 capacitor and then est and then connector yeah okay so this is like this we recommend this sequence oh you're saying the order of the order yeah from the mo that the trace so some of this might have gotten shuffled as i was moving between different and i didn't put the board view back here just so people are clear but uh you're saying so we're kind of looking at the same areas here now of uh so you're saying that because so what was what was the order again uh from the morgue you are looking from from mojo code first to the zero ohm okay and then capacitor i see okay so the yeah so it's the yeah it's same as the york um is like four in the sequence of the schematic yeah so for the reset line here so sim using reset goes to resistor yeah resistor to the capacitor capacitor got it and that would be c42 and highlight that here so c42 and then finally go to the connector so yeah it looks like and then you also you need to pass the esd and then to the connector yeah so it looks like this yeah so this is the esd and then then which is the one to go to the connector so then this one i see because of yeah so how how that's all hooking together so this is finally getting to the connector down here so it's it's kind of hopping around a bit so okay and what is the reasoning before that uh that ordering just just as uh in case you need to put like resistance in line later instead of the zero ohm uh you know because in some cases you know it works you design like according to the mechanical some sometimes you have a large or longer trace which you need to go from merger to the sim card so we have to say this way you have to keep each pin as a very similar distance similar uh length and then you have like a similar design architecture yeah that makes sense yeah okay that's great and then we also mentioned here the v the main main power trace should be away from the sim card signal okay uh yeah yeah and and why that's just in case there's any like noise that couples between correct yes just about noise or the power drip power drop something yeah how sensitive how sensitive are sim cards uh it's like i've actually forget m1 i think it's very less because sometimes for 2g for kettlebell kind of four you're sending the large data the mojo is power consuming large compound consumption which uh causes the massive interference which that part maybe is more impacts but for this kind of one i think uh this is that to say just to say as long as you have the space you're able to make this happen so keep it as far as possible yeah that makes sense yeah and i think that the um yeah like in a 2g if you have these huge huge swings of current you're also going to have the equivalent inductance that happens and coupling to different things so emi that happens so yeah that makes a lot of sense okay okay cool so here is the part for the usb so we recommend you have this the like this is in differential pairs and then between those usb ports should be surrounded by the ground i know if you if possible okay yeah that's a good point so let me pull that up on here so that's something that's coming in on the back side um of this design and so these to change a little bit i got some feedback from the uh the pcb house that my space drill holes was a little bit low so you're saying though like so then it comes in here so this has ground all around it but then on the front side uh now this is isolated here yeah yeah yeah that makes sense okay so that would be that's actually not too bad because then i could just literally drop a if i can find space for a a uh a ground uh plug here then i can i can fill all that in so that's that's really good to know yeah so i'll definitely work on that good yeah actually i could probably even do that here there we go i think i got it yeah almost yeah okay great good yeah for the next one is about our parts um oh here i think you consider about the mechanical or the like influence between this screw hole you have this layout it's a little like a curvy and i don't know if possible you have to put this a little bit of weight up because and then you keep the trace arbitrage away from the power yeah so you're thinking maybe have it um so yes to show people let's say maybe you can reorganize the the capacitor or the resistor of the arf then go straight from a level side not too tough so pin 49 you're saying to go from pin 49 up to to the uh this is the ufl connector oh okay yeah yeah and so i think the main problem is just that the module edge is right here oh yeah yeah to get an actual pi filter in there was was very difficult now i guess one thing we could do is i could do more of a straight shot and then you know remove the pi filter but then that has its own risks of you know there's it's likely that you wouldn't be able to yeah yeah actually on your design because this trace is very short and i'm in total maybe less than one mean one centimeter or 10 millimeter which is uh should be issued enough so we have a much kind of very less little size slightly uh cable loss and also you did a very good design on the ground pins ground vias and i'm going to show you another pdf okay that's great yeah that's one thing that um it was hard to kind of get in in here it was tough to get the the vias and definitely like i i was thinking about it being right over top the power and that's that's just a function of like the fact that there's yeah there's not much room to get other stuff in here so i did have i guess this is a capacitor here and this is um this is just kind of the range of different parts so i guess i could remove some of these i i basically i had i had a bunch of like really large i guess on the the top side i have really large bulk capacitors here i turned the modules off healer but uh i had i had all these these caps but nothing could fit up here where the rf powered and that was really the problem for a lot of this is just that there was not room for the power even on the back side i see i still like right that would have been up in here so and also the height restriction so i have a height restriction of 1.5 millimeters so what i tried to do is have um i i switched from that 12 10 or whatever that larger package was i think maybe in 2512 down to o603 but i have a bunch of them in parallel because i've experienced in the past of having um brownouts due to you know during transmit and thinking about cat 1 being a little bit more stringent than a cat m1 that's why i wanted to have a you know a bunch of parallel capacitors there okay good all right so you said you're going to show another pdf here yeah um yes here so this is the generic arf design recommendation uh which this part for the schematic we have pi mentioned recommended which is same as your design and then uh here this is called um clamp clamper design so here we did as a simulation about the uh the hive i think it's a pvp board it's 1.8 sorry 1.6 and then what's the trade chase what's the why then what's the clean reason we should to design that's an interesting uh difference too because um so the the stack up that i'm using is actually it's only 0.1 millimeters versus 1.6 millimeters and so like you talk about the difference in trace sizes is like is significant and so that's why i think i think if you do a two-layer design and you have that thicker trace uh sorry the thicker board thickness um you can make a much thicker trace which also fits that coplanar waveguide better but in this case i actually ended up if you look at the the design here um the uh i ended up necking all these down because i had to use this thinner trace in order to hit 50 ohms yeah these are these are like some some things to neck the back you know to to go back from a thin trace to a thicker pad normally i would try and get uh a uh you know a thicker trace that matches the size of the o402 components but in this case uh since i'm using a low-cost board house i i can't define the stack up myself so i think the answer normally would be you know define your own stack up do your own thing but i know yeah yeah yeah cheapskate so that makes sense yeah sure yeah here just to say pay attention on the design like we recommend here like as you did you have several years ground vias between those garfk arf cable this is to create a rule for the ground signal to benefit the back right yeah yeah this is important yeah yeah i've had a lot of trouble with those sma connectors that you show in that drawing there actually not because of the the sma connectors were fine the trace was you know the correct width and everything like that it was actually because right when the tr the thinner trace hits that really big uh mount point so like yeah that's actually been my problem in the past where you have this huge discontinuity because it's like the trace is happy it's happy it's happy and sees this huge bulk of copper and it's like i don't know what the impedance is anymore and then you know you know especially like when you're doing gigahertz level designs it really starts to matter like in the megahertz it's usually you know 100 megahertz it's okay but the higher frequency stuff can really start i'm not sure what bands are up in there but it can really start to mess with your mess with your signal integrity yeah i agree i agree yeah so this is just a general for the arp design i think right here back here yeah that's all about the your schematic and the pcb layout review and then for the customer who needs more information we have here uh the download link so for three more years great yeah that's really great so what about so you mentioned the um you know some of the certification stuff so talking sending off to verizon at t things like that what does that process usually look like for people that are interested in that and that sort of thing yeah first of all the board is the verizon entity pdcrpfcc approved and then we uh we do the certification for verizon now rather you know during the pandemic so they changed the way how they set a certified device and module okay uh used to they put a very difficulty for the module and the both mojo and the device and in the past you have to be sitting in the lab in the lab and then during the like week two weeks for them for the device certification nowadays they simplify the process for the device but they're more complicated make it complicated for the module right the sucks for quicktile is great for that right [Music] more in-depth look at the the transmission characteristics of the of the rf front end or how does that how does that end up impacting things so for the various tanks take example for you for the verification so now they have like few cases it's more network ready related and the one just one of them is very um like a mandatory case it's called a data file or of the air upgrade so with the default a folder firmware and this part and then for the old customer you once you have the account on the caller open development protocol um and then you have account you have you're able to submit your device information to tell them which module you're using and then you you download the test case okay and you can do the test in your office and then submit it yeah and you can submit over test log in then because also everything has to be linked to the browser server they also they can monitor the test the process and what's that well what did what did you do what form were you using like and this okay that's great so that's actually really critical too that's why you said earlier in this recording that you need to have that usb connection so that you can log the data get the firmware if you need a different firmware set in there to make sure you're passing all these tests yes and then we have uh in the criteria we have uh one expert uh who in charge of the certification and then we can introduce you to by email his name's young uh he's um have been in this industrial for about 15 years knows all the key people in the verizon agency t-mobile and in crypto we have certified about 50 more than 50 device in north america last year and it's great yeah and uh i mean like different skills different uh variants like this from keto one to from kingdom one nerve now t uh kettle one kid four six and also can 18 now we also working on 5g as well oh wow that's great yeah yeah and um i think i mentioned the the road map i think i may have looked at it on the video a little bit but um i really like the idea of these like mostly pin compatible you know like there are some differences as we talk through but like i really like that idea of like being able to just kind of swap out the module that's on there so i really hope that quick tell keeps doing that i think that's that's a great like upgrade path for for future future modules and you know instead of redesigning the whole product on my side it's really just buy a different part solder it down and then it becomes this different technology that really is helpful and that already could exist for different regions and different you know capabilities and stuff like that but i i really appreciate that in the module makers i think that's a lot of the value yeah we have several options can be comparable from kettlebell to you can do from 2g to cad m1 or k01 and yours isn't even careful and also look at four two keralanka and then different different a little large and also in the future we have a m.2 mini visa ie up to two is kind up to 5g so which is also it's compatible yeah that's great that's great yeah and uh i i describe the you know the cat one cat four cat on one stuff like that but could you give a quick rundown for people that don't know what that is that might be watching this yeah sure yeah like our cell phone we can consider first ourselves kind of about kind of four you're doing that you can do in the videos streaming you do the video call so which the cad four is the upper link is 50 meg down in the 100 mag pbs so and for the application for the video streaming so metaphor is suitable and for the customer they're doing the like tiny data and maybe something picture that's the maximum like when you have two meg or some file the kettlebell is enough and also kettle one card for the coverage it's in it's already there for a long time yeah forever right yeah and that's actually a reason that i i explained um when i was starting this stuff as well like that i was interested in the swap is that cat m1 even though it is out and is broadly available it's not available everywhere and being able to switch to cat one in certain places in certain you might be able to look at your phone and say hey i've got signal and then cad m1 your little device doesn't doesn't work yet and you know it's on the way but it might not be there yet actually yeah it does because kettle kettle wine has already been announced and then deployed since about two years ago now the coverage in north america and canada including us and canada is quite a very natural already so based on our customer because we all been shipped about more than five million maybe eight million already for kingdom one in the north america which uh the feedback is very good very positive about the coverage good and then uh that's also for kingdom one the penetration is networking which is better than keto one because the consistency is the minus 100 minus 110 like this and then for the most communication like we call the lt m2m the people doesn't need to lower higher data rate sending an only piece of their information once a day once a week and then kettlebell lines will be a very good option for like a metering application uh lighting we have a customer like doing the lighting stream lighting lighting like industrial lighting okay not like uh your light bulb's not cellular connected but it's someone's like light ballast in a gymnasium or like a factory might be might be yeah yeah they call this smart city oh sure yeah and i guess yeah light uh like uh street lights right that makes industrialized and then because you know wi-fi in the in the middle of the the road yeah the reason of this market is booming because you know the cost of kind of wine is getting down and low and lower and then they are able to replace the gateway yeah which is used to roll the erosion one two six or maybe one to ten one to one hundred of gateway in between the each you know they're communicating with the short range or zigbee and now with the kind of one the classes can be they can able to install the for all the units so that i also and the camera one for my version personal understanding like you know 2g is there for the some country they have if they keep in 2g they may not to implement the kind of one because 2g can win also supporting the mobility that you come to the movement for the tracker this can do with the quinoa right and yeah you see that a lot with like the sim 800 sim 900 like the small modules a lot of the maker boards that are out there use those still and they are active a lot of places but uh some of you at least in the us a lot of that is getting shut down and getting you know the band which are the uh the uh the white space is getting moved around and allocated to different things yeah for the for some kind for the country like us they shut down 2g for some i mean maybe they are the first country shot to shut down 2g so that reason they more preferred to have kingdom one network coverage yeah and then uh t-mobile the first uh carrier improvement navy actually there was for the lighting and project in las vegas it's first city programming and also europe for the country they keep 2g they may they they prefer to have a nationality because i'd like to say uh can never lts come to kind of electric knowledge to replace uh short range like 0b bluetooth by um uh like a 900 mega 433 mega so those kind of then a chick chip can be replaced by never noticed because the cost is similar and also um for the executive or roller this kind of you need to have a central network to be viewed yeah yeah so one of the one of the thoughts for this sandwich you know this module that i'm thinking about making is you know maybe throw a lora module on there as well to extend it capabilities but like you're saying it would some you need to have some kind of node that basically acts as the as the capture for all the the smaller nodes and then maybe bundles it up puts it into a network packet and sends it over to the server so there is yeah you have to have the central like a network that to create a center yeah an individual sound spoke instead of directly back so yes by using cellular which is simple just to program the play this is the most advantage in the beauty for the cellular module that's great yeah yeah i mean yeah being able to get a signal anywhere well almost anywhere you know deep deep wilderness you got to go to a satellite i think but uh yeah any city uh it's especially like all like you said asset tracking like being able to track where your your food order is throughout the city it's like you know that that doesn't come for free that someone's got a cell modem on their on their device on their bike or you know their caviar bike or whatever so yeah uh here in my screen i was sharing the latest this data is after june first okay this is about mapping network development worldwide you can see that the purple colors cover both northwestern canada and the south and south africa south america and also mexico is using att network so it's a kinemon plus nerve and iot and the europe is kind of mixed so it's kind of one airbnb and china we also going to have uh kermawan both both and australia is the pure uh catamount yeah this yeah that's another thing that's interesting as well because like even though these these are the technologies the cat m1 and nbiot are like the two different types of technologies those are the frequencies that they use all that stuff but then there's also frequencies within those bands as well that are i don't know do those crossover more than than some of the the gsm stuff used to because i know that there's different modules types that you need to get in north america versus worldwide and those kind of things oh yeah they have uh they have several mainstream bands they're using for like for north america they've been 12 13 and 5 is the main it's the main band which is a all of them it's a low band it's about a 700 meg and then for also they are i'm doing like a banner 66 then 71 it's also about the 750 yeah it's below the function of the gsm and which it requires a longer like a longer large size or antenna design which is also important for the customer who wants to achieve the tiny size of the product they have to concern about their antenna size as well right yeah it's always that weird trade-off of like yeah you need the bigger antenna but also then you can get through walls a little bit better you know like so it's like that weird you know it's like it's a tiny little silicon device with the huge antenna hanging off of it yeah by design there's a tiny size you already sacrificed the performance of antenna yeah and also the the good thing is att they renewed to test the standard for the canon one tiny size they have a two different deck category big size you have to achieve the 20 db or 18 db uh output you could um trs trp but for the tiny size like they put the dimension less than 20 uh about 20 uh millimeter something like this centimeter like this so that was only needed 12 dbm dbm outputs which is very good for the right it's easy to achieve it's easy to achieve oh that's good yeah yeah there's a lot of really interesting things and i really appreciate the fact that you you know came here to record with me and you know give me feedback on the design that's really valuable yeah roy where could people so people are interested in building their own designs where can people find information about you or using quicktile parts or you know getting design reviews and things like that yeah okay uh i have my email right here so and it's at the very beginning so this is my email okay and also we have you know our website we have the inform information inform at quicktale.com so we have sales north america sales at the critical.com so we are easy to approach and we have um more than 10 engineer engineers in uh based on local based we can support you in exploring in real time and um yeah we have a very strong team here every day awesome yeah well roy thanks so much for joining me i really appreciate it and uh i i'm looking forward to implementing the feedback you gave and uh and uh getting some more getting these boards back and trying them out so thanks thank you yeah my brush too yeah it's my first time but it's impressive and it's very very exciting all right thank you thanks so that was episode 6 of contextual electronics podcast uh a little bit different than the other ones you know it was more roy helping me and i realized that's a little different it was less pointed questions about roy's background and usually we try and get more of a feel for for uh what the guest is doing but roy was such a great sport to play along and i really appreciate him giving me that feedback and giving me the advice uh if you want to reach roy we'll try and put the contact info in the show notes if you are listening to this and you want to see some of the diagrams and the things that uh that came up in this episode those will also be linked in the show notes uh of course if you want to you can always go and sign up as part of contextual electronics the contextual electronics people have seen this entire design process and they actually have seen me make these some of these mistakes in real time or oversight so let's call them maybe not mistakes and uh that's kind of the thing that we try and do with contextual electronics we don't just try and show all of the stuff like we are here uh we try and show the entire design process and that's kind of the idea of the course that you're seeing as i'm doing as i'm making these decisions as i'm doing part placement part choice all of these things and then eventually you know coding and we're into the build and the coding and the troubleshooting all of these different steps we're trying to bring forward all of the things about electronics that might not be obvious from the from the outside and and this is from my perspective as well right so as someone who started from no knowledge at all to moving to where i am now 15 years in i'm trying to bring the things that were super confusing to me to the forefront and so hopefully that's 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Channel: Contextual Electronics

Views: 1,349

Keywords: Quectel, FAE, Cellular, Design, Modem, BG95, EG91, Design Review

Id: AtNINEi8YAA

Length: 62min 54sec (3774 seconds)

Published: Tue Sep 29 2020