 They're great search brought to you by Did you key need a fruit lady to what is a great search this week? Okay this week? We're looking at quad microphone ADC's so You know oftentimes folks when they're doing an audio interface you have stereo left right You know microphone in left microphone in right line in or maybe speaker left and right It's not that usual that people have multiple audio inputs However, this echo dot tear down has four microphones because you need four microphones to do voice location and Onboard is this chip the ADC 514 0 it says ti on it So I know it's a ti chip and I thought let's take a look at it And then maybe even make a breakout for this nifty chip because if it's in the echo dot it's probably a pretty chip so Going to dig a key You can just search for ADC 514 0 and There's an eval board and it's like 300 bucks stick 250 bucks I'm sure it's a great eval board and it has like this XMOS chip Which if you remember from I and MPI we talked about this XMOS chip It takes the ITS data and actually does a lot of the algorithm work for you To like how automatically give you they have like a you know a ready-to-go program that takes This quad Microphone data and give you gives you the location data I think here's like the microphones are on the square here somewhere Anyways, so let's check out the chip itself So I2s Codex Even though I wouldn't necessarily call them ADC's and DAX. I mean yes, they are but they're kind of like not Normal ADC and DAX because they use I2s They're still under this special purpose ADC DAC data equit like I wouldn't normally call them data acquisition But like technically they are just be aware that this is where I2s codex live not a big deal. Just so you know and If we look up this Data sheet this is in fact a quad channel 768 kilohertz Burr Brown audio ADC so the Burr Browns are they're really nice quality If you look into this in more detail, there's actually three chips in this family that TLV 320 ADC X 140 and each one of them has slightly different Power supply sorry power supply rejection or I think dynamic range Try to remember but like the they all have slightly different qualities and you're gonna pay more for the slightly higher quality versions This chip is really neat because it's kind of strange to the point and I like that You have four inputs. You can have analog or PDM digital inputs. I like that. You have a lot of choices There's some power it has a Microphone bias output really handy if you're doing electric mics To keep it nice and quiet. It has analog digital control. It has a 1.8 volt regulator built in So you give it 3.3 volts and then you don't have to worry about giving it to power supplies It'll it'll handle the 1.8 for you You can communicate with it over I squared C or SPI That's where it seems to be a little bit more likely, you know, like I've seen more chips that are I2S Codex be controlled over I2C, but you know, you never know. It's good to have SPI there And here's the thing I really like about this Besides the shutdown pin just very handy for when you want to you know, you you keep it low So you don't have any noise come in which is for speakers you want to be muted But you notice you don't need an M clock pin. You have F sync B clock and data out And so you don't need an M clock pin, which makes it really good for use with a Raspberry Pi computer There are some chips that don't have an M clock or like driving the M clock for I2S is like it's unavailable It's hard to use or something especially the Raspberry Pi It's one of like the most popular boards that I use that does not have a master clock pin So not needing it because it has a PLL built-in is quite nice. So look for that if you don't see M clock, you're good It does this data sheet is quite long so like, you know, I was looking at this and I was making a breakout and It kind of it goes on like there's there's a lot There's like a lot of filters and settings and like you kind of see this is like I'm getting into like page 60 and like 100 and I was like, well, you know, I'm getting a little terrified To get this up and running, you know, it There there is a Linux driver that's out of tree that I could use but I was like, oh man There's just so much configuration to do Like look at like this mixer. Oh goodness. So I was like, well, maybe there's something although I really liked how simple the schematic was I love this the simplicity. So it's like, you know what? Let me look for some other quad ADC chips and see what I can find. So Here's, uh, you know my quick tip. I Can always get these I did design a board for this in case But let's go for an ADC. So DAC would be a speaker driver ADC is a microphone driver active I Don't really care for the I2C or SPI. So I'm gonna leave it unchecked. I do want it surface mount Of course, and I want it to be four channel quad channel So I click that and I don't need it to be part of this family. I was like, well, what other Quad microphone drivers are available This was kind of handy so view similar So oh by the way to you wondering like well, how does this even work? Like you have four channels of audio on a stereo I2S connection uses time division multiplex multiplexing TDM so that for each channel it sends, you know multiple chunks of of data so you like you have your driver has to know to read, you know 64 bits of data on each channel and then you get the 32 bits out or 16 bits on each 32 bits on each channel Cut it in half and you get 16 bits for each microphone, you know two on the left two on the right basically but whatever Okay, so let's look at what we've got so What I thought was interesting is this I don't know how this is sorted, but there was this chip Right here the PCM 1840 and it's also a quad truth even says quad channel 32 bit 192 kilohertz audio and it was even the same package Which I thought was neat and it's I2S pdm I2S TDM But notice it didn't doesn't say I squared C or SPI just thought was interesting So when I went to this board and I opened up the data sheet The data sheet for this if you look at the simplified block diagram and you look at this this chips simplified diagram hold on Gonna get there Is you'll notice that it's like well, they just totally used like the same graphics But what really is going on is this almost exactly the same chip now there's a couple differences in it, you know with with a pinout because The PCM 1840 it's interesting is that it's it's almost pin-compatible but it doesn't have an I2C interface for configuration instead it uses only bootstrapping pins, so FMT zero format zero and MD, which I think was mode zero there's these one two three four five These five pins and that's how you configure the output So you you can set some different filters and you can set up How you want the TDM I2S out to come out and you can only use I2 so you can only use analog microphones You can't use pdm, but It's a lot simpler to use data sheets only 40 pages long They show you here's you know the couple there's a couple different settings Look you can only do four things with it. You can Have it be you know for channel output TDM to channel to channel you can either have it be Slave mode which means something clocks it to get data out or the other way around where it pushes data out on its own clock And I kind of liked that this was a just hardware bootstrapped chip I thought this was a very interesting chip, so I'm glad that You know when I looked at one chip that I thought was interesting Take a look around see what other chips are in that family even if this one has a totally different part name But it turns out that this will work much better for me It's less expensive. There's tons of them in stock. There's like 12,000 in stock or something ridiculous. What's the price and this is about? 225 in quantity But it's got that reliability of it a TI ITOS chip Can I find less expensive once sure but I want something that I know will work and I know that TI when they're making these They're making these for companies doing voice assistant. This isn't a new thing TI and Burr Brown have been doing this for a long time, so I Trust that I'll be able to get good data out of it. I won't have to worry about You know as long as I follow their layout I won't have to worry about noise creeping in or you know like weird configuration settings So this chip is really cool. I was really psyched to see this. So I picked this up and Here's the breakout but I'm designing for it to get started with experimentation so because I don't need to write a driver for it, I can Start up a Raspberry Pi and just load up this simple alsa I2s driver with quad inputs and TDM map you know TDM Multiplexing and then I can just pipe the data in and I'm going to see hopefully it'll just work And that'll be really cool because I don't want to have to do with the cradle driver if I don't have to so that's my great search chip Today's tip is always look for similar chips Even if the part number is not the same you might find something better than what you've already found 1840 digging it