Audio Codec daughterboard for I2S

[blmorris]

I've been working on getting I2S (Inter-IC-Sound) support working in uPy for a little while now - it is progressing in fits and starts, as my time allows. I have gotten audio tracks to play correctly, so I'm confident that I'll have it all working correctly soon enough

I have spent a few days designing a daughterboard for the pyboard with an I2S codec so that other users can play around with audio in MicroPython once it gets integrated. I am keeping the design simple and only using parts that I have used before, as I expect to make a relatively small number at first and I will be making them by hand. The boards will have 3.5mm stereo jacks for input and output; the audio codec is the SSM2604 from ADI, and the output amplifier is the TPA6130A2 which will allow the board to either directly drive headphones, or to drive a line-out to another amplifier. Both chips will be controlled via I2C.

The design is nearly completed; I am thinking of adding a small thumwheel potentiometer to connect to an ADC for gain control, and maybe an option to connect a pair of electret microphones instead of an audio line-in. There is a bit of room left on the board, and these options will add a minimal cost.

Anyone interested in this? I am planning to wrap up the design and submit it to OSH Park in the next day or so; I expect to be able to make and sell them for about $20 US (building by hand, so I won't be making much on the labor!) but it will be well worth it to me if it allows anyone else to play around with I2S.

Feel free to reply here or to PM me with any questions. I will post a board image and schematic shortly.

-Bryan

[danicampora]

Hey Bryan!

I am definitely interested in getting one! please count me in

Cheers,
Daniel

[dhylands]

I'd be interested in one (no specific reason right now - but making noise sounds like fun)

[blmorris]

Dave and Daniel - I'm glad you guys are interested!

I just pushed my Eagle project to GitHub: https://github.com/blmorris/uPy_AudioCodec

If you want to check it out and don't have Eagle, I provided PDF's of the schematic and board.

If I can't think of anything that I have missed, I'll place the order with OSH Park later today. It's my first time ordering boards with them; if I understand their pricing correctly it should be a little less than $3.50 US per board, ordered in multiples of 3. Pretty amazing for doing small runs, but of course you need to wait a bit…

-Bryan

[blmorris]

Update: I received the boards last week and I have a couple built up and tested - all good so far, so I'm planning to build a few more and get them in the mail shortly.

Audio codec daughterboard

image2.JPG (186.34 KiB) Viewed 6932 times

I want to make a few comments about OSH Park, which I will definitely be using again.
I was very impressed by how easy it is to use their service, and they delivered quite a bit faster than their stated lead-time: they promise to ship within 12 business days of receiving the order; I had my boards in hand (via USPS Priority Mail) 13 actual days after placing the order. EDIT: The webpage actually says calendar days; not sure why I was so certain it was business days. Anyway, it just means that they turn orders around this fast routinely, which is even better.

I am in the habit of putting important information (my name, date, the name of the board) in the top or bottom copper layer rather than in the silkscreen - it just seems more durable that way. Unfortunately, text in the copper layer is very difficult to read through OSH Park's nearly opaque purple solder-mask layer. What I didn't realize until I ordered is that they offer a bottom silkscreen layer at no additional charge - with no components on the underside of the board, I could have written a short novel there. Live and learn…

-Bryan

[danicampora]

Very nice Bryan Good job!