switch to i2s amp & added LDO to vbus#1
Conversation
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Oh cool - thanks for working on this. As it turns out I've been poking at this too - I've got a schematic in the works with a MAX98357A I2S amp and a TPS63031DSKR true 3.3V buck/boost regulator. Parts are coming tomorrow and I hope to get the board off to fab this week. |
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Oh - BTW: very interested in how an LCSC / JLCPCB build works out. |
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ah nice! boost buck is probably the way to go, why have 2 solutions when you could have one. I also started playing with that max amp, and it is supported by circuitpython - you've probably already laid out the board, but there is a restriction with the circuitpython i2s rp2040 lib where the pins need to be sequential and in this order: BCLK, LRCLK ... I'm not sure if DIN needs to come after those two sequentially or not, but may as well. I should probably start a different thread, but I tried importing the BOM that you uploaded to octopart, and it seemed like it was for a different project entirely. |
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My current schematic for the I2S amp has BCLK, LRCLK, SDO on GPIO16,17,18 respectively - I had noticed that limitation on putting the signals adjacent a while back - it's a PIO thing IIRC, not just CircuitPython. No idea what's going on with the BOM. I'll look into it later today. |
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Here's a PDF of the revised schematic I'm working on - I'm not sure how I want to handle this in git - maybe start a separate I2S branch. |
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No idea where that Octopart BOM you're looking at came from - it wasn't me. The BOM I generated is in this git repo only. |
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ah, I just meant I used octopart to open the ods file, not that there was already one on octopart - I just installed openoffice and it worked fine though :) new schematic looks good! |
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OK - Octopart probably doesn't like the way my BOM .ods is formatted. I wasn't targeting their service, just using the defaults from the Kicad BOM .csv output. |
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I setup the bom with JLC / LCSC numbers. I still need to replace the push button with something from their library, and would require hand soldering for the side button and pot. Bunch of "extended parts" required unfortunately. |
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Yeah, I haven't started work on the layout yet. I'm swapping the thru-hole connectors (serial, SWD, spkr, batt) out for smaller SMD parts to reduce size and avoid interference with the speaker on the backside so there will be a bit more work to do. Yours looks great though and I'm looking forward to how you get the BOM & manufacturing stuff going. |
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Got a preliminary layout going - using some little connectors for the battery & speaker plus removed some pins from the SWD connector. Note that there are no LC filters on the speaker outputs - datasheet says that's not needed even though the Adafruit breakout does provide them. Not sure if that's a problem or not. |
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nice - I finished my layout as well, and sent it off for assembly
I added a big resistor to the gain select for the amp, switched to usbc, and setup the debug header so you can just plug a pi pico into it directly (my preferred approach) I'm curious to see how bad this back of the board interfering with speaker is - hopefully something that can be solved with hot glue or tape. |
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Looking fwd to seeing how your assy turns out. I've been tweaking on my layout for a few days and here's what it looks like ATM: I'd be interested to get a look at your BOM and assembly order - curious to see what it would take to get my design done vs having to build my own. |
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Added LCSC part numbers to my schematic - there are quite a few "extended" parts on the list, which cost an extra 3 dollars each per assembly order, but you can skip past those and just do them by hand. |
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Cool - thanks! |
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I haven't tested this at all, I'm planning on marking it all up with lcsc part numbers and getting it assembled. Feel free to ignore! this is just a ping to let you know I'm poking at this.