2/17/2026 9 AM - Planned the BOM and made the schematic

I first started off researching what components my MP3 player would have. I knew from the start that I wanted this to be really tiny and also simple enough for me to make it. Since i already had the schematics for the XIAO Seeed Studio ESP32C3 and because it is tiny and a pretty good board for my project I decided to use it! Then I used a MAX98357A for the DAC because it seemed simple enough and also was cheap in my country compared to the other alternatives. Then the normal components like the SD Card reader, switches, the battery situation and the headphone jack were all just generic stuff. I used KiCad for the PCB!

So I started by collecting all the schematic symbols. The ESP32 was already with me from the Macropad project so that was done. I also found a MAX98357A schematic symbol but it ended up being just the chip and not the board which i was using so i had to change it in the end to a generic 1x2 connector and 1x7 connector. Then for the SD card reader I again used just a 1x6 connector. For the headphone jack i actually found a really cool schematic symbol and footprint on github but it was in an older file format so I spent a while trying to break my head converting it to the latest one when it was just a simple process in KiCad. Then I started connecting all the components. I had some trouble connecting the headphone jack so I employed Google Gemini to help me with that part. Then I started assigning footprints to the entire thing.

Challenges:
I spent way too much time using the wrong schematic symbol for the MAX98357A and the headphone jack so I had to rewire stuff a lot. Then I tried making my own footprint for the MAX98357A but I wasn't that smart enough yet so i had to drop that in the middle.

2/17/2026 10 AM - Changed the schematic and Routed the PCB

I had to change the wiring of the headphone jack to prevent it from shorting.
Then I started working on the PCB. I imported all the components from the schematic and I placed it all in their correct positions on the PCB. I then used my own grid settings to place the 1x2 connector in the correct position with respect to the other 1x7 connector for the DAC. I then routed everything! I also made the audio output routes thick for it to be more clear? Hopefully it is.

2/17/2026 11 AM - Rerouted PCB and started making the case

I rerouted parts of the pcb to make sure that it looks good and also works properly.

Then i started taking measurements for the case! I noted them down and used Fusion 360 to make it!
I used the split body tool to make the top of the case!

2/17/2026 12 PM - Finished case CAD and assigned CAD models to PCB

I finished making he CAD Model!

Then I started assigning all the 3D models to the PCB! I found a model for the ESP32 and the SD Card Reader Module on a random website and for the Headphone Jack I used the same Github page! I tried finding the model for the exact same DAC i had but it was nowhere to be found so I think I'll have to make my own model! I also found a model for the battery which I'll add to the assembly file!

2/17/2026 2:05 PM - Assembled all the components in CAD

I looked at all the PCB Manufacturers that ship to my country and uploaded my pcb to all of it and decided on the cheapest which is the Seeed Fusion One-Stop PCB Assembly service and it came up to about 12 dollars. Most of the others were also about this much but Seeed Studio offered 10 boards while the rest only offered 5 for the same price.

I then got the step file of my pcb and i imported it into the CAD Case. I quickly ran into a few errors so I made another file with JUST the pcb and imported the case into that file as a derive. This way i can switch back to the case file and make changes as needed. I added the SD card slot and also chanegd the fillets a bit to accommodate the fill pcb. I also noticed that the headphone jack would be in the middle of the DAC so hopefully the DAC is thin enough to fit on top of the jack.

2/17/2026 2:40 PM - Added all components of the PCB to CAD

I improvised and added two blocks of different colors based on the exact dimensions of the DAC (Yellow) and the Battery (Red). The DAC barely fits over the headphone jack but since it fits I'll leave it as is and not change the PCB again.

I also increased the height of the case by a lot and changed the holes around. I still have to add a slide switch hole for the main on/off control for the MP3 Player!

2/17/2026 10:25 PM - Failed at writing the Firmware, Changed the schematic a lot!

I did a lot and I learnt a lot. I spent about 1.5-2 hours just trying to get the firmware correct. I used VS Code and it did not come out perfectly. I then switched to the Arduino IDE and that too gave me lots of problems. I asked AI to help and it got nowhere. I even tried the web based version of Arduino IDE. Nothing worked. So i asked a friend and he looked at my schematic and told me that it wouldn't work at all and that my DAC was wrong and i had to use a PCM5102 instead. This was when i had an epiphany and realized i could make both an MP3 Player and an Mp3 Speaker! So I duplicated the schematic and i changed up the parts for the speaker and parts for the player!! I'll use mouse bites in the final PCB so I can have then separately!

2/17/2026 10:43 PM - Worked on the PCB

Moved all the components to their correct locations on the PCB! I'll do the rest tomorrow ;-; I again used the custom grid I made for the DAC and made sure the 1x2 and 1x7 connectors were in the correct positions relative to each other

2/18/2026 10 AM - I routed the PCB (Again T-T)

I routed everything in the PCB except the GND pins. Then I traced the edges and added mouse bites for both the boards separately. I used the "Draw Filled Zones" tool to make sure no copper ends up in the tab. Then i poured copper as the ground on the back copper layer for both the boards. I had to assign the XIAO 3D model again for some reason and I did that too! The mouse bites were from github!

2/18/2026 12 PM - Made CAD Case for both boards!

I made the case for the two different boards in CAD! I had to import a modified version of the PCB with the two boards separate so that it's easier for me to make the case for. I followed the same method like the previous case by splitting the bottom to make the cover and adding holes for the screws. Then cutting out the sides and the top for the buttons. I also assembled the PCB inside the case with a few placeholder blocks for the parts I couldn't find a 3D model for.

2/18/2026 4 PM - Made the BOM and finished the GITHUB page

I finally got to making the BOM. I looked through a bunch of websites and decided to buy off two websites Robu and Hubtronics. I also added Amazon.in after finding my capacitors only there. Then I looked for the PCB fab because the Seeed Studio one was too expensive. I ended up with AllPCB which had an offer and i got my PCB for just 5 USD which is great! I then added all my files to a folder and created a Github repo and uploaded all of it there. Then I added a README and finished it! Time to submit!!