some time ago Ian was so kind and sent me a free QFP proto board , and now here is my "free PCB build" of it :) The build instructions and part list for the free PCB were a bit vague, until I figured out that it was meant to be a POKEY player ;)
Joking aside, there are one or two things which could be improved on the QFP board: The "fixed" pads of the QFT footprint (on the two sides where the pins of the IC are placed regardless of the pin count used) are a bit short, so heating them up with the soldering iron is a bit hard. Also the holes in the proto-area are quite small. I had to make most of them bigger with a fret saw, which was a bit painful, but doable.
The stereo headphone jack is located at the top left side next to the blue potentiometer which is used to digitally control the volume. A small power switch and the Pause/Play button is at the top right side. The other two buttons select the Next/Previous tune. About 60 tunes worth of over 2 hours of music are stored in the 512 kB flash memory of the PIC32.
The headphones are driven directly with a 38 kHz PWM. Two Schottky diodes are used to cut off the negative spikes from the headphone coils. To decouple the audio output from the quite noisy supply voltage (caused by heavy MCU switching), a 74LS32 logic IC is provided with its own 3.0 V LDO regulator. This way a very clean and noise free audio signal is achieved.
The board is supplied via the ICSP pins by directly connecting a LiPo battery . When fully charged, the voltage is a bit higher than the maximum supply voltage specified in the PIC32 data sheet, but it seems to be not an issue in practice. The LiPo is held in place by a double sided sticky tape, and protected from the PCB soldering joints by a thin plastic foil. For ergonomic reasons I screwed some foam rubber onto two nuts which I soldered to the PCB beforehand.
As always, the source code and the full schematic is attached in the .zip file. (P.S.: After discovering not just one but two (!) bugs in the 'C32 v2.0x' and 'XC32 v1.00' compilers (already approved by Microchip and hopefully being fixed in a future release) I went back to the 'C32 v1.10(B)' compiler and the old MPLAB IDE, which also feels faster and snappier compared to the new MPLAB X IDE written in Java.)
A YouTube video is available here: http://youtu.be/PmmKpeFzlGQ
 http://www.seeedstudio.com/depot/qfp-su ... p-786.html
 http://www.seeedstudio.com/depot/lithiu ... p-593.html