M1 PCB errata and changes
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Revision as of 08:13, 11 September 2011 by Admin
 RC1 errata and areas of improvements
 Major errors
These errors prevent parts of the unmodified board from working.
- Connect P[15:8] instead of P[7:0] on the video decoder chip U21
- The MIDI optoisolator is not suitable. Replace it with a 6N138S/6N138_X007 and lower R54 to 120 ohms. Connect pin 8 to 3.3V and leave pin 7 unconnected.
- For USB to work reliably, 15K pull down resistors must be installed on the D+ and D- lines of each USB port (between the 24 ohm resistors and the ports). Add the possibility to make them pull-up resistors to 3.3V (i.e. add placeholders for pull-ups) so the USB ports could work in device mode with a small PCB modification.
 Manufacturing issues
- The installed IR detectors do not work.
- R39 and R30 are swapped (no symptom).
- R147, R148 and R150 are missing (unreliable DDC).
 Minor errors and improvements
These errors do not alter the functionality of the board.
- Add 1K pull-down resistor on ETH_RESET_N (specification says reset should be low during power-up)
- Add 1K pull-down resistor on VIDEOIN_RESET_N (the application schematics includes external POR circuitry)
- Add notch to mark pin 1 of J3 on silkscreen
- Use red, green and blue connectors for J18
- We might want a larger soldered area under the pads of U10
- Indicate "+/- 5%" and pinout (positive in the middle) near J11 on silkscreen
- Add a 5V supply pin on the GPIO expansion header
- Add a test point at the output of the MIDI optoisolator
- Add test points on the USB signals (3.3V FPGA side: VP, VM, RCV, OE)
- To reduce audio output noise, power the LM4550 analog supply through an additional TPS76301 set to 4.3V.
- In order to be able to detect board revisions, route 4 FPGA I/O pins to placeholders for 0402 pull-up resistors. The combination of placed and non-placed resistors encodes the board revision. The RC2 board should be encoded as 0001 (ie place only 1 resistor) to distinguish it from RC1 which does not have any resistor. Use 1K resistors for pull-ups.
- Improve power supply immunity:
- Use at least one via for each power or ground pin of the FPGA (i.e. no via sharing)
- Add more and bigger decoupling capacitors and more power vias around the SDRAM
- Use several vias to connect decoupling capacitors whenever possible, especially the big ones (>= 10uF)
- Add a 0402 capacitor placeholder between PROGRAM_B and ground to be able to delay FPGA configuration if needed
- Indicate "Not 5V tolerant" near J21 (GPIO expansion header)
 RC2 errata and areas of improvements
- Power supply overvoltage and reversed polarity protection
- Video input overvoltage protection
- Reduce video input antialias filter capacitors to 120pF
- Switch to WM9707 codec for improved audio quality
- Fix intermittent "no FPGA configuration at power-up" problem
- Use SMD crystal for video input
- Bigger Milkymist logo