M1 PCB errata and changes

From Milkymist Wiki

Jump to: navigation, search

Contents

[edit] RC1 errata and areas of improvements

[edit] 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.

[edit] Manufacturing issues

  • The installed IR detectors do not work.
  • R39 and R30 are swapped (no symptom).
  • R147, R148 and R150 are missing (unreliable DDC).

[edit] 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)

[edit] 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
Retrieved from "http://milkymist.org/wiki/index.php?title=M1_PCB_errata_and_changes"
Personal tools