RGB Matrix Backpack

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The RGB Matrix Backpack will be a small controller board to attach to 8x8 RGB LED matrices. It will accept input via SPI or I2C and control the display.

Project Status

2012-03-14: Jammies is releasing the SparkleShiny which does everything this was going to plus more. Cancelling this project. 2010: Revision 1 board assembled, troubleshooting and writing code now.

Rough Notes

  • Going to use the PIC18F65K22 as it will drive all the pins needed directly (no muxes or anything) and is <$5 in single qty. Cheaper than using multiplexers and more flexible this way.
    • Also I haven't used PICs in any projects in ~5 years, so I want to try them out again :)
  • Cathode/low side (columns) will be N-channel MOSFETs.
    • Which is nice because there are 24 columns to drive, but only 8 rows. Cheaper components on the columns is handy.
  • Anode/high side (rows) should be a constant current source with P-channel MOSFETs.
  • Being able to plug them together in a 2D matrix would be awesome
  • They plug into a 1D matrix natively, and there's a cable interface to link multiple 1D rows together into a 2D display

Revision 1 Notes

  • Silkscreen on inter-board connectors is incorrect on some
  • Constant current regulator not implemented properly, output should be on the far side of the current sense resistor, not the near side
  • Constant current regulator uses an LM317 (3V dropout) which won't work for the green/blue LEDs because they need 3.3v max
  • The MOSFETs are a huge pain to solder properly, and there's lots of free board space available for larger ones