Matrix 32x16 - Lines held low

[KevKDeV]

I've ported (OK, all warranties no longer in effect) the Arduino library code for the 32x16 LED Matrix product. After some troubleshooting, I'm getting close to the matrix to function properly.

As part of my tests, I'm looking at all signals (clk, latch, oe; A-C; R/G/B). When the cable IS NOT connected to the matrix, all signals behave as expected (except maybe timing, but I'm not optimizing yet). The clk signal is clocking; the latch/oe are toggling; the A-C row indicators are counting up; the RGB lines are correlated to the specified fill color.

However, when I attach the cable to the matrix, the OE and C lines are held low. For now the OE being held low is a nuisance (flickering), but not having C only illuminates half the board.

I tried a 2nd board, and I get the same results.

Without a schematic, it's a bit tough to trace (do you guys have one I can get?). Any suggestions on where to start?

FYI: PIC24/32 MHz/PORTE is data/PORTD has control signals. Timer set to 200 Hz intervals.

[pburgess]

Haven't used these with PIC before, so these might be graspy-strawy suggestions...

1. I'd start by double-checking the ribbon connections...it's real easy to get some lines 'mirrored' when looking at the plug end rather than the socket.
2. If you have a second matrix...try swapping the ribbon cables. I've had one where the IDC connector was pinched wrong and had to be repaired, might be worth checking.
3. 5V or 3.3V microcontroller?
4. Do you have access to an Arduino that you can borrow? Since we know the code works there, this may help in diagnosing the problem (with two matrices misbehaving the same way, I'm more skeptical that the issue is there).