GPi LED driver troubleshooting notes

Now I have connected the GPi's Digit enable and 7 segment signals to the logic shifter and buffer board.  I first test the digit enable signals, with the 7 segments all on and found it OK.  Then I connected the the gz_led_demo outputs but found the display weird.

I guess there are two reasons.

(3) I have inverted the segment signals by the ULN2803, so the display is on/off inverted.

(2) The ULN2803 hardware has something thing wrong.

Time for a break.

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