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HUB75 led matrix
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This is an example capture of a 32x32 pixel 1/16 scan "normally addressed"
HUB75 LED matrix. The matrix is being driven by a Raspberry Pi 3b+ with
https://github.com/hzeller/rpi-rgb-led-matrix at 12 PWM bits per color.

The A, B, C and D lines are address lines that select two rows at a time that
can have LEDs on. Address 0 selects rows 0 and 16, address 2 selects row
1 and 17, and so on.

R1, G1 and B1 lines are binary data on the different color LEDs on the first
line and R2, G2 and B2 for the second line. The data is clocked into constant
current driver chips that act like 74595 shift registers.

It is possible to build bigger displays by chaining the data to more panels.


Logic analyzer setup
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The logic analyzer used was a DreamSourceLab DSLogic Plus (at 100MHz):

  Probe       HUB75 signal
  ------------------------
  0           CLK
  1           #OE
  2           LATCH
  3           no connection
  4           A
  5           B
  6           C
  7           D
  8           R1
  9           G1
  10          B1
  11          no connection
  12          R2
  13          G2
  14          B2
  15          no connection