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I am following these instructions to get a simple 7-segment display working:

https://github.com/rm-hull/luma.led_matrix

My problem is that as soon as one of the 3 SPI Pins are connected the digits go off. When running the provided sample script i see no errors, but again, all digits are off. I already double and triple checked the pin-connections and they are as described in the documentation. SPI is also enabled. (Checked with ls -l /dev/spi* ) As long as just 5V and GND is connected, all digits show '8'.

The display works fine when used with an arduino.

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  • According to the datasheet for the MAX7219, all the segments should be off if just power is applied. Feb 10 '19 at 22:49
  • Are you driving the display from the 5v on the Pi, can you post a schematic and/or photos? What's the current drawn by your display (better yet do you have a data sheet)? Are you using a level shifter between the Pi and MAX7219? Feb 19 '19 at 14:14
  • @RogerJones the wiring is exactly as in the documentation here luma-led-matrix.readthedocs.io/en/latest/… no level shifter is used.
    – clamp
    Feb 24 '19 at 9:46
  • I assume then that you've read the "Notes" section and decided not to use a level shifter to interface the 3.3v Pi to the 5v MAX7219 for some reason? luma-led-matrix.readthedocs.io/en/latest/notes.html Feb 24 '19 at 18:18
  • @RogerJones I did not read the Notes section, as I thought it is only relevant for cascading devices. I assume I need such a 2N7000 Transistor, but what is the "Signal" Pin and what is the normal one?
    – clamp
    Feb 25 '19 at 18:06

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