I'm trying to get a Pi Zero W to talk to a MAX7219 LED driver over SPI using spidev-3.4 and the Python max7219 library v0.2.3, but the LED driver doesn't respond and the data coming out of the SPI0 port when running the included example looks very odd:
While I'm somewhat new to using the SPI port that just doesn't seem right, and my scope doesn't detect any valid data either. By contrast, when I compile and run spidev-test.c I get something quite different, which my scope readily decodes:
Does this issue look familiar to anyone?
Edit: Forgot to mention, the measurements were taken upstream of a 3.3-5V level converter (needed for the MAX7219), hence the 5V range. And to clarify, the blue channel in the images above shows the SPI0 MOSI data line (BCM #10), the red is SPI0 SCLK (BCM #11), and the green SPI0 CE0 (BCM #8). One notable oddity with the first sample, apart from the lack of any discernable data, is that the clock looks very weak; it barely reaches 2V. Finally, in case anyone's wondering, absolutely nothing was changed between capturing these samples; all wiring remained unchanged, so did the settings on my scope, and the configuration of the Pi - the only thing altered is the command executed (python sevensegment_test.py vs ./spidev_test -D /dev/spidev0.0).