I finally had some luck getting two ADXL345’s detected at once on a single Raspi. A Raspberry Pi 4B to be specific.
The issues seems to be that SPI0 and SPI1 are “special” and also kind of dumb on the Raspi. SPI 0 & 1 use a separate (legacy I think) controller versus 2-6 which were added to the latter Pi’s. SPI 0 & 1 can be enabled at the same time, but SPI 1 doesn’t support the necessary signaling mode that Klipper needs, so it fails if you try to use it.
SPI 0 works, but enabling it is a trap. If SPI 0 is enabled, SPI’s 2-6 don’t work properly. I’d originally tried combinations of SPI 0 & 1 (fails) as well as 0 & 5 (fails differently). 5 uses the same pins as 1, so that was convenient (no rewiring), but 5 fails if 0 is enabled.
I finally hooked my two ADXL345’s to SPI 5 and 6, and that works! It seems Klipper has a problem finding those though, so I also needed some symlinks to pretend they’re really 0 and 1. So all in, I have:
accel_chip_x: adxl345 hotend
accel_chip_y: adxl345 bed
And I had to create symlinks in /dev (re-created each time by klipper’s init script) so I have:
pi@octopi:~$ ls -l /dev/spidev*
lrwxrwxrwx 1 root root 14 Sep 14 06:55 /dev/spidev0.0 -> /dev/spidev5.0
lrwxrwxrwx 1 root root 14 Sep 14 06:55 /dev/spidev1.0 -> /dev/spidev6.0
crw------- 1 root root 153, 0 Jul 20 07:39 /dev/spidev5.0
crw------- 1 root root 153, 1 Jul 20 07:39 /dev/spidev6.0
If I just put 5 & 6 directly in printer.cfg, startup of the raspberry mcu device fails. I’m printing at the moment unfortunately, so I can’t reproduce that error.
With the symlinks, all is happy. I can run resonance tests on either probe without rewiring or changing any configuration.