Hi Rob, first, thanks for the support.
We’ve used LW20/SER for quite some time, and now are trying to get the 20/C to work reliably on ArduCopter. The upgrade tool is helpful for getting them to work with current firmware, however, I’ve encountered some worrying power-related problems with it.
After installing the 1.1.3 firmware and setting serial or “serial with legacy banner” mode, the 20/C becomes readable on the Telem 1 port. However, it does not work on any other serial port, and I discovered that this is because it overdraws the supply power. The Telem 1 port has a dedicated 1.5A supply meant for radio transmitters, so the 20/C works. However, in this configuration, the Pixhawk fails to boot via USB: the bootloader is not recognized as a device, and the Pixhawk does not attempt to boot normally. I am uncertain yet whether it is overdrawing my USB port, or if the overcurrent is internal to the Pixhawk.
I can boot via USB with the lidar unplugged, then plug it in after the Pixhawk is booted. It works normally in this case.
When the lidar is plugged into any other serial or I2C port, it instantly overdraws the peripheral power supply. This is visible in these disarmed logs:
The only other device plugged into the Pixhawk 2.1 was a HERE GNSS. The 2.1’s peripheral ports share a 0.5A supply, this means that the 20/C is demanding more than 500 mA by itself! This was not true with the previous LW20/SER and /I2C devices. I have tested three 20/C devices on two Pixhawk 2.1s with the same results.
Interestingly, the “wait for interface” mode appears to work with the existing serial driver in Copter 3.5.7. I’ve tested it quite a bit and it didn’t always work, but I think the power issues were confounding my results. I will test further to see if this mode will work reliably, however the power problems seems to be a critical issue.