I'm using a Raspberry Pi 3 model B+ together with a Waveshare touch screen model 7inch HDMI LCD (C) which claims to be “low consumption,” although gives no precise amperage of the device.
Anyway, sometimes the Raspberry Pi boots correctly, but more often than not (say nine times out of ten) it shows a lot of USB-related errors in syslog, and the monitor is powered correctly, but the touch part doesn't work.
The errors look like this:
usb 1-1.3: device not accepting address 14, error -32
usb 1-1-port3: unable to enumerate USB device
or:
usb 1-1.3: device descriptor read/64, error -32
usb 1-1-port3: attempt power cycle
Searching through the Internet, I find a lot of resources suggesting three things.
Some claim that the fault is the power supply. I tried to power the Raspberry Pi with (1) a 2.4A charger, (2) a 3A charger, and (3) a 5V 12A power supply. While I understand that a 2.4A charger may not be ideal, the 12A PSU should be largely enough. I also tested different USB cables.
Others suggest to put one or all options among
dwc_otg.fiq_fsm_enable=0,dwc_otg.fiq_enable=0, anddwc_otg.nak_holdoff=0. I tried to put all three, although I cannot find any relevant information about what those options are, and don't know what they really do. Anyway, I observed no difference.Others assert that it is “triggered when power consumption from the port is too high.” Possible, although I'm surprised that a few LEDs for screen backlighting and the touch itself is too much for Raspberry Pi (as the screen itself gets its main power rather through HDMI).
Also, there are mentions of other reasons, such as a wrong frequency or damaged USB device. Regarding the frequency, I did the test with another, brand new Raspberry Pi 3 B+, and the result is still the same. Damaged touch screen? Possible, but weird.
Finally, a few resources mention
max_usb_current=1setting in/boot/config.txt. I already have this setting, given that I'm not sure if I should, after all.
So, what are my options?
