An update and some good and bad news.
First the bad.
I've distilled the failure mode to the following:
1. If aplay is used to send to the rig, it's successful.
aplay -D CARD=Device,DEV=0 /usr/share/sounds/alsa/Noise.wav
2. If one of the uart devices is opened, aplay fails.
cat /dev/ttyUSB0
aplay -D CARD=Device,DEV=0 /usr/share/sounds/alsa/Noise.wav
Syslog doesn't show anything interesting.
Jul 29 11:31:41 wsjtx kernel: usb 3-1.2: reset full-speed USB device number
4 using xhci-hcd
Jul 29 11:31:41 wsjtx systemd[996]: Reached target sound.target - Sound
Card.
Wireshark shows a "protocol error" after the first 3 iso transfers. It
claims that it's reported from end point 7. There is no end point 7.
I enabled the trace in the driver (xhci_hcd) and it reports a "USB
Transaction Error" from the controller. It says it's from end point 15.
There isn't an end point 15 either. That error is reported as a
"protocol error" to the application that called the driver.
Since the same xhci_hcd driver works with other xhci compliant
controllers, my conclusion is that the bug is in the
Synopsis/Designware core. That core is used by both the RPi5's custom
asic as well as the RPi4's Via VL805 USB controller. I'll need a bus
analyzer to see what's actually on the wire. If I can get some more
detail, I'll report it to Raspberrypi. Maybe it can be fixed in the
controller firmware. I'm not too hopeful.
The good news is that the Broadcom SOC's USB controller on both the
RPi4&5 is connected to the usb-c power connector. If power is supplied
via the header, that port can be used as a host. It uses the dwc2
driver which is enabled by adding "dtoverlay=dwc2,dr_mode=host" to the
end of /boot/firmware/config.txt. You also need a usb-c to usb-b cable
to attach to the rig. I tested this on both an RPi 4 and 5. A CQ from
wsjtx posted lots of flags on pskreporter.
As an alternative to applying power via the header, there are
commercial power splitters designed for the RPi4 that may be more tidy.
I haven't tried any.
Steve WA9OLA
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