procedure for sleep/wake of USB device w/TinyUSB?

[myklemykle]

Hi,

I'm using TinyUSB on the RP2040 with Earle Philhower's Arduino-pico core, and I'm trying to work out the best procedure for sleeping & waking the USB subsystem. It goes like this:

to sleep:

  Serial.end(); // halt USB serial port
  pll_deinit(pll_usb); // halt USB clock

to wake:

  pll_init(pll_usb, 1, 1440000000, 6, 5); // return USB clock to 48mhz
  tusb_init();  //Adafruit/TinyUSB usb init
  Serial.begin(115200);

I found that I had to add tusb_init() after restarting the USB clock, or else I got no communication. But I've also found that the USB subsystem can be flaky after I do this. It seems like the more USB Serial data is being sent after sleep/wake, or the sooner after sleep/wake, the more likely that my chip will lock up and reboot. Also the USB host sometimes drops communication after sleep/wake. In that case I can re-establish it by unplugging and replugging the usb cable.

I wonder, am I doing this right? Is this the right procedure for stopping and restarting TinyUSB? I did not find a tusb_deinit() API call to use before sleep. And I just copied tusb_init() out of the arduino-pico startup code, I don't really grok all that it does. Do I need to notify the USB host somehow after wakeup, to trigger a reset of the whole connection?

Much obliged for any advice.
Thanks,
-mykle-