FlushCDC Problem with arduino-pico core

[s-t-e-p-a-n-o-v]

Operating System

Windows 10

IDE version

1.8.19

Board

Raspberry PICO

ArduinoCore version

2.3.3

TinyUSB Library version

1.14.1

Sketch (attached txt file)

#include <Adafruit_TinyUSB.h>

void setup() {
  Serial.begin(115200);
}

void loop() {
  Serial.println("blink!");
  delay(200);               
}

What happened ?

Even/odd loop iteration doesn't send data to PC. Data is stored in buffer and transferred on next loop cycle.

How to reproduce ?

Compile and upload sketch with arduino-pico core with TinyUSB stack and open serial port monitor.

Debug Log

No response

Screenshots

[s-t-e-p-a-n-o-v]

It's hard to find where bug is, inside arduino-pico core calls or inside TinyUSB. Corresponding issue at arduino-pico repository https://github.com/earlephilhower/arduino-pico/issues/720

[karelv]

Windows 10 / IDE 1.8.19 / Pico 2.4.0 Adafruit trinkey QT2040

--> Time steps of 400ms (in pairs of two)

I observe the same behavior as @s-t-e-p-a-n-o-v

[karelv]

Here is with pico sdk: (I removed the include statement)

--> Time steps of 200ms.

[karelv]

In my project (fairly large code base), my observation is that the some routines make the serial interface crashing. Only some particular (application-)commands are working. Switching to pico SDK, let all work nicely. I want to use the combination of MSC and UART. This is why I want to use adafruit TinyUSB stack.
Note: I disabled the MSC device already w/ tinyUSB, no improvement.

[karelv]

:+1:

[karelv]

I tried 1.14.1 and 1.14.3 of this lib, both have same issue.

[pschatzmann]

I don't quite understand why this should be an issue. If you want to force the output just call Serial.flush();

A possible solution would be to add a flush(); and yield(); at the end of size_t Adafruit_USBD_CDC::write(const uint8_t *buffer, size_t size)