Regards,
Kl3m3n

I have tested the GUI-O fix with Pico and it works.

Waiting for your feedback when new version of GUI-O is released (already in release process).

BR,
Kl3m3n

I will let you know.
Best regards,
Kl3m3n

I then disabled flow control in the test:
Serial.ignoreFlowControl(true)

And GUI-O now works. So I think the problem is you are not asserting the DTR line when using the CDC driver.

[edit]
Since I can see no way to ignore flow control with the mbed core I will await you to change GUI-O to assert DTR. Incase it isn't obvious without DTR (DataTerminalReady) asserted no arduino will send data down a serial connection with flow control enabled, which it is when using the CDC driver.

The official arduino-mbed core hardcodes pid 0x00C0. The unofficial (old) arduino-pico core defaults the pid to 0x000A.

What core did you test with or did you just compile some code with the pico sdk (i.e. not arduino) ?

Anyway I patched arduino-mbed to use 0x000A and I get the same problem, so maybe the problem is the way arduino-mbed configures the tinysub stack is somehow incompatible with your gui-o code?

I'm fairly sure you could replicate this by building a hello world app on platformio using the default arduino platform which is mbed.

FYI the board came from the RPI official shop.

If you exit the GUI-O app and then plug in the Pico, what happens? There should be a pop-up window where you can select an app that can use the Pico device - is GUI-O shown on the list?

Can you try sending the data from Pico to GUI-O without GUI-O sending the @init string first? What happens then?

I also have an original RPi Pico and the Serial USB Terminal reports it as:
Serial device - CDC
Vendor ID:2E8A Name: Raspberry Pi
Product ID:000A Name: Pico

Can you tell me, where you got the Pico? Do you have a link of the store where you've ordered it from?

But I think the quickest way to get some additional information via adb (android debug bridge). I don't know how familiar you are with this, but I will describe the procedure (I will write for Linux, but the procedure for Windows is the same once you install adb):

1. Connect the device to your PC using USB cable
2. Navigate to Settings -> About phone -> and tab Build number / About phone 7 times
3. Go back to Settings and search for Developer options
4. Scroll down to debugging and enable USB debugging and then Wireless debugging
5. You should confirm authorization / pairing
6. Note the <ip_address> and <port>
7. On your PC, run the commands in the terminal (you need to be connected on the same WiFi network on your Android and your PC):

adb disconnect
adb tcpip <port>
adb connect <ip_address>:<port>

After connecting, remove the USB cable and use:

adb devices

You should see the Android device is connected.

Now run:

adb logcat > log_1.txt

This will start logging system messages to a file (named log_1.txt).

Now connect Pico to the Android device and start GUI-O. Try reproducing the issue with Pico and GUI-O. After you've finished this, press Ctrl+C in the terminal to stop the logging. Please send the file to: info.guio.app@gmail.com

Thank you.
Best regards,
Kl3m3n

Again this code works perfectly on nano's, esp32, etc.

version 1.0.92 is out. Can you try and see if it works?

Best regards,
Kl3m3n

I will try to release a new version this week.

Best regards,
Kl3m3n

It seems I don't have the same RPi Pico board as you (Vendor: 2E8A Product: 0005), but it works ok with GUI-O. Which version / revision of RPi do you have?

GUI-O is using the same usb serial library as the "Serial USB Terminal" app, so there is no reason your board shouldn't be compatible.

I can try manually adding the vendor and device id to GUI-O and manually loading the CDC drivers. Also, I will check if i need to update the usb serial library... GUI-O uses version 3.4.6, while the latest version is 3.8.1 (https://github.com/mik3y/usb-serial-for-android/releases).

Best regards,
Kl3m3n

Serial device: CDC
Vendor: 2E8A Name: Arduino
Product: 00C0 Name: RaspberryPi Pico