TinyGo is broken on xiao-esp32c3 (TinyGo 0.41)

[nodebotgithub]

Tested using:

• Macbook Pro M1 Max, Sequoia 15.7.4
• XIAO ESP32 C3
• Go 1.26+
• TinyGo 0.41

Simple TinyGo project that prints text in a loop does not work in XIAO ESP32 C3. I confirmed that the same environment work using Arduino CLI and MicroPython. I think TinyGo implementation on XIAO ESP32 C3 is broken.

Here is the minimally reproducible bug

https://github.com/nodebotgithub/tinygo-serial-bug

[nodebotgithub]

I also tested this on XIAO ESP32 S3, also not working. I wonder what am I doing wrong.

[sago35]

As of TinyGo 0.41.1, only the samd21, samd51, nrf52840, rp2040, and rp2350 support USB CDC.

https://github.com/tinygo-org/tinygo/blob/release/src%2Fmachine%2Fusb.go

On unsupported microcontrollers, machine.Serial is configured for UART rather than USB CDC.

[sago35]

If you look closely, it seems that the ESP32-C3 and ESP32-S3 support USB CDC. I'll check that out later.

[nodebotgithub]

If you look closely, it seems that the ESP32-C3 and ESP32-S3 support USB CDC. I'll check that out later.

Yes indeed. I checked. Also, the examples here clearly said ESP32 C3 as well
https://github.com/tinygo-org/tinygo-xiao-examples

[nodebotgithub]

I escalated this issue also to Seed TechSupport Team. They were able to reproduce it. Will report back here once I get more clarity.

[nodebotgithub]

Seeed TechSupport Team got back to me. Temporary workaround suggested (for the minimally reproducible repo above):

1. Run make flash-tinygo
2. Run make monitor
3. Briefly press and release the RST button. This might makes monitor disconnects, but just run make monitor again, and you'll see the tick message running

More clarity on the fix from the Seeed team:

For comparison, TinyGo 0.41.1 bundles espflasher v0.6.0. We flashed the same TinyGo firmware using the standalone
espflasher v0.8.0, and the board reset and started producing serial output automatically without requiring a manual
reset.
Our test results suggest that the behavior is related to the flashing/reset sequence, particularly the DTR handling in
the older flasher, rather than the XIAO hardware or the compiled TinyGo application.

[nodebotgithub]

@sago35 It seems current dev branch already has espflasher v0.8.0 so this should be fixed on next release.