[dgryski]

I wrote these tests while checking the Arduino Uno R4 UART driver in #6015. They only use the default serial port, so they seemed useful for other boards too.

tools/uart-test has a host runner and a few small TinyGo programs. The runner flashes each program with tinygo flash, then checks the output over the board's serial port. It builds with the standard Go compiler and uses go.bug.st/serial.

go run ./tools/uart-test -target <target>

Tests:

• echo: bytes sent to the board come back unchanged
• burst: overflowing the RX buffer keeps the first bytes and receiving still works
• seq: 2000 numbered lines arrive in order
• bytes: all 256 byte values arrive intact
• conc: serial output and input work together with goroutines and allocation

I ran all of them on an Arduino Uno R4 WiFi and they pass. The programs also compile for the pico, feather-m4, arduino-nano33 and stm32f4disco, but I have only run them on the R4.

Does tools make sense for this? I'm happy to move it somewhere else in this repo, or to another repo such as tinygo-org/drivers, if that fits better. I'm also fine with dropping it if it isn't wanted.

[dgryski]

I ran these tests on more boards.

Board	Target	Serial	echo	burst	seq	bytes	conc
Arduino Uno R4 WiFi	arduino-uno-r4-wifi	UART through the ESP32-S3 bridge (with #6015)	pass	pass	pass	pass	pass
Arduino Nano (clone, ATmega328P)	arduino-nano	UART through a USB-serial chip	pass	pass	pass	pass	not supported, AVR has no goroutine scheduler
Raspberry Pi Pico 2 W	pico2-w	USB CDC	pass	pass	pass	pass	pass
Raspberry Pi Pico 2	pico2	USB CDC	pass	pass	pass	pass	pass
Raspberry Pi Pico	pico	USB CDC	pass	pass	pass	pass	pass
Seeed XIAO M0 (SAMD21)	xiao	USB CDC	pass	pass	pass	pass	fail

The conc failure on the XIAO is a bug in the SAMD USB driver that these tests found. The fix is in #6024.

The Nano needed the second commit in this PR, which sets the baud rate to 115200 so that boards with a different default baud rate work.

The RX buffer size differs by board, 32 bytes on the Nano, 128 on the R4 UART and 512 on the USB CDC boards. The burst test does not depend on the size.

[davecheney]

LGTM. I love the idea

[dgryski]

I'm building a larger test suite with the serial tests as one part. Currently stalled on that because of a reproducible hang on pico2 when trying to run the new tests. Let's hold off on merging this one until I'm happy with the newer tests or decide they're not worth it.