Undefined SCL and SDA PINs for ESP32

[IngwiePhoenix]

I just wanted to flash a very basic program to an ESP32 and got this error:

PS C:\Users\ingwi\Work\esp32-test> tinygo flash -target=esp32 ./main.go
# machine
C:\Users\ingwi\tinygo\src\machine\machine_esp32_i2c.go:38:16: undefined: SCL_PIN
C:\Users\ingwi\tinygo\src\machine\machine_esp32_i2c.go:41:16: undefined: SDA_PIN

I clearned out the tonygo folder before upgrading.

PS C:\Users\ingwi\Work\esp32-test> tinygo version
tinygo version 0.36.0 windows/amd64 (using go version go1.24.0 and LLVM version 19.1.2)
PS C:\Users\ingwi\Work\esp32-test> go version
go version go1.24.0 windows/amd64

Here is the main.go that I tried to compile:

package main

import (
        "machine"
        "time"
)

var counter int

func handleInterrupt(machine.Interrupt) {
        counter++
}

func main() {
        button := machine.GPIO4 // Change to your desired pin
        button.Configure(machine.PinConfig{Mode: machine.PinInputPullup})

        interrupt := machine.NewInterrupt(button, machine.PinFalling, handleInterrupt)
        interrupt.Enable()

        for {
                println("Counter:", counter)
                time.Sleep(time.Second)
        }
}

The same also happens when I try to use an existing example:

PS C:\Users\ingwi\Work\esp32-test> tinygo flash -target=esp32 examples/blinky1
# machine
C:\Users\ingwi\tinygo\src\machine\machine_esp32_i2c.go:38:16: undefined: SCL_PIN
C:\Users\ingwi\tinygo\src\machine\machine_esp32_i2c.go:41:16: undefined: SDA_PIN

Did I miss anything...?

[eliasnaur]

I don't know if that's a great error message, but I believe the problem is that you're targeting a processor, esp32, and not a board. Since the processor (probably) supports I2C on several pins, there are no default SCL/SDA pins. It will probably work if you target a specific board such as m5stick-c.

[IngwiePhoenix]

Oooooooh that makes sense. Unfortunately specifying esp32 was the closest I got.

This is the board itself: https://www.berrybase.de/esp32-nodemcu-development-board

Basically just the CPU, a USB-to-serial and...a lot of pins. o.o

What'd be a good board to target for this?

[eliasnaur]

I think any board would work. For example, I use the "pico" target for a custom rp2040 board.

[deadprogram]

I think any board would work.

Not exactly, you need to specify a board with the same processor.

In this case, I would try -target=esp32-coreboard-v2

[IngwiePhoenix]

That compiled perfectly! Thank you :) I currently don't have a board at hand but seing that it compiled was already much more than before.

> tinygo flash -x -target=esp32-coreboard-v2 examples/blinky1
ld.lld --gc-sections -L 'C:\Users\ingwi\tinygo' -T targets/esp32.ld -o 'C:\Users\ingwi\AppData\Local\Temp\tinygo1447925070\main' 'C:\Users\ingwi\AppData\Local\Temp\tinygo1447925070\main.o' 'C:\Users\ingwi\AppData\Local\tinygo\compiler-rt-xtensa-esp32\lib.a' 'C:\Users\ingwi\AppData\Local\tinygo\obj-ee0fcbf9b07ff3b3b55126a347ff9538c9c5551af689cc30e921b4c8.bc' 'C:\Users\ingwi\AppData\Local\tinygo\obj-5f10ab9602f3eae48f2a69b42f3858e8b50b626793255d2a390c339f.bc' 'C:\Users\ingwi\AppData\Local\tinygo\picolibc-xtensa-esp32\lib.a' -mllvm -mcpu=esp32 -mllvm -mattr=+atomctl,+bool,+clamps,+coprocessor,+debug,+density,+dfpaccel,+div32,+exception,+fp,+highpriinterrupts,+interrupt,+loop,+mac16,+memctl,+minmax,+miscsr,+mul32,+mul32high,+nsa,+prid,+regprotect,+rvector,+s32c1i,+sext,+threadptr,+timerint,+windowed --lto-O2 '--thinlto-cache-dir=C:\Users\ingwi\AppData\Local\tinygo\thinlto' -mllvm --rotation-max-header-size=0
unable to locate a serial port

PS C:\Users\ingwi\Work\esp32-test> tinygo flash -x -target=esp32-coreboard-v2 ./main.go
# command-line-arguments
main.go:10:30: undefined: machine.Interrupt
main.go:18:23: undefined: machine.NewInterrupt
main.go:18:52: undefined: machine.PinFalling

(Those are different errors now that are probably on me, so that's much better. ^^)

Thanks for the help!