TinyGo / WioTerminal - Strange behaviour reading Accelerometer in goroutine

fail.go

package main

import (
	"fmt"
	"image/color"
	"machine"
	"time"

	"tinygo.org/x/drivers/ili9341"
	"tinygo.org/x/drivers/lis3dh"
	"tinygo.org/x/tinyfont"
	"tinygo.org/x/tinyfont/proggy"
)

var (
	display = ili9341.NewSPI(
		machine.SPI3,
		machine.LCD_DC,
		machine.LCD_SS_PIN,
		machine.LCD_RESET,
	)

	backlight = machine.LCD_BACKLIGHT

	Black = color.RGBA{0, 0, 0, 255}
	White = color.RGBA{255, 255, 255, 255}
	Red   = color.RGBA{255, 0, 0, 255}
	Blue  = color.RGBA{0, 0, 255, 255}
	Green = color.RGBA{0, 255, 0, 255}
)

//
// Display
//

func InitDisplay() (width, height int16) {
	machine.SPI3.Configure(machine.SPIConfig{
		SCK:       machine.LCD_SCK_PIN,
		SDO:       machine.LCD_SDO_PIN,
		SDI:       machine.LCD_SDI_PIN,
		Frequency: 40000000,
	})

	display.Configure(ili9341.Config{})
	display.SetRotation(ili9341.Rotation270)
	display.FillScreen(color.RGBA{0, 0, 0, 255})

	backlight.Configure(machine.PinConfig{machine.PinOutput})
	backlight.High()

	return display.Size()
}

func Status(msg string, fg color.RGBA, bg color.RGBA) {
	display.FillRectangle(0, 0, 320, 16, bg)
	tinyfont.WriteLine(display, &proggy.TinySZ8pt7b, 10, 10, msg, fg)
}

//
// Accelerometer
//

type Accel struct {
	device lis3dh.Device
}

type AccelData struct {
	X, Y, Z int32
}

func NewAccel(i2c machine.I2C, scl, sda machine.Pin) Accel {
	i2c.Configure(machine.I2CConfig{SCL: scl, SDA: sda})
	acc := Accel{device: lis3dh.New(i2c)}
	acc.device.Configure()
	return acc
}

func (a Accel) GetAccel() AccelData {
	x, y, z, _ := a.device.ReadAcceleration()
	return AccelData{X: x, Y: y, Z: z}
}

//
// Main loop
//

func main() {

	InitDisplay()
	acc := NewAccel(machine.I2C0, machine.PIN_WIRE1_SCL, machine.PIN_WIRE1_SDA)
	c := make(chan AccelData)
	go func() {
		for {
			a := acc.GetAccel()
			// XXX Goroutine returns valid accel data if I include debug println
			// XXX but fixed data if I dont (also doesnt work with simple chan
			// XXX recv or range)
			// XXX ????
			println(fmt.Sprintf(">> x: %-8d y: %-8d z: %-8d", a.X, a.Y, a.Z))
			c <- a
			time.Sleep(time.Millisecond * 100)
		}
	}()

	for {
		select {
		case a := <-c:
			s := fmt.Sprintf(">> x: %-8d y: %-8d z: %-8d", a.X, a.Y, a.Z)
			Status(s, White, Red)
		}
	}
}