CS816 Tinygo

cst816.go

package main

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

	"tinygo.org/x/drivers/st7789"
)

// --- CST816S/D Touch Driver ---

const cst816Address = 0x15

const (
	RegFingerNum     = 0x02
	RegXposH         = 0x03
	RegIrqPluseWidth = 0xED
	RegNorScanPer    = 0xEE
	RegIrqCtl        = 0xFA
	RegDisAutoSleep  = 0xFE
)

type CST816 struct {
	bus *machine.I2C 
	rst machine.Pin
	int machine.Pin
}

func NewCST816(bus *machine.I2C, rst, intPin machine.Pin) *CST816 {
	return &CST816{bus: bus, rst: rst, int: intPin}
}

func (d *CST816) Configure() error {
	d.rst.Configure(machine.PinConfig{Mode: machine.PinOutput})
	d.int.Configure(machine.PinConfig{Mode: machine.PinInputPullup})

	// Hardware Reset
	d.rst.Low()
	time.Sleep(100 * time.Millisecond)
	d.rst.High()
	time.Sleep(100 * time.Millisecond)

	// Wake up / Stop Auto Sleep
	d.bus.Tx(cst816Address, []byte{RegDisAutoSleep, 0x01}, nil)

	// Enable Point Mode (Continuous coordinate reporting)
	d.bus.Tx(cst816Address, []byte{RegIrqCtl, 0x41}, nil)
	d.bus.Tx(cst816Address, []byte{RegIrqPluseWidth, 0x01}, nil)
	d.bus.Tx(cst816Address, []byte{RegNorScanPer, 0x01}, nil)

	return nil
}

// Read returns X, Y coordinates and a boolean indicating if touched.
func (d *CST816) Read() (int16, int16, bool) {
	data := make([]byte, 5)

	// Read starting from FingerNum (0x02) to YposL (0x06)
	err := d.bus.Tx(cst816Address, []byte{RegFingerNum}, data)
	if err != nil || data[0] == 0 {
		return 0, 0, false
	}

	// Cast the byte to int16 *before* shifting left by 8
	rawX := (int16(data[1]&0x0F) << 8) | int16(data[2])
	rawY := (int16(data[3]&0x0F) << 8) | int16(data[4])

	// Match the hardware orientation 
	x := rawY
	y := 240 - rawX

	return x, y, true
}