seesaw: device support and tests

seesaw/seesaw.go

@@ -0,0 +1,130 @@
+// Package seesaw provides a driver implementation to communicate with Adafruit's seesaw chip.
+// There are many Adafruit boards that use a seesaw. Moisture sensors, LED keyboards, ...
+package seesaw
+
+import (
+	"errors"
+	"strconv"
+	"time"
+	"tinygo.org/x/drivers"
+)
+
+const DefaultAddress = 0x49
+
+// empirically determined standardDelay, the one from the official library seems to be too short (250us)
+const defaultDelay = 100 * time.Millisecond
+
+const (
+	seesawHwIdCodeSAMD09  = 0x55 // HW ID code for SAMD09
+	seesawHwIdCodeTINY8x7 = 0x87 // HW ID code for ATtiny817
+)
+
+type Seesaw interface {
+
+	// Read reads a number of bytes from the device after sending the read command and waiting 'delay'. The delays depend
+	// on the module and function and are documented in the seesaw datasheet
+	Read(module ModuleBaseAddress, function FunctionAddress, buf []byte, delay time.Duration) error
+
+	// Write writes an entire array into a given module and function
+	Write(module ModuleBaseAddress, function FunctionAddress, buf []byte) error
+}
+
+type Device struct {
+	bus           drivers.I2C
+	Address       uint16
+	standardDelay time.Duration
+}
+
+func New(bus drivers.I2C) *Device {
+	return &Device{
+		bus:           bus,
+		Address:       DefaultAddress,
+		standardDelay: defaultDelay,
+	}
+}
+
+// SoftReset triggers a soft-reset of seesaw and waits for it to be ready
+func (d *Device) SoftReset() error {
+	err := d.WriteRegister(ModuleStatusBase, FunctionStatusSwrst, 0xFF)
+	if err != nil {
+		return errors.New("failed sending soft-reset command: " + err.Error())
+	}
+
+	return d.waitForReset()
+}
+
+func (d *Device) waitForReset() error {
+
+	//give the device a little bit of time to reset
+	time.Sleep(time.Second)
+
+	var lastErr error
+	tries := 0
+	for ; tries < 20; tries++ {
+		_, err := d.readHardwareID()
+		if err == nil {
+			return nil
+		}
+		lastErr = err
+		time.Sleep(20 * time.Millisecond)
+	}
+	return errors.New("failed to wait for device to start: " + lastErr.Error())
+}
+
+func (d *Device) readHardwareID() (byte, error) {
+	hwid, err := d.ReadRegister(ModuleStatusBase, FunctionStatusHwId)
+	if err != nil {
+		return 0, err
+	}
+
+	if hwid == seesawHwIdCodeSAMD09 || hwid == seesawHwIdCodeTINY8x7 {
+		return hwid, nil
+	}
+
+	return 0, errors.New("unknown hardware ID: " + strconv.FormatUint(uint64(hwid), 16))
+}
+
+// WriteRegister writes a single seesaw register
+func (d *Device) WriteRegister(module ModuleBaseAddress, function FunctionAddress, value byte) error {
+	var buf [3]byte
+	buf[0] = byte(module)
+	buf[1] = byte(function)
+	buf[2] = value
+	return d.bus.Tx(d.Address, buf[:], nil)
+}
+
+// ReadRegister reads a single register from seesaw
+func (d *Device) ReadRegister(module ModuleBaseAddress, function FunctionAddress) (byte, error) {
+	var buf [1]byte
+	err := d.Read(module, function, buf[:], d.standardDelay)
+	if err != nil {
+		return 0, err
+	}
+	return buf[0], nil
+}
+
+// Read reads a number of bytes from the device after sending the read command and waiting 'standardDelay'. The delays depend
+// on the module and function and are documented in the seesaw datasheet
+func (d *Device) Read(module ModuleBaseAddress, function FunctionAddress, buf []byte, delay time.Duration) error {
+	var cmd [2]byte
+	cmd[0] = byte(module)
+	cmd[1] = byte(function)
+
+	err := d.bus.Tx(d.Address, cmd[:], nil)
+	if err != nil {
+		return err
+	}
+
+	//This is needed for the client seesaw device to flush its RX buffer and process the command.
+	//See seesaw datasheet for timings for specific modules.
+	time.Sleep(delay)
+
+	return d.bus.Tx(d.Address, nil, buf)
+}
+
+// Write writes data into a given module and function
+func (d *Device) Write(module ModuleBaseAddress, function FunctionAddress, buf []byte) error {
+	cmd := []byte{byte(module), byte(function)}
+	data := append(cmd, buf...)
+	return d.bus.Tx(d.Address, data, nil)
+}