aht20: add device

Author: kenbell

Makefile

@@ -187,6 +187,8 @@ endif
 	@md5sum ./build/test.hex
 	tinygo build -size short -o ./build/test.hex -target=feather-m0 ./examples/ina260/main.go
 	@md5sum ./build/test.hex
+	tinygo build -size short -o ./build/test.hex -target=nucleo-l432kc ./examples/aht20/main.go
+	@md5sum ./build/test.hex
 
 DRIVERS = $(wildcard */)
 NOTESTS = build examples flash semihosting pcd8544 shiftregister st7789 microphone mcp3008 gps microbitmatrix \

README.md

@@ -58,6 +58,7 @@ The following 62 devices are supported.
 |----------|-------------|
 | [ADT7410 I2C Temperature Sensor](https://www.analog.com/media/en/technical-documentation/data-sheets/ADT7410.pdf) | I2C |
 | [ADXL345 accelerometer](http://www.analog.com/media/en/technical-documentation/data-sheets/ADXL345.pdf) | I2C |
+| [AHT20 I2C Temperature and Humidity Sensor](http://www.aosong.com/userfiles/files/media/AHT20%20%E8%8B%B1%E6%96%87%E7%89%88%E8%AF%B4%E6%98%8E%E4%B9%A6%20A0%2020201222.pdf) | I2C |
 | [AMG88xx 8x8 Thermal camera sensor](https://cdn-learn.adafruit.com/assets/assets/000/043/261/original/Grid-EYE_SPECIFICATIONS%28Reference%29.pdf) | I2C |
 | [APA102 RGB LED](https://cdn-shop.adafruit.com/product-files/2343/APA102C.pdf) | SPI |
 | [AT24CX 2-wire serial EEPROM](https://www.openimpulse.com/blog/wp-content/uploads/wpsc/downloadables/24C32-Datasheet.pdf) | I2C |

aht20/aht20.go

@@ -0,0 +1,108 @@
+package aht20
+
+import (
+	"time"
+
+	"tinygo.org/x/drivers"
+)
+
+// Device wraps an I2C connection to an AHT20 device.
+type Device struct {
+	bus      drivers.I2C
+	Address  uint16
+	humidity uint32
+	temp     uint32
+}
+
+// New creates a new AHT20 connection. The I2C bus must already be
+// configured.
+//
+// This function only creates the Device object, it does not touch the device.
+func New(bus drivers.I2C) Device {
+	return Device{
+		bus:     bus,
+		Address: Address,
+	}
+}
+
+// Configure the device
+func (d *Device) Configure() {
+	// Check initialization state
+	status := d.Status()
+	if status&0x08 == 1 {
+		// Device is initialized
+		return
+	}
+
+	// Force initialization
+	d.bus.Tx(d.Address, []byte{CMD_INITIALIZE, 0x08, 0x00}, nil)
+	time.Sleep(10 * time.Millisecond)
+}
+
+// Reset the device
+func (d *Device) Reset() {
+	d.bus.Tx(d.Address, []byte{CMD_SOFTRESET}, nil)
+}
+
+// Status of the device
+func (d *Device) Status() byte {
+	data := []byte{0}
+
+	d.bus.Tx(d.Address, []byte{CMD_STATUS}, data)
+
+	return data[0]
+}
+
+// Read the temperature and humidity
+//
+// The actual temperature and humidity are stored
+// and can be accessed using `Temp` and `Humidity`.
+func (d *Device) Read() error {
+	d.bus.Tx(d.Address, []byte{CMD_TRIGGER, 0x33, 0x00}, nil)
+
+	data := []byte{0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}
+	for retry := 0; retry < 3; retry++ {
+		time.Sleep(80 * time.Millisecond)
+		err := d.bus.Tx(d.Address, nil, data)
+		if err != nil {
+			return err
+		}
+
+		// If measurement complete, store values
+		if data[0]&0x04 != 0 && data[0]&0x80 == 0 {
+			d.humidity = uint32(data[1])<<12 | uint32(data[2])<<4 | uint32(data[3])>>4
+			d.temp = (uint32(data[3])&0xF)<<16 | uint32(data[4])<<8 | uint32(data[5])
+			return nil
+		}
+	}
+
+	return ErrTimeout
+}
+
+func (d *Device) RawHumidity() uint32 {
+	return d.humidity
+}
+
+func (d *Device) RawTemp() uint32 {
+	return d.temp
+}
+
+func (d *Device) RelHumidity() float32 {
+	return (float32(d.humidity) * 100) / 0x100000
+}
+
+func (d *Device) DeciRelHumidity() int32 {
+	return (int32(d.humidity) * 1000) / 0x100000
+}
+
+// Temperature in degrees celsius
+func (d *Device) Celsius() float32 {
+	return (float32(d.temp*200.0) / 0x100000) - 50
+}
+
+// Temperature in mutiples of one tenth of a degree celsius
+//
+// Using this method avoids floating point calculations.
+func (d *Device) DeciCelsius() int32 {
+	return ((int32(d.temp) * 2000) / 0x100000) - 500
+}

aht20/aht20_test.go

@@ -0,0 +1,74 @@
+package aht20
+
+import (
+	"testing"
+
+	qt "github.com/frankban/quicktest"
+	"tinygo.org/x/drivers/tester"
+)
+
+func TestDefaultI2CAddress(t *testing.T) {
+	c := qt.New(t)
+	bus := tester.NewI2CBus(c)
+	dev := New(bus)
+	c.Assert(uint8(dev.Address), qt.Equals, uint8(Address))
+}
+
+func TestInitialization(t *testing.T) {
+	c := qt.New(t)
+	bus := tester.NewI2CBus(c)
+	fdev := tester.NewI2CDeviceCmd(c, Address)
+	fdev.Commands = defaultCommands()
+	bus.AddDevice(fdev)
+
+	// Set status to uninitialized to force initialization
+	fdev.Commands[CMD_STATUS].Response[0] = 0x0C
+
+	dev := New(bus)
+	dev.Configure()
+
+	// Check initialization command invoked
+	c.Assert(fdev.Commands[CMD_INITIALIZE].Invocations > 0, qt.Equals, true)
+}
+
+func TestRead(t *testing.T) {
+	c := qt.New(t)
+	bus := tester.NewI2CBus(c)
+	fdev := tester.NewI2CDeviceCmd(c, Address)
+	fdev.Commands = defaultCommands()
+	bus.AddDevice(fdev)
+
+	dev := New(bus)
+	dev.Read()
+
+	// Should be 25deg (250 decidegrees)
+	c.Assert(dev.DeciCelsius(), qt.Equals, int32(250))
+
+	// Should be 36.3% (363 decipercent)
+	c.Assert(dev.DeciRelHumidity(), qt.Equals, int32(363))
+}
+
+func defaultCommands() map[uint8]*tester.Cmd {
+	return map[uint8]*tester.Cmd{
+		CMD_INITIALIZE: {
+			Command:  []byte{0xBE},
+			Mask:     []byte{0xFF},
+			Response: []byte{},
+		},
+		CMD_TRIGGER: {
+			Command:  []byte{0xAC, 0x33, 0x00},
+			Mask:     []byte{0xFF, 0xFF, 0xFF},
+			Response: []byte{0x1C, 0x5D, 0x10, 0x66, 0x01, 0xD2, 0x93},
+		},
+		CMD_SOFTRESET: {
+			Command:  []byte{0xBA},
+			Mask:     []byte{0xFF},
+			Response: []byte{},
+		},
+		CMD_STATUS: {
+			Command:  []byte{0x71},
+			Mask:     []byte{0xFF},
+			Response: []byte{0x1C},
+		},
+	}
+}

aht20/registers.go

@@ -0,0 +1,20 @@
+package aht20
+
+import "errors"
+
+const (
+	Address = 0x38
+
+	CMD_INITIALIZE = 0xBE
+	CMD_STATUS     = 0x71
+	CMD_TRIGGER    = 0xAC
+	CMD_SOFTRESET  = 0xBA
+
+	STATUS_BUSY       = 0x80
+	STATUS_CALIBRATED = 0x08
+)
+
+var (
+	ErrBusy    = errors.New("device busy")
+	ErrTimeout = errors.New("timeout")
+)

examples/aht20/main.go

@@ -0,0 +1,55 @@
+package main
+
+import (
+	"machine"
+	"time"
+
+	"tinygo.org/x/drivers/aht20"
+)
+
+func main() {
+	machine.I2C0.Configure(machine.I2CConfig{})
+
+	dev := aht20.New(machine.I2C0)
+	dev.Configure()
+
+	dev.Reset()
+	for {
+		time.Sleep(500 * time.Millisecond)
+
+		err := dev.Read()
+		if err != nil {
+			println("Error", err)
+			continue
+		}
+
+		println("temp    ", fmtD(dev.DeciCelsius(), 3, 1), "C")
+		println("humidity", fmtD(dev.DeciRelHumidity(), 3, 1), "%")
+	}
+}
+
+func fmtD(val int32, i int, f int) string {
+	result := make([]byte, i+f+1)
+	neg := false
+
+	if val < 0 {
+		val = -val
+		neg = true
+	}
+
+	for p := len(result) - 1; p >= 0; p-- {
+		result[p] = byte(int32('0') + (val % 10))
+		val = val / 10
+
+		if p == i+1 && p > 0 {
+			p--
+			result[p] = '.'
+		}
+	}
+
+	if neg {
+		result[0] = '-'
+	}
+
+	return string(result)
+}