shtc3: Sensirion SHTC3 Relative Humidity / Temperature i2c sensor

Makefile

@@ -117,6 +117,8 @@ smoke-test:
 	@md5sum ./build/test.hex
 	tinygo build -size short -o ./build/test.hex -target=microbit ./examples/sht3x/main.go
 	@md5sum ./build/test.hex
+	tinygo build -size short -o ./build/test.hex -target=microbit ./examples/shtc3/main.go
+	@md5sum ./build/test.hex
 	tinygo build -size short -o ./build/test.hex -target=microbit ./examples/ssd1306/i2c_128x32/main.go
 	@md5sum ./build/test.hex
 	tinygo build -size short -o ./build/test.hex -target=microbit ./examples/ssd1306/spi_128x64/main.go

README.md

@@ -52,7 +52,7 @@ func main() {
 
 ## Currently supported devices
 
-The following 74 devices are supported.
+The following 77 devices are supported.
 
 | Device Name | Interface Type |
 |----------|-------------|
@@ -114,6 +114,7 @@ The following 74 devices are supported.
 | [Shift register (PISO)](https://en.wikipedia.org/wiki/Shift_register#Parallel-in_serial-out_\(PISO\)) | GPIO |
 | [Shift registers (SIPO)](https://en.wikipedia.org/wiki/Shift_register#Serial-in_parallel-out_(SIPO)) | GPIO |
 | [SHT3x Digital Humidity Sensor](https://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/2_Humidity_Sensors/Datasheets/Sensirion_Humidity_Sensors_SHT3x_Datasheet_digital.pdf) | I2C |
+| [SHTC3 Digital Humidity Sensor (RH/T)](https://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/2_Humidity_Sensors/Datasheets/Sensirion_Humidity_Sensors_SHTC3_Datasheet.pdf) | I2C |
 | [SPI NOR Flash Memory](https://en.wikipedia.org/wiki/Flash_memory#NOR_flash) | SPI/QSPI |
 | [SPI SDCARD/MMC](https://en.wikipedia.org/wiki/SD_card) | SPI |
 | [SSD1306 OLED display](https://cdn-shop.adafruit.com/datasheets/SSD1306.pdf) | I2C / SPI |

examples/shtc3/main.go

@@ -0,0 +1,30 @@
+package main
+
+import (
+	"fmt"
+	"machine"
+	"time"
+
+	"tinygo.org/x/drivers/shtc3"
+)
+
+func main() {
+
+	machine.I2C0.Configure(machine.I2CConfig{})
+	sensor := shtc3.New(machine.I2C0)
+
+	for {
+
+		sensor.WakeUp()
+
+		temp, humidity, _ := sensor.ReadTemperatureHumidity()
+		t := fmt.Sprintf("%.2f", float32(temp)/1000)
+		h := fmt.Sprintf("%.2f", float32(humidity)/100)
+		println("Temperature:", t, "°C")
+		println("Humidity", h, "%")
+
+		sensor.Sleep()
+
+		time.Sleep(2 * time.Second)
+	}
+}

shtc3/registers.go

@@ -0,0 +1,11 @@
+package shtc3
+
+// Constants used for I2C.
+
+const (
+	SHTC3_ADDRESS        = 0x70
+	SHTC3_CMD_WAKEUP     = "\x35\x17" // Wake up
+	SHTC3_CMD_MEASURE_HP = "\x7C\xA2" // Read sensor in high power mode with clock stretching
+	SHTC3_CMD_SLEEP      = "\xB0\x98" // Sleep
+	SHTC3_CMD_SOFT_RESET = "\x80\x5D" // Soft Reset
+)

shtc3/shtc3.go

@@ -0,0 +1,79 @@
+// Package shtc3 provides a driver for the SHTC3 digital humidity sensor
+// series by Sensirion.
+//
+// Datasheet:
+// https://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/2_Humidity_Sensors/Datasheets/Sensirion_Humidity_Sensors_SHTC3_Datasheet.pdf
+//
+package shtc3 // import "tinygo.org/x/drivers/shtc3"
+
+import (
+	"time"
+
+	"tinygo.org/x/drivers"
+)
+
+// Device wraps an I2C connection to a SHT31 device.
+type Device struct {
+	bus drivers.I2C
+}
+
+// New creates a new SHTC3 connection. The I2C bus must already be
+// configured.
+//
+// This function only creates the Device object, it does not initialize the device.
+// You must call Configure() first in order to use the device itself.
+func New(bus drivers.I2C) Device {
+	return Device{
+		bus: bus,
+	}
+}
+
+// Read returns the temperature in celsius milli degrees (°C/1000).
+func (d *Device) ReadTemperature() (tempMilliCelsius int32, err error) {
+	tempMilliCelsius, _, err = d.ReadTemperatureHumidity()
+	return tempMilliCelsius, err
+}
+
+// Read returns the relative humidity in hundredths of a percent.
+func (d *Device) ReadHumidity() (relativeHumidity int16, err error) {
+	_, relativeHumidity, err = d.ReadTemperatureHumidity()
+	return relativeHumidity, err
+}
+
+// Read returns both the temperature and relative humidity.
+func (d *Device) ReadTemperatureHumidity() (tempMilliCelsius int32, relativeHumidity int16, err error) {
+	var rawTemp, rawHum, errx = d.rawReadings()
+	if errx != nil {
+		err = errx
+		return
+	}
+	tempMilliCelsius = ((21875 * int32(rawTemp)) >> 13) - 45000
+	relativeHumidity = int16((1250 * int32(rawHum)) >> 13)
+	return tempMilliCelsius, relativeHumidity, err
+}
+
+// rawReadings returns the sensor's raw values of the temperature and humidity
+func (d *Device) rawReadings() (uint16, uint16, error) {
+	var data [6]byte
+	d.bus.Tx(SHTC3_ADDRESS, []byte(SHTC3_CMD_MEASURE_HP), data[:])
+	// ignore crc for now
+	return readUint(data[0], data[1]), readUint(data[3], data[4]), nil
+}
+
+// WakeUp makes device leave sleep mode
+func (d *Device) WakeUp() error {
+	d.bus.Tx(SHTC3_ADDRESS, []byte(SHTC3_CMD_WAKEUP), nil)
+	time.Sleep(1 * time.Millisecond)
+	return nil
+}
+
+// Sleep makes device go to sleep
+func (d *Device) Sleep() error {
+	d.bus.Tx(SHTC3_ADDRESS, []byte(SHTC3_CMD_SLEEP), nil)
+	return nil
+}
+
+// readUint converts two bytes to uint16
+func readUint(msb byte, lsb byte) uint16 {
+	return (uint16(msb) << 8) | uint16(lsb)
+}