Add support for LPS22HB MEMS nano pressure sensor (#297)

lps22hb: add support for lps22hb

lps22hb/lps22hb.go

@@ -0,0 +1,73 @@
+// Package lps22hb implements a driver for LPS22HB, a MEMS nano pressure sensor.
+//
+// Datasheet: https://www.st.com/resource/en/datasheet/dm00140895.pdf
+//
+package lps22hb
+
+import (
+	"tinygo.org/x/drivers"
+)
+
+// Device wraps an I2C connection to a HTS221 device.
+type Device struct {
+	bus     drivers.I2C
+	Address uint8
+}
+
+// Connected returns whether LPS22HB has been found.
+// It does a "who am I" request and checks the response.
+func (d *Device) Connected() bool {
+	data := []byte{0}
+	d.bus.ReadRegister(d.Address, LPS22HB_WHO_AM_I_REG, data)
+	return data[0] == 0xB1
+}
+
+// Configure sets up the LPS22HB device for communication.
+func (d *Device) Configure() {
+	// set to block update mode
+	d.bus.WriteRegister(d.Address, LPS22HB_CTRL1_REG, []byte{0x02})
+}
+
+// ReadPressure returns the pressure in milli pascals (mPa).
+func (d *Device) ReadPressure() (pressure int32, err error) {
+	d.waitForOneShot()
+
+	// read data
+	data := []byte{0, 0, 0}
+	d.bus.ReadRegister(d.Address, LPS22HB_PRESS_OUT_REG, data[:1])
+	d.bus.ReadRegister(d.Address, LPS22HB_PRESS_OUT_REG+1, data[1:2])
+	d.bus.ReadRegister(d.Address, LPS22HB_PRESS_OUT_REG+2, data[2:])
+	pValue := float32(uint32(data[2])<<16|uint32(data[1])<<8|uint32(data[0])) / 4096.0
+
+	return int32(pValue * 1000), nil
+}
+
+// ReadTemperature returns the temperature in celsius milli degrees (°C/1000).
+func (d *Device) ReadTemperature() (temperature int32, err error) {
+	d.waitForOneShot()
+
+	// read data
+	data := []byte{0, 0}
+	d.bus.ReadRegister(d.Address, LPS22HB_TEMP_OUT_REG, data[:1])
+	d.bus.ReadRegister(d.Address, LPS22HB_TEMP_OUT_REG+1, data[1:])
+	tValue := float32(int16(uint16(data[1])<<8|uint16(data[0]))) / 100.0
+
+	return int32(tValue * 1000), nil
+}
+
+// private functions
+
+// wait and trigger one shot in block update
+func (d *Device) waitForOneShot() {
+	// trigger one shot
+	d.bus.WriteRegister(d.Address, LPS22HB_CTRL2_REG, []byte{0x01})
+
+	// wait until one shot is cleared
+	data := []byte{1}
+	for {
+		d.bus.ReadRegister(d.Address, LPS22HB_CTRL2_REG, data)
+		if data[0]&0x01 == 0 {
+			break
+		}
+	}
+}