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https://github.com/tinygo-org/drivers.git
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sago35
113 lines
3.1 KiB
Go
113 lines
3.1 KiB
Go
// Package dht20 implements a driver for the DHT20 temperature and humidity sensor.
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//
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// Datasheet: https://cdn-shop.adafruit.com/product-files/5183/5193_DHT20.pdf
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package dht20
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import (
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"errors"
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"time"
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"tinygo.org/x/drivers"
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)
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var (
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errUpdateCalledTooSoon = errors.New("Update() called within 80ms is invalid")
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)
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// Device wraps an I2C connection to a DHT20 device.
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type Device struct {
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bus drivers.I2C
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Address uint16
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data [8]uint8
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temperature float32
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humidity float32
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prevAccessTime time.Time
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}
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// New creates a new DHT20 connection. The I2C bus must already be
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// configured.
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//
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// This function only creates the Device object, it does not touch the device.
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func New(bus drivers.I2C) Device {
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return Device{
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bus: bus,
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Address: defaultAddress, // Using the address defined in registers.go
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}
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}
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// Configure sets up the device for communication and initializes the registers if needed.
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func (d *Device) Configure() {
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// Get the status word
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d.data[0] = 0x71
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d.bus.Tx(d.Address, d.data[:1], d.data[:1])
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if d.data[0] != 0x18 {
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// Initialize registers
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d.initRegisters()
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}
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// Set the previous access time to the current time
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d.prevAccessTime = time.Now()
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}
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// initRegisters initializes the registers 0x1B, 0x1C, and 0x1E to 0x00.
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func (d *Device) initRegisters() {
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// Initialize register 0x1B
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d.data[0] = 0x1B
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d.data[1] = 0x00
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d.bus.Tx(d.Address, d.data[:2], nil)
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// Initialize register 0x1C
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d.data[0] = 0x1C
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d.data[1] = 0x00
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d.bus.Tx(d.Address, d.data[:2], nil)
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// Initialize register 0x1E
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d.data[0] = 0x1E
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d.data[1] = 0x00
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d.bus.Tx(d.Address, d.data[:2], nil)
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}
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// Update reads data from the sensor and updates the temperature and humidity values.
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// Note that the values obtained by this function are from the previous call to Update.
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// If you want to use the most recent values, shorten the interval at which Update is called.
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func (d *Device) Update(which drivers.Measurement) error {
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// Check if 80ms have passed since the last access
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if time.Since(d.prevAccessTime) < 80*time.Millisecond {
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return errUpdateCalledTooSoon
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}
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// Check the status word Bit[7]
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d.data[0] = 0x71
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d.bus.Tx(d.Address, d.data[:1], d.data[:1])
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if (d.data[0] & 0x80) == 0 {
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// Read 7 bytes of data from the sensor
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d.bus.Tx(d.Address, nil, d.data[:7])
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rawHumidity := uint32(d.data[1])<<12 | uint32(d.data[2])<<4 | uint32(d.data[3])>>4
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rawTemperature := uint32(d.data[3]&0x0F)<<16 | uint32(d.data[4])<<8 | uint32(d.data[5])
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// Convert raw values to human-readable values
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d.humidity = float32(rawHumidity) / 1048576.0 * 100
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d.temperature = float32(rawTemperature)/1048576.0*200 - 50
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// Trigger the next measurement
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d.data[0] = 0xAC
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d.data[1] = 0x33
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d.data[2] = 0x00
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d.bus.Tx(d.Address, d.data[:3], nil)
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// Update the previous access time to the current time
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d.prevAccessTime = time.Now()
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}
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return nil
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}
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// Temperature returns the last measured temperature.
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func (d *Device) Temperature() float32 {
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return d.temperature
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}
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// Humidity returns the last measured humidity.
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func (d *Device) Humidity() float32 {
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return d.humidity
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}
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