mirror of
https://github.com/tinygo-org/drivers.git
synced 2026-07-26 10:38:41 +00:00
Daniel Esteban
90 lines
2.3 KiB
Go
90 lines
2.3 KiB
Go
// Package ds18b20 provides a driver for the DS18B20 digital thermometer
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//
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// Datasheet:
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// https://www.analog.com/media/en/technical-documentation/data-sheets/DS18B20.pdf
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package ds18b20 // import "tinygo.org/x/drivers/ds18b20"
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import (
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"errors"
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)
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// Device ROM commands
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const (
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CONVERT_TEMPERATURE uint8 = 0x44
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READ_SCRATCHPAD uint8 = 0xBE
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WRITE_SCRATCHPAD uint8 = 0x4E
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)
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type OneWireDevice interface {
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Write(uint8)
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Read() uint8
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Select([]uint8) error
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Сrc8([]uint8, int) uint8
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}
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// Device wraps a connection to an 1-Wire devices.
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type Device struct {
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owd OneWireDevice
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}
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// Errors list
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var (
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errReadTemperature = errors.New("Error: DS18B20. Read temperature error: CRC mismatch.")
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)
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func New(owd OneWireDevice) Device {
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return Device{
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owd: owd,
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}
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}
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// Configure. Initializes the device, left for compatibility reasons.
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func (d Device) Configure() {}
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// ThermometerResolution sets thermometer resolution from 9 to 12 bits
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func (d Device) ThermometerResolution(romid []uint8, resolution uint8) {
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if 9 <= resolution && resolution <= 12 {
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d.owd.Select(romid)
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d.owd.Write(WRITE_SCRATCHPAD) // send three data bytes to scratchpad (TH, TL, and config)
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d.owd.Write(0xFF) // to TH
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d.owd.Write(0x00) // to TL
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d.owd.Write(((resolution - 9) << 5) | 0x1F) // to resolution config
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}
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}
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// RequestTemperature sends request to device
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func (d Device) RequestTemperature(romid []uint8) {
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d.owd.Select(romid)
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d.owd.Write(CONVERT_TEMPERATURE)
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}
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// ReadTemperatureRaw returns the raw temperature.
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// ScratchPad memory map:
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// byte 0: Temperature LSB
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// byte 1: Temperature MSB
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func (d Device) ReadTemperatureRaw(romid []uint8) ([]uint8, error) {
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spb := make([]uint8, 9) // ScratchPad buffer
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d.owd.Select(romid)
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d.owd.Write(READ_SCRATCHPAD)
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for i := 0; i < 9; i++ {
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spb[i] = d.owd.Read()
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}
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if d.owd.Сrc8(spb, 8) != spb[8] {
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return nil, errReadTemperature
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}
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return spb[:2:2], nil
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}
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// ReadTemperature returns the temperature in celsius milli degrees (°C/1000)
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func (d Device) ReadTemperature(romid []uint8) (int32, error) {
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raw, err := d.ReadTemperatureRaw(romid)
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if err != nil {
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return 0, err
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}
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t := int32(uint16(raw[0]) | uint16(raw[1])<<8)
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if t&0x8000 == 0x8000 {
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t -= 0x10000
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}
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return (t * 625 / 10), nil
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}
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