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pleomaxx3002
117 lines
3.1 KiB
Go
117 lines
3.1 KiB
Go
// Package dht provides a driver for DHTXX family temperature and humidity sensors.
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//
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// [1] Datasheet DHT11: https://www.mouser.com/datasheet/2/758/DHT11-Technical-Data-Sheet-Translated-Version-1143054.pdf
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// [2] Datasheet DHT22: https://cdn-shop.adafruit.com/datasheets/Digital+humidity+and+temperature+sensor+AM2302.pdf
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// Adafruit C++ driver: https://github.com/adafruit/DHT-sensor-library
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package dht // import "tinygo.org/x/drivers/dht"
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import (
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"encoding/binary"
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"machine"
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"time"
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)
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// enum type for device type
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type DeviceType uint8
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// DeviceType specific parsing of information received from the sensor
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func (d DeviceType) extractData(buf []byte) (temp int16, hum uint16) {
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if d == DHT11 {
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temp = int16(buf[2])
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if buf[3]&0x80 > 0 {
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temp = -1 - temp
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}
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temp *= 10
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temp += int16(buf[3] & 0x0f)
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hum = 10*uint16(buf[0]) + uint16(buf[1])
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} else {
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hum = binary.LittleEndian.Uint16(buf[0:2])
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temp = int16(buf[3])<<8 + int16(buf[2]&0x7f)
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if buf[2]&0x80 > 0 {
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temp = -temp
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}
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}
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return
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}
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// Celsius and Fahrenheit temperature scales
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type TemperatureScale uint8
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func (t TemperatureScale) convertToFloat(temp int16) float32 {
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if t == C {
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return float32(temp) / 10
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} else {
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// Fahrenheit
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return float32(temp)*(9.0/50.) + 32.
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}
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}
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// All functions return ErrorCode instance as error. This class can be used for more efficient error processing
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type ErrorCode uint8
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const (
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startTimeout = time.Millisecond * 200
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startingLow = time.Millisecond * 20
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DHT11 DeviceType = iota
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DHT22
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C TemperatureScale = iota
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F
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ChecksumError ErrorCode = iota
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NoSignalError
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NoDataError
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UpdateError
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UninitializedDataError
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)
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// error interface implementation for ErrorCode
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func (e ErrorCode) Error() string {
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switch e {
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case ChecksumError:
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// DHT returns ChecksumError if all the data from the sensor was received, but the checksum does not match.
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return "checksum mismatch"
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case NoSignalError:
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// DHT returns NoSignalError if there was no reply from the sensor. Check sensor connection or the correct pin
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// sis chosen,
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return "no signal"
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case NoDataError:
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// DHT returns NoDataError if the connection was successfully initialized, but not all 40 bits from
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// the sensor is received
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return "no data"
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case UpdateError:
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// DHT returns UpdateError if ReadMeasurements function is called before time specified in UpdatePolicy or
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// less than 2 seconds after past measurement
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return "cannot update now"
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case UninitializedDataError:
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// DHT returns UninitializedDataError if user attempts to access data before first measurement
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return "no measurements done"
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}
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// should never be reached
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return "unknown error"
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}
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// Update policy of the DHT device. UpdateTime cannot be shorter than 2 seconds. According to dht specification sensor
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// will return undefined data if update requested less than 2 seconds before last usage
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type UpdatePolicy struct {
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UpdateTime time.Duration
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UpdateAutomatically bool
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}
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var (
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// timeout counter equal to number of ticks per 1 millisecond
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timeout counter
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)
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func init() {
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timeout = cyclesPerMillisecond()
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}
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func cyclesPerMillisecond() counter {
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freq := machine.CPUFrequency()
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freq /= 1000
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return counter(freq)
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}
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