121 lines
2.6 KiB
Go
121 lines
2.6 KiB
Go
package main
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import (
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"fmt"
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"errors"
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"github.com/warthog618/gpio"
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"math"
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"time"
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)
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const Timeout = math.MaxInt32
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const TimeoutErrInitial string = "timed out waiting for sensor's initial %s reading"
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var oneSecondInCycles = (func() int {
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result := cyclesInAMillisecond()
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for i := 0; i < 100; i++ {
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result += cyclesInAMillisecond()
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}
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fmt.Printf("cycles %v", result)
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return result / 100
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})()
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func cyclesInAMillisecond() int {
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count := 0
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start := time.Now().UnixNano()
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for {
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count++
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if time.Now().UnixNano() - start >= 1000000 {
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break
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}
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}
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return count
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}
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func main() {
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err := gpio.Open()
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if err != nil {
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panic(err)
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}
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defer gpio.Close()
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pin := gpio.NewPin(gpio.GPIO4)
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dhtData, err := readDataFromDHT(pin)
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if err != nil {
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fmt.Println(fmt.Sprintf("Bad read! Reason: %s!", err.Error()))
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} else {
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fmt.Println(convertToRhAndTemp(dhtData))
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}
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}
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func readDataFromDHT(pin *gpio.Pin) ([5]byte, error) {
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// Setup
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pin.PullUp()
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time.Sleep(time.Second)
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// Send start signal
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pin.Low()
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pin.Output()
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time.Sleep(1100 * time.Microsecond)
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pin.Input()
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time.Sleep(30 * time.Microsecond)
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// Wait for high low signal
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cyclesLo := cyclesForReading(pin, gpio.Low)
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if cyclesLo == Timeout {
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return [5]byte{}, errors.New(fmt.Sprintf(TimeoutErrInitial, "low"))
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}
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cyclesHi := cyclesForReading(pin, gpio.High)
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if cyclesHi == Timeout {
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return [5]byte{}, errors.New(fmt.Sprintf(TimeoutErrInitial, "high"))
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}
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pulsesAsCycles := readPulsesAsCycles(pin)
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fmt.Printf("lo %v, hi %v", cyclesLo, cyclesHi)
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receivedInput, err := storeCycleCountsAsBinarySequence(&pulsesAsCycles)
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if err != nil {
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return [5]byte{}, err
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}
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return receivedInput, nil
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}
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func cyclesForReading(pin *gpio.Pin, level gpio.Level) int {
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count := 0
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for pin.Read() == level {
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count++
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if count >= oneSecondInCycles {
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return Timeout
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}
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}
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return count
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}
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func readPulsesAsCycles(pin *gpio.Pin) [80]int {
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cycles := [80]int{}
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for i := 0; i < 80; i += 2 {
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cycles[i] = cyclesForReading(pin, gpio.Low)
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cycles[i + 1] = cyclesForReading(pin, gpio.High)
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}
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return cycles
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}
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func storeCycleCountsAsBinarySequence(cycles *[80]int) ([5]byte, error) {
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data := [5]byte{}
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for i := 0; i < 40; i++ {
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lowCycles := cycles[2 * i]
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highCycles := cycles[2 * i + 1]
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if (lowCycles == Timeout) || (highCycles == Timeout) {
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return [5]byte{}, errors.New("timed out waiting for sensor pulse")
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}
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data[i / 8] <<= 1
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if highCycles > lowCycles {
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data[i / 8] |= 1
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}
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}
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return data, nil
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}
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func convertToRhAndTemp(data [5]byte) (float32, float32) {
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rh := float32(data[0]) + float32(int(data[1]) << 4)
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temp := float32(data[2]) + float32(int(data[3]) << 4)
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return rh/10, temp/10
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}
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