DHTXX driver (#235)

dhtXX: add new driver for dht thermometer

dht/util.go

@@ -0,0 +1,34 @@
+package dht // import "tinygo.org/x/drivers/dht"
+
+import (
+	"machine"
+	"time"
+)
+
+// Check if the pin is disabled
+func powerUp(p machine.Pin) bool {
+	state := p.Get()
+	if !state {
+		p.High()
+		time.Sleep(startTimeout)
+	}
+	return state
+}
+
+func expectChange(p machine.Pin, oldState bool) counter {
+	cnt := counter(0)
+	for ; p.Get() == oldState && cnt != timeout; cnt++ {
+	}
+	return cnt
+}
+
+func checksum(buf []uint8) uint8 {
+	return buf[4]
+}
+func computeChecksum(buf []uint8) uint8 {
+	return buf[0] + buf[1] + buf[2] + buf[3]
+}
+
+func isValid(buf []uint8) bool {
+	return checksum(buf) == computeChecksum(buf)
+}