Added driver to decode signal from Silvan *1527 OTP encoder chips.

Makefile

@@ -227,13 +227,15 @@ endif
 	@md5sum ./build/test.hex
 	tinygo build -size short -o ./build/test.uf2 -target=pico ./examples/ssd1289/main.go
 	@md5sum ./build/test.uf2
+	tinygo build -size short -o ./build/test.hex -target=arduino-nano33 ./examples/otp1527
+	@md5sum ./build/test.hex
 
 DRIVERS = $(wildcard */)
 NOTESTS = build examples flash semihosting pcd8544 shiftregister st7789 microphone mcp3008 gps microbitmatrix \
 		hcsr04 ssd1331 ws2812 thermistor apa102 easystepper ssd1351 ili9341 wifinina shifter hub75 \
 		hd44780 buzzer ssd1306 espat l9110x st7735 bmi160 l293x dht keypad4x4 max72xx p1am tone tm1637 \
 		pcf8563 mcp2515 servo sdcard rtl8720dn image cmd i2csoft hts221 lps22hb apds9960 axp192 xpt2046 \
-		ft6336 sx126x ssd1289
+		ft6336 sx126x ssd1289 otp1527
 TESTS = $(filter-out $(addsuffix /%,$(NOTESTS)),$(DRIVERS))
 
 unit-test:

examples/otp1527/main.go

@@ -0,0 +1,16 @@
+package main
+
+import (
+	"fmt"
+	"machine"
+
+	"tinygo.org/x/drivers/otp1527"
+)
+
+func main() {
+	d := otp1527.NewDecoder(machine.Pin(3), -1)
+	for {
+		v := <-d.Out()
+		println(fmt.Sprintf("RECV: 0x%06x", v.Data))
+	}
+}

otp1527/otp1527.go

@@ -0,0 +1,120 @@
+// Package otp1527 implements a driver to decode signal transmitted over 433MHz
+// by various key fob, leak detectors, etc., which are based on Silvan OTP
+// Encoder chips HS1527, EV1527, RT1527, or FP1527.
+// See http://sc-tech.cn/en/hs1527.pdf for details.
+// This package works with microcontrollers that support GPIO PinToggle interrupt.
+// Check example under examples/otp1527
+//
+
+package otp1527
+
+import (
+	"machine"
+	"time"
+)
+
+type Value struct {
+	Data   uint32 // Received code
+	Period uint32 // Data clock (preamble time / 31)
+}
+
+type OTP1527 struct {
+	Filter         int   // number of cycles to run signal debouncing (default 65)
+	PreambleClkMin int64 // data preamble minimal length (ns) to limit false positives (default 200000)
+	PreambleClkMax int64 // data preamble maximal length (ns) to limit false positives (default 600000)
+	pin            machine.Pin
+	ch             chan Value
+	time           int64
+	preambleClk    int64
+	timeHigh       int64
+	data           uint32
+	bits           int
+	last           bool
+}
+
+// NewDecoder create driver to decode stream generated by HS1527 compatible source
+// and deliver decoded data into output buffered channel of channelSize size.
+// When channelSize set to -1, the size default to 32.
+func NewDecoder(p machine.Pin, channelSize int) *OTP1527 {
+	if channelSize < 0 {
+		channelSize = 32
+	}
+	d := OTP1527{pin: p, ch: make(chan Value, channelSize), Filter: 65, PreambleClkMin: 200000, PreambleClkMax: 600000}
+	d.pin.Configure(machine.PinConfig{Mode: machine.PinInputPullup})
+	if err := d.pin.SetInterrupt(machine.PinToggle, func(p machine.Pin) {
+		d.interrupt()
+	}); err != nil {
+		println("error:", err.Error())
+	}
+	return &d
+}
+
+// Out return output channel for decoded data.
+func (d *OTP1527) Out() <-chan Value {
+	return d.ch
+}
+
+func (d *OTP1527) interrupt() {
+	now := time.Now().UnixNano()
+	// filter signal
+	highCnt := 0
+	for n := 0; n < d.Filter; n++ {
+		v := d.pin.Get()
+		if v {
+			highCnt++
+		} else {
+			highCnt--
+		}
+	}
+	pin := highCnt > 0
+	// decode
+	if d.last != pin {
+		interval := now - d.time
+		if pin == true {
+			d.timeHigh = interval
+		} else {
+			if d.timeHigh > 0 && (d.preambleClk == 0 || (d.preambleClk > d.PreambleClkMin && d.preambleClk < d.PreambleClkMax)) {
+				switch {
+				case interval/d.timeHigh > 20:
+					// this is end of preamble
+					d.resetData()
+					d.preambleClk = interval / 31
+
+				case (interval+d.timeHigh) < d.preambleClk*5 && interval/d.timeHigh > 0:
+					// this is 0
+					d.data = d.data << 1
+					d.bits++
+					// check for last data
+					if d.bits == 24 {
+						d.ch <- Value{Data: d.data, Period: uint32(d.preambleClk)}
+						d.resetData()
+					}
+
+				case (interval+d.timeHigh) < d.preambleClk*5 && interval/d.timeHigh == 0:
+					// this is 1
+					d.data = d.data<<1 | 1
+					d.bits++
+					// check for last data
+					if d.bits == 24 {
+						d.ch <- Value{Data: d.data, Period: uint32(d.preambleClk)}
+						d.resetData()
+					}
+
+				default:
+					d.resetData()
+				}
+			} else {
+				d.resetData()
+			}
+		}
+		d.time = now
+		d.last = pin
+	}
+}
+
+//go:inline
+func (d *OTP1527) resetData() {
+	d.data = 0
+	d.bits = 0
+	d.preambleClk = 0
+}