Merge pull request #22 from Drahoslav7/feature/edge-event

Edge detection, closes #21

examples/event/event.go

@@ -0,0 +1,49 @@
+/*
+
+An example of edge event handling by @Drahoslav7, using the go-rpio library
+
+Waits for button to be pressed twice before exit.
+
+Connect a button between pin 22 and some GND pin.
+
+*/
+
+package main
+
+import (
+	"fmt"
+	"os"
+	"time"
+
+	"github.com/stianeikeland/go-rpio"
+)
+
+var (
+	// Use mcu pin 22, corresponds to GPIO 3 on the pi
+	pin = rpio.Pin(22)
+)
+
+func main() {
+	// Open and map memory to access gpio, check for errors
+	if err := rpio.Open(); err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+	// Unmap gpio memory when done
+	defer rpio.Close()
+
+	pin.Input()
+	pin.PullUp()
+	pin.Detect(rpio.FallEdge) // enable falling edge event detection
+
+	fmt.Println("press a button")
+
+	for i := 0; i < 2; {
+		if pin.EdgeDetected() { // check if event occured
+			fmt.Println("button pressed")
+			i++
+		}
+		time.Sleep(time.Second / 2)
+	}
+	pin.Detect(rpio.NoEdge) // disable edge event detection
+}

rpio.go

@@ -6,6 +6,7 @@ Supports simple operations such as:
 	- Pin mode/direction (input/output/clock/pwm)
 	- Pin write (high/low)
 	- Pin read (high/low)
+	- Pin edge detection (no/rise/fall/any)
 	- Pull up/down/off
 And clock/pwm related oparations:
 	- Set Clock frequency
@@ -76,6 +77,7 @@ type Mode uint8
 type Pin uint8
 type State uint8
 type Pull uint8
+type Edge uint8
 
 // Memory offsets for gpio, see the spec for more details
 const (
@@ -121,6 +123,14 @@ const (
 	PullUp
 )
 
+// Edge events
+const (
+	NoEdge Edge = iota
+	RiseEdge
+	FallEdge
+	AnyEdge = RiseEdge | FallEdge
+)
+
 // Arrays for 8 / 32 bit access to memory and a semaphore for write locking
 var (
 	memlock  sync.Mutex
@@ -212,6 +222,16 @@ func (pin Pin) PullOff() {
 	PullMode(pin, PullOff)
 }
 
+// Enable edge event detection on pin
+func (pin Pin) Detect(edge Edge) {
+	DetectEdge(pin, edge)
+}
+
+// Check edge event on pin
+func (pin Pin) EdgeDetected() bool {
+	return EdgeDetected(pin)
+}
+
 // PinMode sets the mode (direction) of a given pin (Input, Output, Clock or Pwm)
 //
 // Clock is possible only for pins 4, 5, 6, 20, 21.
@@ -262,7 +282,6 @@ func PinMode(pin Pin, mode Mode) {
 // WritePin sets a given pin High or Low
 // by setting the clear or set registers respectively
 func WritePin(pin Pin, state State) {
-
 	p := uint8(pin)
 
 	// Clear register, 10 / 11 depending on bank
@@ -278,7 +297,6 @@ func WritePin(pin Pin, state State) {
 	} else {
 		gpioMem[setReg] = 1 << (p & 31)
 	}
-
 }
 
 // Read the state of a pin
@@ -304,6 +322,60 @@ func TogglePin(pin Pin) {
 	}
 }
 
+// Enable edge event detection on pin.
+//
+// Combine with pin.EdgeDetected() to check whether event occured.
+//
+// Note that using this function might conflict with the same functionality of other gpio library.
+//
+// It also clears previously detected event of this pin if any.
+//
+// Note that call with RiseEdge will disable previously set FallEdge detection and vice versa.
+// You have to call with AnyEdge, to enable detection for both edges.
+// To disable previously enabled detection call it with NoEdge.
+func DetectEdge(pin Pin, edge Edge) {
+	p := uint8(pin)
+
+	// Rising edge detect enable register (19/20 depending on bank)
+	// Falling edge detect enable register (22/23 depending on bank)
+	// Event detect status register (16/17)
+	renReg := p/32 + 19
+	fenReg := p/32 + 22
+	edsReg := p/32 + 16
+
+	bit := uint32(1 << (p & 31))
+
+	if edge&RiseEdge > 0 { // set bit
+		gpioMem[renReg] = gpioMem[renReg] | bit
+	} else { // clear bit
+		gpioMem[renReg] = gpioMem[renReg] &^ bit
+	}
+	if edge&FallEdge > 0 { // set bit
+		gpioMem[fenReg] = gpioMem[fenReg] | bit
+	} else { // clear bit
+		gpioMem[fenReg] = gpioMem[fenReg] &^ bit
+	}
+
+	gpioMem[edsReg] = bit // to clear outdated detection
+}
+
+// Check whether edge event occured since last call
+// or since detection was enabled
+//
+// There is no way (yet) to handle interruption caused by edge event, you have to use polling.
+//
+// Event detection has to be enabled first, by pin.Detect(edge)
+func EdgeDetected(pin Pin) bool {
+	p := uint8(pin)
+
+	// Event detect status register (16/17)
+	edsReg := p/32 + 16
+
+	test := gpioMem[edsReg] & (1 << (p & 31))
+	gpioMem[edsReg] = test // set bit to clear it
+	return test != 0
+}
+
 func PullMode(pin Pin, pull Pull) {
 	// Pull up/down/off register has offset 38 / 39, pull is 37
 	pullClkReg := pin/32 + 38
@@ -343,7 +415,7 @@ func PullMode(pin Pin, pull Pull) {
 // changing frequency for one pin will change it also for all pins within a group.
 // The groups are:
 //   gp_clk0: pins 4, 20, 32, 34
-//   gp_clk1: pins 5, 21, 42, 43
+//   gp_clk1: pins 5, 21, 42, 44
 //   gp_clk2: pins 6 and 43
 //   pwm_clk: pins 12, 13, 18, 19, 40, 41, 45
 func SetFreq(pin Pin, freq int) {

rpio_test.go

@@ -0,0 +1,120 @@
+package rpio
+
+import (
+	"os"
+	"testing"
+	"time"
+)
+
+func TestMain(m *testing.M) {
+	println("Note: bcm pins 2 and 3 has to be directly connected")
+	if err := Open(); err != nil {
+		panic(err)
+	}
+	defer Close()
+	os.Exit(m.Run())
+}
+
+func TestEvent(t *testing.T) {
+	src := Pin(3)
+	src.Mode(Output)
+
+	pin := Pin(2)
+	pin.Mode(Input)
+	pin.PullDown()
+
+	t.Run("rising edge", func(t *testing.T) {
+		pin.Detect(RiseEdge)
+		src.Low()
+
+		for i := 0; ; i++ {
+			src.High()
+
+			time.Sleep(time.Second / 10)
+			if pin.EdgeDetected() {
+				t.Log("edge rised")
+			} else {
+				t.Errorf("Rise event should be detected")
+			}
+			if i == 5 {
+				break
+			}
+
+			src.Low()
+		}
+
+		time.Sleep(time.Second / 10)
+		if pin.EdgeDetected() {
+			t.Error("Rise should not be detected, no change since last call")
+		}
+		pin.Detect(NoEdge)
+		src.High()
+		if pin.EdgeDetected() {
+			t.Error("Rise should not be detected, events disabled")
+		}
+
+	})
+
+	t.Run("falling edge", func(t *testing.T) {
+		pin.Detect(FallEdge)
+		src.High()
+
+		for i := 0; ; i++ {
+			src.Low()
+
+			time.Sleep(time.Second / 10)
+			if pin.EdgeDetected() {
+				t.Log("edge fallen")
+			} else {
+				t.Errorf("Fall event should be detected")
+			}
+
+			if i == 5 {
+				break
+			}
+
+			src.High()
+		}
+		time.Sleep(time.Second / 10)
+		if pin.EdgeDetected() {
+			t.Error("Fall should not be detected, no change since last call")
+		}
+		pin.Detect(NoEdge)
+		src.Low()
+		if pin.EdgeDetected() {
+			t.Error("Fall should not be detected, events disabled")
+		}
+	})
+
+	t.Run("both edges", func(t *testing.T) {
+		pin.Detect(AnyEdge)
+		src.Low()
+
+		for i := 0; i < 5; i++ {
+			src.High()
+
+			if pin.EdgeDetected() {
+				t.Log("edge detected")
+			} else {
+				t.Errorf("Rise event shoud be detected")
+			}
+
+			src.Low()
+
+			if pin.EdgeDetected() {
+				t.Log("edge detected")
+			} else {
+				t.Errorf("Fall edge should be detected")
+			}
+		}
+
+		pin.Detect(NoEdge)
+		src.High()
+		src.Low()
+
+		if pin.EdgeDetected() {
+			t.Errorf("No edge should be detected, events disabled")
+		}
+
+	})
+}