machine/nrf: implement reading GPIO pins

src/machine/machine_nrf.go

@@ -9,8 +9,10 @@ import (
 type GPIOMode uint8
 
 const (
-	GPIO_INPUT  = nrf.P0_PIN_CNF_DIR_Input
-	GPIO_OUTPUT = nrf.P0_PIN_CNF_DIR_Output
+	GPIO_INPUT          = (nrf.P0_PIN_CNF_DIR_Input << nrf.P0_PIN_CNF_DIR_Pos) | (nrf.P0_PIN_CNF_INPUT_Connect << nrf.P0_PIN_CNF_INPUT_Pos)
+	GPIO_INPUT_PULLUP   = GPIO_INPUT | (nrf.P0_PIN_CNF_PULL_Pullup << nrf.P0_PIN_CNF_PULL_Pos)
+	GPIO_INPUT_PULLDOWN = GPIO_INPUT | (nrf.P0_PIN_CNF_PULL_Pulldown << nrf.P0_PIN_CNF_PULL_Pos)
+	GPIO_OUTPUT         = (nrf.P0_PIN_CNF_DIR_Output << nrf.P0_PIN_CNF_DIR_Pos) | (nrf.P0_PIN_CNF_INPUT_Disconnect << nrf.P0_PIN_CNF_INPUT_Pos)
 )
 
 // LEDs on the PCA10040 (nRF52832 dev board)
@@ -22,16 +24,23 @@ const (
 	LED4 = 20
 )
 
+// Buttons on the PCA10040 (nRF52832 dev board)
+const (
+	BUTTON  = BUTTON1
+	BUTTON1 = 13
+	BUTTON2 = 14
+	BUTTON3 = 15
+	BUTTON4 = 16
+)
+
+// Configure this pin with the given configuration.
 func (p GPIO) Configure(config GPIOConfig) {
-	cfg := config.Mode | nrf.P0_PIN_CNF_PULL_Disabled | nrf.P0_PIN_CNF_DRIVE_S0S1 | nrf.P0_PIN_CNF_SENSE_Disabled
-	if config.Mode == GPIO_INPUT {
-		cfg |= nrf.P0_PIN_CNF_INPUT_Connect
-	} else {
-		cfg |= nrf.P0_PIN_CNF_INPUT_Disconnect
-	}
+	cfg := config.Mode | nrf.P0_PIN_CNF_DRIVE_S0S1 | nrf.P0_PIN_CNF_SENSE_Disabled
 	nrf.P0.PIN_CNF[p.Pin] = nrf.RegValue(cfg)
 }
 
+// Set the pin to high or low.
+// Warning: only use this on an output pin!
 func (p GPIO) Set(high bool) {
 	if high {
 		nrf.P0.OUTSET = 1 << p.Pin
@@ -42,6 +51,5 @@ func (p GPIO) Set(high bool) {
 
 // Get returns the current value of a GPIO pin.
 func (p GPIO) Get() bool {
-	// TODO: implement
-	return false
+	return (nrf.P0.IN>>p.Pin)&1 != 0
 }