machine: Rewrite most of the GPIO functionality

Split across device types (nrf, dummy) and use registers directly
instead of the HAL.

src/machine/machine.go

@@ -1,26 +1,18 @@
 
 package machine
 
-// #include "../runtime/runtime_nrf.h"
-import "C"
+type GPIOConfig struct {
+	Mode GPIOMode
+}
 
 type GPIO struct {
-	Pin uint32
+	Pin uint8
 }
 
-type GPIOConfig struct {
-	Mode uint8
+func (p GPIO) High() {
+	p.Set(true)
 }
 
-const (
-	GPIO_INPUT  = iota
-	GPIO_OUTPUT
-)
-
-func (p GPIO) Configure(config GPIOConfig) {
-	C.gpio_cfg(C.uint(p.Pin), C.gpio_mode_t(config.Mode))
-}
-
-func (p GPIO) Set(value bool) {
-	C.gpio_set(C.uint(p.Pin), C.bool(value))
+func (p GPIO) Low() {
+	p.Set(false)
 }

src/machine/machine_dummy.go

@@ -0,0 +1,21 @@
+
+// +build !avr,!nrf
+
+package machine
+
+// Dummy machine package, filled with no-ops.
+
+type GPIOMode uint8
+
+const (
+	GPIO_INPUT  = iota
+	GPIO_OUTPUT
+)
+
+const LED = 0
+
+func (p GPIO) Configure(config GPIOConfig) {
+}
+
+func (p GPIO) Set(value bool) {
+}

src/machine/machine_nrf.go

@@ -0,0 +1,48 @@
+
+// +build nrf
+
+package machine
+
+// #include "../runtime/runtime_nrf.h"
+import "C"
+
+import (
+	"device/nrf"
+)
+
+type GPIOMode uint8
+
+const (
+	GPIO_INPUT  = nrf.P0_PIN_CNF_DIR_Input
+	GPIO_OUTPUT = nrf.P0_PIN_CNF_DIR_Output
+)
+
+// LEDs on the PCA10040 (nRF52832 dev board)
+const (
+	LED  = LED1
+	LED1 = 17
+	LED2 = 18
+	LED3 = 19
+	LED4 = 20
+)
+
+func (p GPIO) Configure(config GPIOConfig) {
+	//C.gpio_cfg(C.uint(p.Pin), C.gpio_mode_t(config.Mode))
+	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
+	}
+	nrf.P0.PIN_CNF[p.Pin] = nrf.RegValue(cfg)
+}
+
+func (p GPIO) Set(high bool) {
+	//C.gpio_set(C.uint(p.Pin), C.bool(value))
+	// TODO: compiler limitation: both operands must be the same LLVM type
+	if high {
+		nrf.P0.OUTSET = 1 << uint32(p.Pin)
+	} else {
+		nrf.P0.OUTCLR = 1 << uint32(p.Pin)
+	}
+}