microbit: WIP on getting Microbit to work with TinyGo

Signed-off-by: Ron Evans <ron@hybridgroup.com>

Makefile

@@ -15,6 +15,11 @@ else ifeq ($(TARGET),pca10040)
 OBJCOPY = arm-none-eabi-objcopy
 TGOFLAGS += -target $(TARGET)
 
+else ifeq ($(TARGET),microbit)
+# BBC:Microbit: nRF51 board
+OBJCOPY = arm-none-eabi-objcopy
+TGOFLAGS += -target $(TARGET)
+
 else ifeq ($(TARGET),bluepill)
 # "blue pill" development board
 # See: https://wiki.stm32duino.com/index.php?title=Blue_Pill
@@ -41,7 +46,10 @@ run-blinky2: build/blinky2
 
 ifeq ($(TARGET),pca10040)
 flash-%: build/%.hex
-	nrfjprog -f nrf52 --sectorerase --program $< --reset
+	/home/ron/bin/nrfjprog/nrfjprog -f nrf52 --sectorerase --program $< --reset
+else ifeq ($(TARGET),microbit)
+flash-%: build/%.hex
+	/home/ron/bin/nrfjprog/nrfjprog -f nrf51 --sectorerase --program $< --reset
 else ifeq ($(TARGET),arduino)
 flash-%: build/%.hex
 	avrdude -c arduino -p atmega328p -P /dev/ttyACM0 -U flash:w:$<

src/machine/board_microbit.go

@@ -0,0 +1,40 @@
+// +build nrf,microbit
+
+package machine
+
+import "device/nrf"
+
+// LEDs on the BBC:Microbit (nRF51 dev board)
+const (
+	LED  = LED1
+	LED1 = 1
+)
+
+// Buttons on the BBC:Microbit (nRF51 dev board)
+const (
+	BUTTON  = BUTTON1
+	BUTTON1 = 5
+	BUTTON2 = 11
+)
+
+func SetLEDS(on bool) {
+	nrf.GPIO.DIRSET = nrf.RegValue(0xfff0)
+	// v = 0                       // All pins to GND so no LED lid
+	// | MASK_LED_ROW_0
+	// | MASK_LED_ROW_1
+	// | MASK_LED_ROW_2
+	// | MASK_LED_COL_0
+	// | MASK_LED_COL_1
+	// | MASK_LED_COL_2
+	// | MASK_LED_COL_3
+	// | MASK_LED_COL_4
+	// | MASK_LED_COL_5
+	// | MASK_LED_COL_6
+	// | MASK_LED_COL_7
+	// | MASK_LED_COL_8
+	if on {
+		nrf.GPIO.OUTSET = nrf.RegValue(0xfff0)
+	} else {
+		nrf.GPIO.OUTCLR = nrf.RegValue(0xfff0)
+	}
+}

src/machine/machine_nrf.go

@@ -18,20 +18,20 @@ const (
 // Configure this pin with the given configuration.
 func (p GPIO) Configure(config GPIOConfig) {
 	cfg := config.Mode | nrf.GPIO_PIN_CNF_DRIVE_S0S1 | nrf.GPIO_PIN_CNF_SENSE_Disabled
-	nrf.P0.PIN_CNF[p.Pin] = nrf.RegValue(cfg)
+	nrf.GPIO.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
+		nrf.GPIO.OUTSET = 1 << p.Pin
 	} else {
-		nrf.P0.OUTCLR = 1 << p.Pin
+		nrf.GPIO.OUTCLR = 1 << p.Pin
 	}
 }
 
 // Get returns the current value of a GPIO pin.
 func (p GPIO) Get() bool {
-	return (nrf.P0.IN>>p.Pin)&1 != 0
+	return (nrf.GPIO.IN>>p.Pin)&1 != 0
 }

src/runtime/runtime_nrf.go

@@ -28,9 +28,10 @@ func init() {
 
 func initUART() {
 	nrf.UART0.ENABLE = nrf.UART_ENABLE_ENABLE_Enabled
-	nrf.UART0.BAUDRATE = nrf.UART_BAUDRATE_BAUDRATE_Baud115200
+	nrf.UART0.BAUDRATE = nrf.UART_BAUDRATE_BAUDRATE_Baud9600
 	nrf.UART0.TASKS_STARTTX = 1
-	nrf.UART0.PSELTXD = 6 // pin 6 for NRF52840-DK
+	nrf.UART0.PSELTXD = 24 // pin 6 for NRF52840-DK
+	nrf.UART0.PSELRXD = 25 // pin 6 for NRF52840-DK
 }
 
 func initLFCLK() {
@@ -48,10 +49,10 @@ func initRTC() {
 }
 
 func putchar(c byte) {
+	nrf.UART0.EVENTS_TXDRDY = 0
 	nrf.UART0.TXD = nrf.RegValue(c)
 	for nrf.UART0.EVENTS_TXDRDY == 0 {
 	}
-	nrf.UART0.EVENTS_TXDRDY = 0
 }
 
 func sleepTicks(d timeUnit) {

targets/microbit.json

@@ -0,0 +1,8 @@
+{
+	"llvm-target": "armv7em-none-eabi",
+	"build-tags": ["microbit", "nrf51", "nrf", "arm", "js", "wasm"],
+	"linker": "arm-none-eabi-gcc",
+	"pre-link-args": ["-nostdlib", "-nostartfiles", "-mcpu=cortex-m4", "-mthumb", "-T", "targets/nrf51.ld", "-Wl,--gc-sections", "-fno-exceptions", "-fno-unwind-tables", "-ffunction-sections", "-fdata-sections", "-Os", "-DNRF51", "-DS110", "-DNRF51_S110", "-Ilib/CMSIS/CMSIS/Include", "lib/nrfx/mdk/system_nrf51.c", "src/device/nrf/nrf51.s"],
+	"objcopy": "arm-none-eabi-objcopy",
+	"flash": "nrfjprog -f nrf51 --sectorerase --program {hex} --reset"
+}

targets/nrf51.ld

@@ -0,0 +1,10 @@
+
+MEMORY
+{
+    FLASH_TEXT (rw) : ORIGIN = 0x00000000, LENGTH = 256K /* .text */
+    RAM (xrw)       : ORIGIN = 0x20000000, LENGTH = 64K
+}
+
+_stack_size = 2K;
+
+INCLUDE "targets/arm.ld"