Add runtime support for the nRF52

.gitmodules

@@ -0,0 +1,6 @@
+[submodule "lib/nrfx"]
+	path = lib/nrfx
+	url = https://github.com/NordicSemiconductor/nrfx.git
+[submodule "lib/CMSIS"]
+	path = lib/CMSIS
+	url = https://github.com/ARM-software/CMSIS.git

src/runtime/print.go

@@ -1,12 +1,9 @@
 
 package runtime
 
-// #include <stdio.h>
-import "C"
-
 func printstring(s string) {
 	for i := 0; i < len(s); i++ {
-		C.putchar(C.int(s[i]))
+		putchar(s[i])
 	}
 }
 
@@ -17,29 +14,30 @@ func printuint(n uint) {
 	if prevdigits != 0 {
 		printuint(prevdigits)
 	}
-	C.putchar(C.int((n % 10) + '0'))
+	putchar(byte((n % 10) + '0'))
 }
 
 func printint(n int) {
 	// Print integer in signed big-endian base-10 notation, for humans to
 	// read.
 	if n < 0 {
-		C.putchar('-')
+		putchar('-')
 		n = -n
 	}
 	printuint(uint(n))
 }
 
 func printbyte(c uint8) {
-	C.putchar(C.int(c))
+	putchar(c)
 }
 
 func printspace() {
-	C.putchar(' ')
+	putchar(' ')
 }
 
 func printnl() {
-	C.putchar('\n')
+	putchar('\r')
+	putchar('\n')
 }
 
 func printitf(msg interface{}) {

src/runtime/runtime.go

@@ -1,16 +1,13 @@
 
 package runtime
 
-// #include <stdlib.h>
-import "C"
-
 const Compiler = "tgo"
 
 func _panic(message interface{}) {
 	printstring("panic: ")
 	printitf(message)
 	printnl()
-	C.exit(1)
+	abort()
 }
 
 func boundsCheck(outOfRange bool) {
@@ -18,6 +15,6 @@ func boundsCheck(outOfRange bool) {
 		// printstring() here is safe as this function is excluded from bounds
 		// checking.
 		printstring("panic: runtime error: index out of range\n")
-		C.exit(1)
+		abort()
 	}
 }

src/runtime/runtime.h

@@ -9,3 +9,5 @@ typedef struct {
 } string_t;
 
 typedef int32_t intgo_t; // may be 64-bit
+
+int main();

src/runtime/runtime_nrf.c

@@ -0,0 +1,41 @@
+
+#include "hal/nrf_uart.h"
+#include "nrf.h"
+#include "runtime.h"
+
+void uart_init(uint32_t pin_tx) {
+	NRF_UART0->ENABLE        = UART_ENABLE_ENABLE_Enabled;
+	NRF_UART0->BAUDRATE      = UART_BAUDRATE_BAUDRATE_Baud115200;
+	NRF_UART0->TASKS_STARTTX = 1;
+	NRF_UART0->PSELTXD       = 6;
+}
+
+void uart_send(uint8_t c) {
+	NRF_UART0->TXD = c;
+	while (NRF_UART0->EVENTS_TXDRDY != 1) {}
+	NRF_UART0->EVENTS_TXDRDY = 0;
+}
+
+void _start() {
+	uart_init(6); // pin_tx = 6, for NRF52840-DK
+	main();
+}
+
+__attribute__((weak))
+void __aeabi_unwind_cpp_pr0() {
+	// dummy, not actually used
+}
+
+__attribute__((weak))
+void __aeabi_memclr(uint8_t *dest, size_t n) {
+	// TODO: link with compiler-rt for a better implementation.
+	// For now, use a simple memory zeroer.
+	for (size_t i = 0; i < n; i++) {
+		dest[i] = 0;
+	}
+}
+
+__attribute__((weak))
+void __aeabi_memclr4(uint8_t *dest, size_t n) {
+	__aeabi_memclr(dest, n);
+}

src/runtime/runtime_nrf.go

@@ -0,0 +1,23 @@
+
+// +build nrf
+
+package runtime
+
+// #include "runtime_nrf.h"
+import "C"
+
+const Microsecond = 1
+
+func putchar(c byte) {
+	C.uart_send(C.uint8_t(c))
+}
+
+func Sleep(d Duration) {
+	// TODO
+}
+
+func abort() {
+	// TODO: wfi
+	for {
+	}
+}

src/runtime/runtime_nrf.h

@@ -0,0 +1,7 @@
+
+#pragma once
+
+#include <stdint.h>
+
+void uart_init(uint32_t pin_tx);
+void uart_send(uint8_t c);

src/runtime/runtime_unix.go

@@ -0,0 +1,23 @@
+
+// +build linux
+
+package runtime
+
+// #include <stdio.h>
+// #include <stdlib.h>
+// #include <unistd.h>
+import "C"
+
+const Microsecond = 1
+
+func putchar(c byte) {
+	C.putchar(C.int(c))
+}
+
+func Sleep(d Duration) {
+	C.usleep(C.useconds_t(d))
+}
+
+func abort() {
+	C.abort()
+}

src/runtime/time.go

@@ -3,18 +3,10 @@ package runtime
 
 // TODO: use the time package for this.
 
-// #include <unistd.h>
-import "C"
-
 type Duration uint64
 
 // Use microseconds as the smallest time unit
 const (
-	Microsecond = 1
 	Millisecond = Microsecond * 1000
 	Second      = Millisecond * 1000
 )
-
-func Sleep(d Duration) {
-	C.usleep(C.useconds_t(d))
-}