diff --git a/src/machine/board_microbit.go b/src/machine/board_microbit.go
new file mode 100644
index 00000000..9a23718b
--- /dev/null
+++ b/src/machine/board_microbit.go
@@ -0,0 +1,32 @@
+// +build nrf,microbit
+
+package machine
+
+// The micro:bit does not have a 32kHz crystal on board.
+const HasLowFrequencyCrystal = false
+
+// Buttons on the micro:bit (A and B)
+const (
+	BUTTON  = BUTTON1
+	BUTTON1 = 5
+	BUTTON2 = 11
+)
+
+// UART pins
+const (
+	UART_TX_PIN = 24
+	UART_RX_PIN = 25
+)
+
+// ADC pins
+const (
+	ADC0 = 0
+	ADC1 = 1
+	ADC2 = 2
+)
+
+// I2C pins
+const (
+	SDA_PIN = 20
+	SCL_PIN = 19
+)
diff --git a/src/machine/board_pca10040.go b/src/machine/board_pca10040.go
index 3ba0c5f7..065fda19 100644
--- a/src/machine/board_pca10040.go
+++ b/src/machine/board_pca10040.go
@@ -2,6 +2,9 @@
 
 package machine
 
+// The PCA10040 has a low-frequency (32kHz) crystal oscillator on board.
+const HasLowFrequencyCrystal = true
+
 // LEDs on the PCA10040 (nRF52832 dev board)
 const (
 	LED  = LED1
diff --git a/src/machine/machine_nrf.go b/src/machine/machine_nrf.go
index 9308b9e7..f155da07 100644
--- a/src/machine/machine_nrf.go
+++ b/src/machine/machine_nrf.go
@@ -19,22 +19,25 @@ 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)
+	port, pin := p.getPortPin()
+	port.PIN_CNF[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) {
+	port, pin := p.getPortPin()
 	if high {
-		nrf.P0.OUTSET = 1 << p.Pin
+		port.OUTSET = 1 << pin
 	} else {
-		nrf.P0.OUTCLR = 1 << p.Pin
+		port.OUTCLR = 1 << pin
 	}
 }
 
 // Get returns the current value of a GPIO pin.
 func (p GPIO) Get() bool {
-	return (nrf.P0.IN>>p.Pin)&1 != 0
+	port, pin := p.getPortPin()
+	return (port.IN>>pin)&1 != 0
 }
 
 // UART
@@ -62,7 +65,7 @@ func (uart UART) Configure(config UARTConfig) {
 	nrf.UART0.INTENSET = nrf.UART_INTENSET_RXDRDY_Msk
 
 	// Enable RX IRQ.
-	arm.EnableIRQ(nrf.IRQ_UARTE0_UART0)
+	arm.EnableIRQ(nrf.IRQ_UART0)
 }
 
 // SetBaudRate sets the communication speed for the UART.
@@ -89,8 +92,7 @@ func (uart UART) WriteByte(c byte) error {
 	return nil
 }
 
-//go:export UARTE0_UART0_IRQHandler
-func handleUART0() {
+func (uart UART) handleInterrupt() {
 	if nrf.UART0.EVENTS_RXDRDY != 0 {
 		bufferPut(byte(nrf.UART0.RXD))
 		nrf.UART0.EVENTS_RXDRDY = 0x0
@@ -128,13 +130,15 @@ func (i2c I2C) Configure(config I2CConfig) {
 	}
 
 	// do config
-	nrf.P0.PIN_CNF[config.SCL] = (nrf.GPIO_PIN_CNF_DIR_Input << nrf.GPIO_PIN_CNF_DIR_Pos) |
+	sclPort, sclPin := GPIO{config.SCL}.getPortPin()
+	sclPort.PIN_CNF[sclPin] = (nrf.GPIO_PIN_CNF_DIR_Input << nrf.GPIO_PIN_CNF_DIR_Pos) |
 		(nrf.GPIO_PIN_CNF_INPUT_Connect << nrf.GPIO_PIN_CNF_INPUT_Pos) |
 		(nrf.GPIO_PIN_CNF_PULL_Pullup << nrf.GPIO_PIN_CNF_PULL_Pos) |
 		(nrf.GPIO_PIN_CNF_DRIVE_S0D1 << nrf.GPIO_PIN_CNF_DRIVE_Pos) |
 		(nrf.GPIO_PIN_CNF_SENSE_Disabled << nrf.GPIO_PIN_CNF_SENSE_Pos)
 
-	nrf.P0.PIN_CNF[config.SDA] = (nrf.GPIO_PIN_CNF_DIR_Input << nrf.GPIO_PIN_CNF_DIR_Pos) |
+	sdaPort, sdaPin := GPIO{config.SDA}.getPortPin()
+	sdaPort.PIN_CNF[sdaPin] = (nrf.GPIO_PIN_CNF_DIR_Input << nrf.GPIO_PIN_CNF_DIR_Pos) |
 		(nrf.GPIO_PIN_CNF_INPUT_Connect << nrf.GPIO_PIN_CNF_INPUT_Pos) |
 		(nrf.GPIO_PIN_CNF_PULL_Pullup << nrf.GPIO_PIN_CNF_PULL_Pos) |
 		(nrf.GPIO_PIN_CNF_DRIVE_S0D1 << nrf.GPIO_PIN_CNF_DRIVE_Pos) |
diff --git a/src/machine/machine_nrf51.go b/src/machine/machine_nrf51.go
new file mode 100644
index 00000000..29abf989
--- /dev/null
+++ b/src/machine/machine_nrf51.go
@@ -0,0 +1,17 @@
+// +build nrf51
+
+package machine
+
+import (
+	"device/nrf"
+)
+
+// Get peripheral and pin number for this GPIO pin.
+func (p GPIO) getPortPin() (*nrf.GPIO_Type, uint8) {
+	return nrf.GPIO, p.Pin
+}
+
+//go:export UART0_IRQHandler
+func handleUART0() {
+	UART0.handleInterrupt()
+}
diff --git a/src/machine/machine_nrf52.go b/src/machine/machine_nrf52.go
index f62c10f1..1022df58 100644
--- a/src/machine/machine_nrf52.go
+++ b/src/machine/machine_nrf52.go
@@ -7,6 +7,16 @@ import (
 	"unsafe"
 )
 
+// Get peripheral and pin number for this GPIO pin.
+func (p GPIO) getPortPin() (*nrf.GPIO_Type, uint8) {
+	return nrf.P0, p.Pin
+}
+
+//go:export UARTE0_UART0_IRQHandler
+func handleUART0() {
+	UART0.handleInterrupt()
+}
+
 // InitADC initializes the registers needed for ADC.
 func InitADC() {
 	return // no specific setup on nrf52 machine.
diff --git a/src/runtime/runtime_nrf.go b/src/runtime/runtime_nrf.go
index 06754950..893a48a0 100644
--- a/src/runtime/runtime_nrf.go
+++ b/src/runtime/runtime_nrf.go
@@ -28,7 +28,9 @@ func init() {
 }
 
 func initLFCLK() {
-	nrf.CLOCK.LFCLKSRC = nrf.CLOCK_LFCLKSTAT_SRC_Xtal
+	if machine.HasLowFrequencyCrystal {
+		nrf.CLOCK.LFCLKSRC = nrf.CLOCK_LFCLKSTAT_SRC_Xtal
+	}
 	nrf.CLOCK.TASKS_LFCLKSTART = 1
 	for nrf.CLOCK.EVENTS_LFCLKSTARTED == 0 {
 	}
diff --git a/targets/arm.ld b/targets/arm.ld
index 1cf41783..59bbf34b 100644
--- a/targets/arm.ld
+++ b/targets/arm.ld
@@ -10,6 +10,7 @@ SECTIONS
         *(.text*)
         *(.rodata)
         *(.rodata*)
+        . = ALIGN(4);
     } >FLASH_TEXT
 
     /* Put the stack at the bottom of RAM, so that the application will
diff --git a/targets/microbit.json b/targets/microbit.json
new file mode 100644
index 00000000..02f4fc26
--- /dev/null
+++ b/targets/microbit.json
@@ -0,0 +1,25 @@
+{
+	"llvm-target": "armv6m-none-eabi",
+	"build-tags": ["microbit", "nrf51822", "nrf51", "nrf", "arm", "js", "wasm"],
+	"linker": "arm-none-eabi-gcc",
+	"pre-link-args": [
+		"-nostdlib",
+		"-nostartfiles",
+		"-mcpu=cortex-m0",
+		"-mthumb",
+		"-T", "targets/nrf51.ld",
+		"-Wl,--gc-sections",
+		"-fno-exceptions", "-fno-unwind-tables",
+		"-ffunction-sections", "-fdata-sections",
+		"-Os",
+		"-DNRF51",
+		"-Ilib/CMSIS/CMSIS/Include",
+		"lib/nrfx/mdk/system_nrf51.c",
+		"src/device/nrf/nrf51.s"
+	],
+	"objcopy": "arm-none-eabi-objcopy",
+	"flash": "openocd -f interface/cmsis-dap.cfg -f target/nrf51.cfg -c 'program {hex} reset exit'",
+	"ocd-daemon": ["openocd", "-f", "interface/cmsis-dap.cfg", "-f", "target/nrf51.cfg"],
+	"gdb": "arm-none-eabi-gdb",
+	"gdb-initial-cmds": ["target remote :3333", "monitor halt", "load", "monitor reset", "c"]
+}
diff --git a/targets/nrf51.ld b/targets/nrf51.ld
new file mode 100644
index 00000000..442ae1b0
--- /dev/null
+++ b/targets/nrf51.ld
@@ -0,0 +1,10 @@
+
+MEMORY
+{
+    FLASH_TEXT (rw) : ORIGIN = 0x00000000, LENGTH = 256K /* .text */
+    RAM (xrw)       : ORIGIN = 0x20000000, LENGTH = 16K
+}
+
+_stack_size = 2K;
+
+INCLUDE "targets/arm.ld"
diff --git a/tools/gen-device-svd.py b/tools/gen-device-svd.py
index ab361d13..0fd1ecf4 100755
--- a/tools/gen-device-svd.py
+++ b/tools/gen-device-svd.py
@@ -54,19 +54,16 @@ def readSVD(path, sourceURL):
         if groupNameTags:
             groupName = getText(groupNameTags[0])
 
-        for interrupt in periphEl.findall('interrupt'):
+        interruptEls = periphEl.findall('interrupt')
+        for interrupt in interruptEls:
             intrName = getText(interrupt.find('name'))
             intrIndex = int(getText(interrupt.find('value')))
-            if intrName in interrupts:
-                if interrupts[intrName]['index'] != intrIndex:
-                    raise ValueError('interrupt with the same name has different indexes: ' + intrName)
-                interrupts[intrName]['description'] += ' // ' + description
-            else:
-                interrupts[intrName] = {
-                    'name':        intrName,
-                    'index':       intrIndex,
-                    'description': description,
-                }
+            addInterrupt(interrupts, intrName, intrIndex, description)
+            # As a convenience, also use the peripheral name as the interrupt
+            # name. Only do that for the nrf for now, as the stm32 .svd files
+            # don't always put interrupts in the correct peripheral...
+            if len(interruptEls) == 1 and deviceName.startswith('nrf'):
+                addInterrupt(interrupts, name, intrIndex, description)
 
         if periphEl.get('derivedFrom') or groupName in groups:
             if periphEl.get('derivedFrom'):
@@ -150,6 +147,20 @@ def readSVD(path, sourceURL):
 
     return device
 
+def addInterrupt(interrupts, intrName, intrIndex, description):
+    if intrName in interrupts:
+        if interrupts[intrName]['index'] != intrIndex:
+            raise ValueError('interrupt with the same name has different indexes: %s (%d vs %d)'
+                % (intrName, interrupts[intrName]['index'], intrIndex))
+        if description not in interrupts[intrName]['description'].split(' // '):
+            interrupts[intrName]['description'] += ' // ' + description
+    else:
+        interrupts[intrName] = {
+            'name':        intrName,
+            'index':       intrIndex,
+            'description': description,
+        }
+
 def parseRegister(groupName, regEl, baseAddress, bitfieldPrefix=''):
     regName = getText(regEl.find('name'))
     regDescription = getText(regEl.find('description'))
@@ -400,8 +411,10 @@ Default_Handler:
 '''.format(**device.metadata))
     num = 0
     for intr in device.interrupts:
+        if intr['index'] == num - 1:
+            continue
         if intr['index'] < num:
-            raise ValueError('interrupt numbers are not sorted or contain a duplicate')
+            raise ValueError('interrupt numbers are not sorted')
         while intr['index'] > num:
             out.write('    .long 0\n')
             num += 1