diff --git a/ports/stm32/mboot/fwupdate.py b/ports/stm32/mboot/fwupdate.py
new file mode 100644
index 0000000000..b2690e8cda
--- /dev/null
+++ b/ports/stm32/mboot/fwupdate.py
@@ -0,0 +1,172 @@
+# Update Mboot or MicroPython from a .dfu.gz file on the board's filesystem
+# MIT license; Copyright (c) 2019 Damien P. George
+
+import struct, time
+import uzlib, machine, stm
+
+
+FLASH_KEY1 = 0x45670123
+FLASH_KEY2 = 0xcdef89ab
+
+
+def check_mem_contains(addr, buf):
+    mem8 = stm.mem8
+    r = range(len(buf))
+    for off in r:
+        if mem8[addr + off] != buf[off]:
+            return False
+    return True
+
+def check_mem_erased(addr, size):
+    mem16 = stm.mem16
+    r = range(0, size, 2)
+    for off in r:
+        if mem16[addr + off] != 0xffff:
+            return False
+    return True
+
+def dfu_read(filename):
+    f = open(filename, 'rb')
+
+    hdr = f.read(3)
+    f.seek(0)
+    if hdr == b'Dfu':
+        pass
+    elif hdr == b'\x1f\x8b\x08':
+        f = uzlib.DecompIO(f, 16 + 15)
+    else:
+        print('Invalid firmware', filename)
+        return None
+
+    elems = []
+
+    hdr = f.read(11)
+    sig, ver, size, num_targ = struct.unpack('<5sBIB', hdr)
+
+    file_offset = 11
+
+    for i in range(num_targ):
+        hdr = f.read(274)
+        sig, alt, has_name, name, t_size, num_elem = struct.unpack('<6sBi255sII', hdr)
+
+        file_offset += 274
+        file_offset_t = file_offset
+        for j in range(num_elem):
+            hdr = f.read(8)
+            addr, e_size = struct.unpack('<II', hdr)
+            data = f.read(e_size)
+            elems.append((addr, data))
+            file_offset += 8 + e_size
+
+        if t_size != file_offset - file_offset_t:
+            print('corrupt DFU', t_size, file_offset - file_offset_t)
+            return None
+
+    if size != file_offset:
+        print('corrupt DFU', size, file_offset)
+        return None
+
+    hdr = f.read(16)
+    hdr = struct.unpack('<HHHH3sBI', hdr)
+
+    return elems
+
+def flash_wait_not_busy():
+    while stm.mem32[stm.FLASH + stm.FLASH_SR] & 1 << 16:
+        machine.idle()
+
+def flash_unlock():
+    stm.mem32[stm.FLASH + stm.FLASH_KEYR] = FLASH_KEY1
+    stm.mem32[stm.FLASH + stm.FLASH_KEYR] = FLASH_KEY2
+
+def flash_lock():
+    stm.mem32[stm.FLASH + stm.FLASH_CR] = 1 << 31 # LOCK
+
+def flash_erase_sector(sector):
+    assert 0 <= sector <= 7 # for F722
+    flash_wait_not_busy()
+    cr = (
+        2 << 8 # PSIZE = 32 bits
+        | sector << 3 # SNB
+        | 1 << 1 # SER
+    )
+    stm.mem32[stm.FLASH + stm.FLASH_CR] = cr
+    stm.mem32[stm.FLASH + stm.FLASH_CR] = cr | 1 << 16 # STRT
+    flash_wait_not_busy()
+    stm.mem32[stm.FLASH + stm.FLASH_CR] = 0
+
+def flash_write(addr, buf):
+    assert len(buf) % 4 == 0
+    flash_wait_not_busy()
+    cr = (
+        2 << 8 # PSIZE = 32 bits
+        | 1 << 0 # PG
+    )
+    stm.mem32[stm.FLASH + stm.FLASH_CR] = cr
+    for off in range(0, len(buf), 4):
+        stm.mem32[addr + off] = struct.unpack_from('I', buf, off)[0]
+        flash_wait_not_busy()
+    stm.mem32[stm.FLASH + stm.FLASH_CR] = 0
+
+def update_mboot(filename):
+    print('Loading file', filename)
+
+    mboot_fw = dfu_read(filename)
+    if mboot_fw is None:
+        return
+    if len(mboot_fw) != 1:
+        assert 0
+    mboot_addr, mboot_fw = mboot_fw[0]
+    if mboot_addr != 0x08000000:
+        assert 0
+
+    # TODO: Validate firmware in a simple way
+
+    print('Found Mboot data with size %u.' % len(mboot_fw))
+
+    chk = check_mem_contains(mboot_addr, mboot_fw)
+    if chk:
+        print('Supplied version of Mboot is already on device.')
+        return
+
+    print('Programming Mboot, do not turn off!')
+    time.sleep_ms(50)
+
+    irq = machine.disable_irq()
+    flash_unlock()
+    flash_erase_sector(0)
+    if len(mboot_fw) > 16 * 1024 and not check_mem_erased(mboot_addr + 16 * 1024, 16 * 1024):
+        flash_erase_sector(1)
+    flash_write(mboot_addr, mboot_fw)
+    flash_lock()
+    machine.enable_irq(irq)
+
+    print('New Mboot programmed.')
+
+    if check_mem_contains(mboot_addr, mboot_fw):
+        print('Verification of new Mboot succeeded.')
+    else:
+        print('Verification of new Mboot FAILED!  Try rerunning.')
+
+    print('Programming finished, can now reset or turn off.')
+
+def update_mpy(filename, fs_base, fs_len):
+    # Check firmware is of .dfu.gz type
+    try:
+        with open(filename, 'rb') as f:
+            hdr = uzlib.DecompIO(f, 16 + 15).read(6)
+    except Exception:
+        hdr = None
+    if hdr != b'DfuSe\x01':
+        print('Firmware must be a .dfu.gz file.')
+        return
+
+    ELEM_TYPE_END = 1
+    ELEM_TYPE_MOUNT = 2
+    ELEM_TYPE_FSLOAD = 3
+    ELEM_MOUNT_FAT = 1
+    mount_point = 1
+    mount = struct.pack('<BBBBLL', ELEM_TYPE_MOUNT, 10, mount_point, ELEM_MOUNT_FAT, fs_base, fs_len)
+    fsup = struct.pack('<BBB', ELEM_TYPE_FSLOAD, 1 + len(filename), mount_point) + bytes(filename, 'ascii')
+    end = struct.pack('<BB', ELEM_TYPE_END, 0)
+    machine.bootloader(mount + fsup + end)