ESP32 OTA firmware update simple example

[chaseadam]

Here is a basic example of an OTA Partitions update for Micropython firmware on the ESP32. There are several solutions for updating the code running on the device, but I didn't find an end to end example using the OTA functions to update the firmware. Hope this is useful to others.

This was the most basic end to end example I could build. There are likely many layers (i.e. verification, etc.) and likely improvements (python structure) to be made.

Uses socket esp32.Partition

The following will take whatever is streamed over the socket and write it to the "next" partition. I created a socket server with the following:

nc -vkl 8889 < micropython.bin

I found the micropython.bin in ./build-GENERIC_OTA/ after building micropython with BOARD=GENERIC_OTA make. This represents the Partition contents whereas the firmware.bin includes all the partitions and bootloader.

I have hard coded port 8889.

The default partition table allows for 384 sectors per partition. Sectors are 4096 bytes, so this should work for any micropython.bin file which is less than 1572864 bytes (latest upstream build used 368 sectors).

My replconf.py file contains:

ssid="<SSID>"
password="<WPA2 PSK>"
# if you need to connect to specific access point (due to connecting to bad/far access point)
#bssid=b"\xaa\xbb\xcc\xdd\xee\xff"
bssid=None

otaplay.py

# this will write the contents returned by socket connection to the "next" partition
from esp32 import Partition
import socket
from time import sleep
from machine import reset
import replconf as rc

def do_connect(hostname = False):
    import network
    sta_if = network.WLAN(network.STA_IF)
    if not sta_if.isconnected():
        sta_if.active(True)
        print('connecting to network...')
        # TODO remove hard coded BSSID and figure out how to connect to the "strongest" signal
        sta_if.connect(rc.ssid,rc.password, bssid=rc.bssid)
        while not sta_if.isconnected():
            print('.', end = '')
            sleep(0.25)
    try:
        host = sta_if.config('hostname')
    except ValueError:
        # "hostname" is available in master, but not yet in June 2022 1.19.1 release
        host = sta_if.config('dhcp_hostname')
    print('Wifi connected as {}/{}, net={}, gw={}, dns={}'.format(
        host, *sta_if.ifconfig()))

# TODO: test connection stablility before updating
def update():
    host = 'example.com'
    SEC_SIZE = 4096
    buf = bytearray(SEC_SIZE)
    i = 0
    currentPartition = Partition(Partition.RUNNING)
    nextPartition = currentPartition.get_next_update()
    assert nextPartition.ioctl(5,0) == SEC_SIZE
    SEC_COUNT = nextPartition.ioctl(4,0)
    addr = socket.getaddrinfo(host, 8889)[0][-1]
    s = socket.socket()
    s.connect(addr)
    print("connected")
    while True:
        if i > SEC_COUNT:
            print("attempt to write more sectors than available")
        buf = s.read(SEC_SIZE)
        if buf:
            print(i)
            print(len(buf))
            if len(buf) < SEC_SIZE:
                print('adding padding to sector')
                buf = buf + bytes(b'\xff'*(4096 - len(buf)))
            nextPartition.writeblocks(i, buf)
            i += 1
        else:
            break
    s.close()

do_connect()

Run with:

import otaplay
otaplay.update()

If you want to boot to the other partition:

from esp32 import Partition
currentPartition = Partition(Partition.RUNNING)
nextPartition = currentPartition.get_next_update()
nextPartition.set_boot()
import machine; machine.reset()

and if you wish to not rollback to the previous partition after boot, you must call currentPartition.mark_app_valid_cancel_rollback()