The muwerk serial protocol uses the munet muserial.h module to make MQTT available to devices that are
not networked using a serial bridge.
Hardware: Adafruit Feather32 ESP32, 5V <-> 3.3V logic level shifter, Arduino Mega 2560, led + 330 Ohm resistor, button.
The MCUs used are just examples, you can of course use different modules. Just adapt platform.ini and the
platform defines in src/bridge.cpp accordingly.
The ESP32 MCU is connected to the network and an extern MQTT server (as configured in data/net.json and
data/mqtt.json). Via Serial1, the ESP32 is connected to the Arduino Mega 2560's Serial2 (via a logic level
shifter to convert 3.3V levels to 5V). The Arduino is connected to a led and a switch (via Led and Switch muwerk
mupplets from mupplets-core).
To the outside world, the system of ESP32 and Arduino Mega 2560 appears as a single system. Both sub-systems can publish and subscribe to MQTT, all message synchronisation is handled automatically via the serial link.
Let's assume the ESP has hostname bridge-test and the name of the serial link given to the Arduino is arduino.
The led is named l1 and the switch is named s1 during mupplet instantiation (see code).
Let's switch on the Arduino's Led using MQTT:
mosquitto_pub -h <mqtt-server-hostname> -t bridge-test/l1/light/set -m on
The led on the Arduino goes on!
Let's listen to messages from ESP32:
mosquitto_sub -h <mqtt-server-hostname> -v -t omu/bridge-test/#
Sending a led command again (from a second terminal) shows:
omu/bridge-test/l1/light/set on
omu/bridge-test/l1/light/unitbrightness 1.0
omu/bridge-test/l1/light/state on
Let's press the button that is connected to the Arduino:
omu/bridge-test/s1/switch/state on
omu/bridge-test/s1/switch/state off
From a second terminal, we can reconfigure both button and led:
mosquitto_pub -h <mqtt-server-host> -t bridge-test/l1/light/mode/set -m "wave 2000"
# The led connected to the Arduino now pulses in waves every 2000ms
mosquitto_pub -h <mqtt-server-host> -t bridge-test/s1/switch/mode/set -m flipflop
# Now the button acts as flipflop: every press/release, the state is changed only once.
We can use muwerk's mutop.py tool,
to watch the processes both on the ESP32 and on the Arduino using an MQTT connection:
$ python mutop.py <insert-mqtt-server-host> bridge-test
Connected to MQTT server <mqtt-server-host>.
Subscribing to omu/bridge-test/$SYS/stat
-------------------------------------------------------------------------
ID Task name Schedule Cnt task rel time cputime/call late/call
-------------------------------------------------------------------------
1 serial 60ms 33 1.830% ▏ 5.42µs 627.55µs
2 serlink 5ms 392 14.575% █▌ 3.64µs 103.06µs
3 net 100ms 20 37.388% ███▊ 182.90µs 7.60µs
4 mqtt 100ms 20 10.272% █ 50.25µs 7.35µs
5 ota 25ms 79 35.875% ███▋ 44.43µs 325.10µs
6 main 1 s 2 0.061% 3.00µs 8.50µs
-------------------------------------------------------------------------
Free memory 237132 bytes, uptime: 00000000:46:47
CPU: 0.546% | Δ: 2000013µs, OS: 118103µs, App: 1790303µs
-------------------------------------------------------------------------
Note: serial is the serial console of muwerk (see below), and serlink is
the connection to the Arduino.
Note: we append /arduino (the name of the MuSerial link of the Arduino)
to the hostname of the ESP32:
$ python mutop.py <mqtt-server-host> bridge-test/arduino
Connected to MQTT server <mqtt-server-host>.
Subscribing to omu/bridge-test/$SYS/stat
-------------------------------------------------------------------------
ID Task name Schedule Cnt task rel time cputime/call late/call
-------------------------------------------------------------------------
1 serial 60ms 33 2.622% ▎ 17.09µs 729.33µs
2 serlink 5ms 388 53.459% █████▍ 29.64µs 165.49µs
3 l1 50ms 40 38.062% ███▉ 204.70µs 112.70µs
4 s1 50ms 40 5.764% ▋ 31.00µs 112.50µs
5 main 1 s 2 0.093% 10.00µs 60.00µs
-------------------------------------------------------------------------
Free memory 3748 bytes, uptime: 00000000:13:09
CPU: 1.157% | Δ: 2000004µs, OS: 75088µs, App: 1859068µs
-------------------------------------------------------------------------
The Arduino has the additional processes l1 (for the led) and s1 (for the switch). Communication from and to those via mqtt is handled transparently by MuSerial.
The example code instantiated a muwerk Console on the default Serial connection
of both ESP32 and Arduino Mega. That serial connection is available via the USB
connection to the computer used for programming.
After editing the correct port names in platform.ini, the console can be accessed
using platformio's pio tool via pio device monitor -e feather32 for the ESP32
and pio device monitor -e mega for the Arduino (feather32 and mega are the environment
names given in platform.ini.
We get a prompt:
pio device monitor -e mega
--- Available filters and text transformations: colorize, debug, default, direct, hexlify, log2file, nocontrol, printable, send_on_enter, time
--- More details at http://bit.ly/pio-monitor-filters
--- Miniterm on /dev/tty.usbserial-2220 115200,8,N,1 ---
--- Quit: Ctrl+C | Menu: Ctrl+T | Help: Ctrl+T followed by Ctrl+H ---
muwerk> help
commands: help, pub, sub, uname, uptime, ps, info, mem
muwerk> sub #
All topics subscribed
>> s1/switch/state on
>> s1/switch/state off
muwerk>
The example show monitoring the messages on the Arduino mega using the serial console, the button was pressed,
and the messages s1/switch/state on/off are visible in the console.
- In data directory, copy
net-default.jsontonet.jsonandmqtt-default.jsontomqtt.json - Customize
net.jsonandmqtt.json, used by ESP32 to connect to the network and MQTT. - Customoze
platform.iniand adaptupload_portandmonitor_portfor both build targets. - Build filesystem:
pio run -t buildfs -e feather32for ESP32 - Upload filesystem:
pio run -t uploadfs -e feather32for ESP32 - Upload program code:
pio run -t upload, this uploads to both Arduino and ESP32.