Example app - UART bridge

Message format

Simulated device will use third register ([><][mac]/[serial]/3) as pipe channel, so any publishing into this register will lead transmitting this data into TTY, and vice-versa.
Any data received in TTY will be forwarded to this register. Internally TTY have 10ms as maximum interval between symbols, on timeout - message will be transmitted into mqtt.

Linux

Under linux os, application will try to create a PTY pipe (/tmp/uart) . That pipe could be opened with any terminal, for example tio or miniterm on any available speed

Example:

$ python3 -m serial.tools.miniterm /tmp/uart  
--- Miniterm on /tmp/uart  9600,8,N,1 ---  
--- Quit: Ctrl+] | Menu: Ctrl+T | Help: Ctrl+T followed by Ctrl+H ---  
"hello mqtt"

Micropython (ESP32-C3)

Device based on ESP32 will use UART0 as default uart device, RX and TX pins will be mapped to 20 and 21 pin respectively. This configuration could be changed in esp32.json board definition file. UART is using 115200 8N1 configuration.

REPL, in the same time, will be available at internal USB Serial port (details: https://docs.espressif.com/projects/esp-idf/en/latest/esp32c3/api-guides/usb-serial-jtag-console.html)

Also, to use such configuration, Micropython build set MICROPY_HW_ENABLE_UART_REPL to zero. Check ports/esp32/boards/ESP32_GENERIC_C3/mpconfigboard.h

Already built Micropython release with these changes could be found in other/esp32-c3_wo_repl folder, and could be 'burned' by deploy.sh script (needed esptool.py)

Device related registers

On real device, except 3-rd register also available, registers 3,4,5,6. Where:

• Register 3 - UART Pipe, which silently transfers data from MQTT to BLE and to UART, and vice-versa
• Register 4 - Color of internal LED on ESP32-C3-DevKitM-1
  • Used RGB integer format, ie to set red diode color - need to write 16711680 value (converted from hex - 0xff0000)
• Register 5 - Used to send SMS, and due to current limitation will work only via wifi connection, but with presence SIM-card. To force connection to wifi option use register 6
  • Used JSON format: {"to":"+3812345678", "msg": "Message which should be sent"}
• Register 6 - Used to force WIFI connection, if set this register to 1, device will reboot and try to establish a connection via WIFI instead of GSM/LTE. To set default value, write into it - 0

Windows