C UART API usage example

Overview

This example demonstartes how to use C UART API. For mJS API usage example see here.

By default, mOS is configured to use UART0 for system console: this is where both stdout and stderr are routed. UART1 is unused, making it available for user applications. We will assume this configuration in our example.

It will print hello message to UART1 every second and echo whatever is received on UART1 to UART0 (console).

Platform support

It should work on all supported architectures.

• On ESP8266 UART1 TX is GPIO2. UART1 RX is inaccessible, so it is not possible to send anything.
• On ESP32, by default, UART1 TX is GPIO26 and RX is 25.
• On CC3200 - 7 and 8 respectively (these are pin numbers, not GPIO).

Controlling console output

It is possible to reconfigure console output to different UART or disable console output entirely: it is controlled by the debug.stdout_uart and debug.stderr_uart configuration settings. Defaults for both are 0, setting to 1 will send output to UART1 and setting to a negative value will disable output. This is especially useful on ESP8266, where UART0 is the only bidirectional UART (there is no UART2, despite what some diagrams may suggest by showing RXD2 and TXD2 functions).

Early diagnostic output (before configuration file is read) is controlled by the MGOS_DEBUG_UART compile-time option.

Running

See quick start guide on how to build and flash the firmware. Below is an example session:

mos build        # Build the firmware
mos flash        # Flash the firmware
mos console      # Attach a serial console and see device logs