esp32-uart-echo

esp32-uart-echo

This example demonstrates how to use the ESP-IDF UART driver from Swift to create a simple echo application. It wraps the ESP-IDF UART APIs in a Swift-friendly Uart struct and redirects Swift's standard I/O (print() and readLine()) to a custom UART port. This example is specifically made for the RISC-V MCUs from Espressif (the Xtensa MCUs are not currently supported by Swift).

Features

• Swift wrapper around ESP-IDF UART driver APIs
• Redirect stdin/stdout/stderr to a custom UART port
• Use Swift's native readLine() and print() for UART communication
• Simple echo functionality: receives data and sends it back

Requirements

• Set up the ESP-IDF development environment. Follow the steps in the ESP32-C6 "Get Started" guide.

  • Make sure you specifically set up development for RISC-V based Espressif chips, and not the Xtensa based products.

• Before trying to use Swift with the ESP-IDF SDK, make sure your environment works and can build the provided C/C++ sample projects, in particular:

  • Try building and running the "get-started/hello_world" example from ESP-IDF written in C.

Building

• Make sure you have a recent nightly Swift toolchain that has Embedded Swift support.
• If needed, run export.sh to get access to the idf.py script from ESP-IDF.
• Specify the target board type by using idf.py set-target. Any RISC-V based Espressif chip is supported.

$ cd esp32-uart-echo
$ . <path-to-esp-idf>/export.sh
$ idf.py set-target esp32c6 # or esp32c3, esp32p4, etc.
$ idf.py build

Running

This example uses ESP32-C6 as a reference, but any RISC-V based Espressif chip can be used. Adjust the GPIO pins according to your development kit.

• Connect your board over a USB cable to your computer.
• Connect a USB-UART converter to the configured UART pins (example for ESP32-C6):
  • TX (GPIO20) -> RX on USB-UART converter
  • RX (GPIO19) -> TX on USB-UART converter
  • GND -> GND on USB-UART converter
• Use idf.py to upload the firmware:

$ idf.py flash

• Open a serial terminal (e.g., picocom, minicom, or screen) connected to the USB-UART converter at 115200 baud:

$ picocom -b 115200 /dev/ttyUSB0

• Type text and press Enter. The text will be echoed back to you.

Configuration

The default UART configuration in Main.swift:

• Port: UART1
• TX Pin: GPIO20
• RX Pin: GPIO19
• Baud Rate: 115200

To change these settings, modify the Uart initialization in Main.swift:

let uart = Uart(portNum: 1, txPin: 20, rxPin: 19, baudRate: 115200)