How to achieve serial communication between STM32 and ESP8266?

To achieve serial communication between an STM32 and an ESP8266, you typically use UART (Universal Asynchronous Receiver-Transmitter), which both devices support. Here's a step-by-step guide:

 1. Physical Connection

• STM32 UART Pins (e.g., USART1 TX/RX) → Connect to → ESP8266 RX/TX

• Be careful: STM32 TX → ESP8266 RX, and STM32 RX ← ESP8266 TX

 Voltage Compatibility

• ESP8266 uses 3.3V logic — DO NOT use 5V on its RX pin!

• Make sure your STM32 is also running at 3.3V.

• If STM32 is 5V, use a level shifter or resistor divider for STM32 TX → ESP8266 RX.

 2. STM32 Code (HAL-based example)

Initialize UART in STM32CubeMX or STM32CubeIDE:

 3. ESP8266 Setup

The ESP8266 typically runs AT firmware (default), allowing you to send AT commands via serial to control it.

Example AT commands:

 4. UART Parameters (Must Match)

 5. Testing

• You can first test with a USB-to-Serial converter connected to ESP8266 and a terminal (e.g., PuTTY) to see if AT commands are working.

• Then move to STM32 controlling the ESP.

 6. Troubleshooting Tips

• Use an oscilloscope or logic analyzer to verify UART signals.

• Check HAL_StatusTypeDef return values for errors.

• Ensure AT firmware is installed. If using custom firmware (like NodeMCU), the command set will differ.

• Make sure the ESP8266 isn’t resetting from insufficient power — it can draw 300mA+ during Wi-Fi activity. Use a solid 3.3V regulator like AMS1117-3.3.

 Alternatives

You can also flash the ESP8266 with custom firmware (e.g., using Arduino or ESP-IDF) and define your own serial protocol for communication with the STM32.