Lecture 7 - UART: Universal Asynchronous Read and Write

UART. Lesing av og skriving til serieporten. Forklaring av baudrate.

UART

pass

Exercise: Send data from your board to PC

On the STM32CubeMX

Launch STM32CubeMX.
Start a New Project:
- Click File > New Project or click the New Project icon.
- In the Board Selector tab, search for NUCLEO-F767ZI.
- Select the board and click Start Project.
Select No when prompted for the default configuration.
Go to System Core > RCC: Set HSE to Crystal/Ceramic Resonator.
Configure UART (USART3)
- In the Pinout & Configuration tab:
- Navigate to Connectivity > USART3.
- Set Mode to Asynchronous. - In the Configuration tab for USART3, set the following Parameter Settings:
- Baud Rate: 115200
  (This must match your platformio.ini and code.)
- Word Length: 8 Bits (Including parity)
- Parity: None
- Stop Bits: 1
- Data Direction: Receive and Transmit
To be able to see the serial port output without changing any hardware, using the same USB port we use for uploading code, we must select the right pin numbers. As you activate USART3, the default Tx and Rx pins are PB10 and PB11. However, ST-Link uses PD8 and PD9 for this. Just click on the pin PB10 as you press Ctrl button, and drag this pin on top of the PD8. Afterwards, do the same for PB11->PD9.
Adjust the clock settings as needed for your board as show in figure.
Click Project > Generate Code to create your project files.
Give a good project name and generate code.

On the Platformio

Inside platformio.ini:

[env:nucleo_f767zi]
platform = ststm32
board = nucleo_f767zi
framework = stm32cube
build_flags = 
 -IInc
upload_protocol = stlink
debug_tool = stlink
monitor_speed = 115200 ; Set the baud rate for the serial monitor

The UART baud rate you set in CubeMX (e.g., 115200) must match the baud rate you use in your serial terminal (such as PuTTY, Tera Term, or PlatformIO Monitor). If they do not match, you will see garbled or no output.

Inside main.c, between /* USER CODE BEGIN Includes */
```
 #include<string.h>
```

Inside main.c, between /* USER CODE BEGIN 3 */

 uint8_t value = 5;
 HAL_UART_Transmit(&huart3, &value, 1, HAL_MAX_DELAY); 
 HAL_GPIO_TogglePin(LD1_GPIO_Port, LD1_Pin);
 HAL_Delay(500);

Also observe the Logic analyzer output on Rx pin on CN5 connector: 500ms delay

What if we want to send a string data?

    const char *message = "Hello world from HAL_UART_Transmit!\r\n";
    HAL_UART_Transmit(&huart3, (uint8_t *)message, strlen(message), HAL_MAX_DELAY);
    HAL_GPIO_TogglePin(LD1_GPIO_Port, LD1_Pin);
    HAL_Delay(500);

After the upload, you should press the socket icon, or Ctrl + Alt + S to open serial monitor and see this output: Also observe the Logic analyzer output: 500ms delay

Warning: Pay attention that the type of your data is important. String data is converted into ASCII. When we sent data:5 as integer and observed the binary value of 5. However, if we sent data:5 as string, we wouldn’t see its binary value on the logic analyzer, but it’s ASCII code. const char *message = "5\n"; HAL_UART_Transmit(&huart3, (uint8_t *)message, strlen(message), HAL_MAX_DELAY); ASCII 5

Exercise: Send data between two boards