UART API

Implement UART serial communication in custom chips

To create an UART device, first call uart_init, passing in an uart_config_t struct. This struct defines the RX/TX pins, the baud rate, and the rx/write_done callbacks.

uart_init

uart_dev_t uart_init (const uart_config_t *config)

Initializes UART device. The config argument defines the pins, configuration, and callbacks for the UART device. It contains the following fields:

rx · pin_t

The RX pin (or NO_PIN to disable RX)

tx · pin_t

The TX pin (or NO_PIN to disable TX)

baud_rate · uint32_t

The baud rate (e.g. 115200)

rx_data · callback

Called for each byte received on the RX pin

write_done · callback

Called when data transmission on the TX pin has finished

user_data · void *

Data that will be passed in the first argument of the callbacks

Both of the callbacks (rx_data, write_done) are optional. They all use the user_data pointer as their first argument.

Example

static void on_uart_rx_data(void *user_data, uint8_t byte) {
  // `byte` is the byte received on the "RX" pin
}

static uint8_t on_uart_write_done(void *user_data) {
  // You can write the chunk of data to transmit here (by calling uart_write).
}

// ...

const uart_config_t uart1 = {
  .tx = pin_init("TX", INPUT_PULLUP),
  .rx = pin_init("RX", INPUT),
  .baud_rate = 115200,
  .rx_data = on_uart_rx_data,
  .write_done = on_uart_write_done,
  .user_data = chip,
};

uart_write

bool uart_write (uart_dev_t uart, uint8_t *buffer, uint32_t count)

Write count bytes from the memory pointed to by buffer to the given uart device.
Returns true on success, or false if the UART device is already busy transmitting data from a previous uart_write call (and the new data won’t be transmitted).

The data starts transmitting after uart_write returns. Once Wokwi finishes transmitting the data, the write_done callback is called (from the uart_config_t structure that you passed to uart_init).

Simulator examples

• UART ROT13 Chip Example