Changing UART1 baud rate on runtime for ESP32C3 doesn't seem to work

[abdulhayub]

Hi everyone,

I'm working on changing UART1 baud rate on runtime, on ESP32C3. I have tried using uart_configure and uart_line_ctrl_set but both of them don't seem to work i.e. they execute without actually changing the baud rate and don't return a negative error code. The communication simply stops. Moreover, the uart_config_get reports the same baud rate before and after changing it.

Here's the relevant prj.conf:

# UART
CONFIG_SERIAL=y
CONFIG_UART_INTERRUPT_DRIVEN=y
CONFIG_UART_USE_RUNTIME_CONFIGURE=y
CONFIG_UART_LINE_CTRL=y
CONFIG_UART_DRV_CMD=y

And the relevant .dts section:

&uart1 {
	status = "okay";
	current-speed = <115200>;
	pinctrl-0 = <&uart1_tx_gpio19 &uart1_rx_gpio18 &uart1_cts_gpio2 &uart1_rts_gpio3>;
	pinctrl-names = "default";
};

And here's the relevant code:

int configure_device_uart_baud_rate(uint32_t device_uart_baud_rate)
{
	int error = 0;

	const struct device *uart_device = DEVICE_DT_GET(DT_ALIAS(uart1));
	if (uart_device == NULL) {
		LOG_ERR("UART Device not found");
		return -ENODEV;
	}

	error = device_is_ready(uart_device);
	if (error != 1) {
		LOG_ERR("UART Device not ready (error %d)", error);
		return error;
	}

	struct uart_config uart_config;
	error = uart_config_get(uart_device, &uart_config);
	if (error) {
		LOG_ERR("uart_config_get failed (error %d)", error);
		return error;
	}
	LOG_DBG("UART current baud rate = %lu", (unsigned long)uart_config.baudrate);

	/* This doesn't work either */
	// error = uart_line_ctrl_set(uart_device, UART_LINE_CTRL_BAUD_RATE, device_uart_baud_rate);
	// if (error) {
	// 	LOG_ERR("uart_line_ctrl_set failed (error %d)", error);
	// 	return error;
	// }

	uart_config.baudrate = device_uart_baud_rate;
	LOG_DBG("UART setting baud rate = %lu", (unsigned long)uart_config.baudrate);

	error = uart_configure(uart_device, &uart_config);
	if (error) {
		LOG_ERR("uart_line_ctrl_set failed (error %d)", error);
		return error;
	}

	error = uart_config_get(uart_device, &uart_config);
	if (error) {
		LOG_ERR("uart_config_get failed (error %d)", error);
		return error;
	}
	LOG_DBG("UART updated baud rate = %lu", (unsigned long)uart_config.baudrate);

	return error;
}

Environment:

• Devcontainer based on image: zephyrprojectrtos/zephyr-build:v0.25.0
• Toolchain Zephyr SDK 0.16.0
• Zephyr branch: v3.3.0
• Target: esp32c3 (DevkitM-1)

Are there any insights to what may be the problem here?