ESP32 Forum

Hi

I'm calling uart_param_config() like this:

uart_config_t uartConfig;
uartConfig.baud_rate = baudrate;
uartConfig.data_bits = UART_DATA_8_BITS;
uartConfig.parity = UART_PARITY_DISABLE;
uartConfig.stop_bits = UART_STOP_BITS_1;
uartConfig.flow_ctrl = UART_HW_FLOWCTRL_DISABLE;
uartConfig.rx_flow_ctrl_thresh = 1000/*bufferSize*/ *9/10;
uartConfig.use_ref_tick = false;

err = uart_param_config (UART_NUM_1, &uartConfig);

and I get this error:

E (3559) uart: uart_set_hw_flow_ctrl(276): rx flow thresh error

If I use a smaller buffer size like 100 it works ok.
Any ideas about this?

thanks

First of all, I don't think this field will have any effect with uartConfig.flow_ctrl set to UART_HW_FLOWCTRL_DISABLE. Secondly, this is a hardware feature and the threshold is measured against how full the UARTs hardware FIFO is; as such it cannot be set to a larger value than the amount of bytes available in that FIFO.

Thanks and understood.
It seems that the routine checks the field rx_flow_ctrl_thresh even when flow_ctrl is set to UART_HW_FLOWCTRL_DISABLE!
And therefore generates the error.

yeah when filling out the structure like that, you need to explicitly set the thresh field to 0, otherwise it gets filled with stack garbage hence makes esp-idf throw an error.