Align UART transmission/reception with GPIO pin signaling low/high

[bscdb]

How do I align UART transmission/reception with GPIO pin signaling low/high? I wanted to do this because BLE chip is receiving the Product ID & device name from microcontroller over uart & it is also sending the HID output reports over uart. The steps/logic I would like to implement -

(A) After receiving the Product ID & device name, pull GPIO pin low. (There is more logic included)

I tried this but the pin goes low, before all data is read. I was tracking the error code to return NRF_SUCCESS but that does not help. I was trying to do something like this for app_uart_put() & app_uart_get()

for(ind = 0; ind < BLE_INFO_FRAME_LEN; ind++)
	{
		//NRF_LOG_RAW_INFO("Byte: %d\n", ble_info_frame[ind]);
		while (app_uart_put(ble_info_frame[ind]) != NRF_SUCCESS);
	}
	if(ind == BLE_INFO_FRAME_LEN)
	{
		nrf_gpio_pin_clear(0);
	}

(B) After transmitting HID output report, pull GPIO pin high

Is there a flag or interrupt which tracks this?

[Håkon Alseth]

Hi,

 

I tried this but the pin goes low, before all data is read. I was tracking the error code to return NRF_SUCCESS but that does not help. I was trying to do something like this for app_uart_put() & app_uart_get()

Try setting the signal inactive in the uart event handler, upon event "APP_UART_TX_EMPTY". This should align the pin with the UART transmission.

(B) After transmitting HID output report, pull GPIO pin high

If I understand your scenarios correctly (and please; correct me if I am mistaken), you want to set the pin again after transmitting a given data stream. This would then be equal to your first scenario.

 

Kind regards,

Håkon

[bscdb]

Hey Hakon, I have already tried using APP_UART_TX_EMPTY. I'm using SDK 15.2 & a combination of HID keyboard & Peripheral UART example. When I use APP_UART_TX_EMPTY in uart error handler, the bluetooth connection gets affected so that's why I removed it. Do you know why this happens?

[Håkon Alseth]

What was the code that you added to the event handler?

[bscdb]

My error handler 

void uart_error_handle(app_uart_evt_t * p_event)
{
	uint32_t err_code;	
	switch(p_event->evt_type)
	{			
	    case APP_UART_TX_EMPTY:
	        nrf_gpio_pin_clear(0);
	    break;
		case APP_UART_COMMUNICATION_ERROR:
			break;
		case APP_UART_FIFO_ERROR:
			break;
		default:
			break;
	}
}

[bscdb]

Please reply..

[Håkon Alseth]

Hi,

 

I am very sorry for the late reply. The app_uart library sends byte-for-byte, so you're right: this will not work properly.

You could do something like this:

for(ind = 0; ind < BLE_INFO_FRAME_LEN; ind++)
	{
		//NRF_LOG_RAW_INFO("Byte: %d\n", ble_info_frame[ind]);
		while (app_uart_put(ble_info_frame[ind]) != NRF_SUCCESS);
	}
	// If last byte, set flag to clear pin in uart_handler()
	if(ind == BLE_INFO_FRAME_LEN)
	{
		clear_pin = true;
	}

 And in the uart handler:

void uart_error_handle(app_uart_evt_t * p_event)
{
	uint32_t err_code;	
	switch(p_event->evt_type)
	{			
	    case APP_UART_TX_EMPTY:
	        if (clear_pin == true)
	        {
	            clear_pin = false;
	            nrf_gpio_pin_clear(0);
	        }
	    break;
		case APP_UART_COMMUNICATION_ERROR:
			break;
		case APP_UART_FIFO_ERROR:
			break;
		default:
			break;
	}
}

Could you try this and see if it works better?

 

Another alternative can be to call nrf_drv_uart_tx() directly, as you can then set the length of the overall transmission in one transaction.

 

Kind regards,

Håkon