Sending data without a delimiter using the nordic uart service (NUS) sample - Dropping bytes

Question

I'm developing my application using the NRF Connect SDK in VS code. SDK Version 2.4.2. The NRF52832f we're using is integrated into a module made by fanstel and it has been assembled on our own internal ECU that interfaces with another microcontroller. We're wanting to use the nordic uart service (NUS) to transfer data from one device to another, in this case using two circuit boards but in the future one of the boards will be replaced by a smart phone. 
 In our project we're sending binary data using the nordic uart service profile with the peripheral uart service sample application connected to the central uart service sample application on a different evaluation board. I added a periodic uart flush which disables the uart (code example below) because I don't have a delimiter character to indicate data is done being sent but I think this potentially makes me drop bytes when the central may receive bytes over it's physical UART between the time I disable the UART and before it's enabled again. I see bytes drop frequently, using a BLE sniffer and also confirmed via inspection in the RTT console, which is causing serious throughput issues. 
 Does anyone have any experience with this? I'm also concerned that even if I do designate a delimiter like 
 the process of disabling/renabling the uart in the uart interrupt as is done in the sample project will still make bytes drop if more messages are sent in short succession after this. Does anyone have the UART peripheral running without enable/disable anywhere and without delimiters? Thanks in advance! 
 
 void uart_timeout_flush(void)
{
	for (;;) {
 if(uart_bytes_read > 0u)
 {
 uart_bytes_read = 0;
 LOG_INF("UART Flush: ");
 disable_req = true;
 uart_rx_disable(uart);
 }
 k_sleep(K_MSEC(50));
	}
}

K_THREAD_DEFINE(uart_timeout_flush_thread_id, UART_FLUSH_STACKSIZE, uart_timeout_flush, NULL, NULL,
 NULL, UART_FLUSH_PRIO, 0, 0);

ovrebekk · Accepted Answer

Hi Nick 
 This sounds like what the timeout parameter in the UART async driver was designed for, to forward the data in the buffers to the application if there has been no activity on the bus for a pre-determined amount of time. 
 Have you tried this? 
 You might also want to have a look at an example I made which intends to streamline the UART interface when using the ASYNC driver: https://github.com/too1/ncs-uart-handler 
 Best regards Torbjørn

ovrebekk · Answer

Hi Nick 
 This could be related to an issue in the UART async driver when using the default interrupt based byte counting method. You can optionally enable a hardware counting feature which uses more peripherals, but ensures byte counting is handled without CPU interaction required. 
 In order to enable this you can have a look at these configuration parameters . 
 Could you add these configs and see if it solves the issue? 
 Please note you need to change the name of the parameters if you want to use a different UART or TIMER module. 
 Best regards Torbjørn

Sending data without a delimiter using the nordic uart service (NUS) sample - Dropping bytes

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