NUS example UART RX can't receive all data

[Felix Shih]

NCS v2.7.0

peripheral_uart (nRF52832-DK)

central_uart (nRF52840-DK)

PC console -> JLink VCOM -> BLE peripheral(nRF52832-DK) -> BLE central (nRF52840-DK) -> JLink VCOM -> PC console 

1) send 240 bytes (repeat "0123456789" to form one 240 bytes packet) from PC UART in 100ms interval to peripheral_uart side, UART RX central_uart side sometimes can't receive all data in PC UART, like 

...01234567890127890123456789...

lost 4 bytes.

2) modify peripheral_uart and central_uart according to thread 

 nRF Connect SDK NUS throughput modifications and issues for peripheral_uart/central_uart example applications 

3) add 

CONFIG_UART_0_NRF_HW_ASYNC=y

CONFIG_UART_0_NRF_HW_ASYNC_TIMER=1

according to thread

 Data Loss With Nordic Uart Service 

4) attached my projects for reference.

central_uart_v270_test_241008.7z

peripheral_uart_v270_test_241008.7z

[Susheel Nuguru]

Tested peripheral on nrf52832 and central on nrf52840 dk. Not sure how you are sending the bytes from central to peripheral but I tried to do it manually from terminal and the reception looked ok

Did not see any missing bytes

I did not use adruino in the overlap file but instead had this in app.overlay

&uart0 {
	status = "okay";
	current-speed = <1000000>;
	hw-flow-control;
};

[Felix Shih]

Hi, thanks for your test.

1) To send just once mostly ok, but I need to send the bitmap file from peripheral to central about 2MB, so the usage is like the stress test.
To send the 2MB from BLE peripheral to central in the maximum throughput, I use 100ms interval for test, although it is still too slow to transfer the 2MB bitmap file. I also use wireshark to sniffer the BLE packets and they are send without loss, the loss is in UART RX.

2) For example, I send 21600 bytes, but RX receive 21580 bytes only from UART terminal.

3) I attached uart assist tool, if you want to use it for test.

uartassist5.0.3.7z

[Susheel Nuguru]

Can you lower the baudrate to 115200 and see if that works, to test if this is caused by some bottlenecks at those high speed. I think there are some bottlenecks either in the application of the in uart library or driver that show up at those high speeds you are using. At those high speeds, there is a need to consider the pre and post processing latencies per serial transactions. 

[Felix Shih]

Using baudrate with 115200bps, Rx still lost data. I think the original UART flow can't handle the stress test like this.

[Susheel Nuguru]

we use 115200bps all the time with larger data chunks and it works fine and the URAT on 52840 is very mature peripheral.

I do not think this is an issue with the hardware. I tried to send chunk data in loop of 100 and it is working fine at my end, no garbled or missing data at my end.

[Felix Shih]

Hi Susheel Nuguru ,

It seems our 115200 bps tests are different.

Can you attach your two 115200 bps projects including BLE peripheral and central for me to test on my own environment? I will try your projects on my own and close this ticket.

Thanks for your help.