UART FIFO Flush: How to determine that UART TX is completed

[Comodo]

Hi everyone,

in our project we transmit from an android app to Nordic BLE big amount of data (up to 180.000 bytes). I do it by using hvx notifications (MTU 247) and each time I get the notification I try to transmit the data over UART. But we have realized that the uart TX takes too much time and causes packet loss. So I have decieded to store the BLE data and send it after the BLE notifications are completed. Now I face the problem that the UART FIFO (2048) will be full and causes system fault. I need to find out a way where I can determine when the TX transmition is completed and I can flush the TX buffer. I ve searched the uart driver but could find the right function for that. Can anyone help me regarding that?

Thx and Regards

[Andy]

You should get NRFX_UART_EVT_TX_DONE on the event handler.

[Comodo]

You mean "APP_UART_TX_EMPTY" ?

[Andy]

Ah, if you're using the app_uart library then yes. But then I don't understand your problem with flushing the FIFO. I've never used that library, but I assume it flushes the buffers by itself.

[Andy]

Nevermind, just saw the API.

[Comodo]

Hi still got this problem

I fill the Tx buffer and wait until it has been sent but that doesnt happen it stacks there. 

[ovrebekk]

Hi 

Are you able to disable notifications on the characteristic temporarily to avoid the client on the Android side sending more data until the UART has had time to flush the buffers?

Then you could disable the notifications once you have received a certain amount of data, wait for the APP_UART_TX_EMPTY event to occur, and enable notifications again. 

This probably requires the addition of some code in the app to verify if notifications are enabled before uploading data to the Bluetooth stack. 

Best regards
Torbjørn