printf with UART - blocking way?

RE: printf with UART - blocking way?

ovrebekk — Tue, 08 Jan 2019 12:45:10 GMT

Happy to help Mathias, best of luck with your project 🙂

RE: printf with UART - blocking way?

Mathias — Mon, 07 Jan 2019 10:29:33 GMT

Ok, got it! Thanks so much for replying Torbjørn!

RE: printf with UART - blocking way?

ovrebekk — Mon, 17 Dec 2018 11:55:51 GMT

Hi Mathias

When you run the code from interrupt context you will block the UART interrupts, which prevents the UART driver from working properly to empty the UART buffers.

An alternative workaround to this is to make sure the UART interrupts run at a higher interrupt priority (lower pri number) than the interrupt context you are currently in.

Best regards
Torbjørn

RE: printf with UART - blocking way?

Mathias — Mon, 10 Dec 2018 17:25:51 GMT

Hi Torbjørn,

I'm wondering why the code gets stuck when used in the interrupt context? Why does this code only work in the main context and not in interrupt context?

Thanks.

Kind regards,

Mathias

RE: printf with UART - blocking way?

ovrebekk — Wed, 05 Sep 2018 09:13:40 GMT

Hi Andre

I just tested this myself, and as long as I make sure to run the while loop in the main (thread) context it works fine.

If I run the while loop in an interrupt context it will not work, and the code will get stuck in the while loop as described by Globuloz.

Can you confirm whether or not the code runs in main context?

Best regards
Torbjørn

RE: printf with UART - blocking way?

studzinski — Fri, 31 Aug 2018 12:31:05 GMT

We are still waiting for a fix 🙂

RE: printf with UART - blocking way?

studzinski — Mon, 22 Jan 2018 12:34:02 GMT

nRF51, SDK11. UART fifo init. I resolved this problem with estimated delay (vs. message size&baudrate) and larger FIFO size (515 bytes). Unfortunately I have already removed this control sequence. Obviously no event has fired when FIFO was empty. The event handler was well initiated in uart_init function. I will reestablish sequences & zip the project soon...

RE: printf with UART - blocking way?

ovrebekk — Mon, 22 Jan 2018 11:34:17 GMT

Which SDK version are you using?

Could you zip your project and share it, so I can have a look at the code?

Best regards

RE: printf with UART - blocking way?

studzinski — Sun, 21 Jan 2018 14:19:27 GMT

I confirm. This loop never ends. Unfortunately, it seems that this event never files in case of UART fifo initialisation. Cannot find a workarond since months!

RE: printf with UART - blocking way?

ovrebekk — Tue, 03 May 2016 11:52:13 GMT

Can you attach the code so I can have a look at it? If yes, please just zip your project and attach it to the case.

RE: printf with UART - blocking way?

Globuloz — Mon, 02 May 2016 16:06:00 GMT

Thank you for reply! I've tested the code and it seems that it is an infinite loop.

RE: printf with UART - blocking way?

ovrebekk — Mon, 02 May 2016 11:48:39 GMT

The app_uart library returns an event when the TX buffer is empty, and you can wait for this event to make the library appear blocking:

Pseudo code:

// Declare variable
static volatile bool uart_tx_in_progress = false;

// Write to the uart
uart_tx_in_progress = true;
app_uart_put(...);
while(uart_tx_in_progress);

// Excerpt from UART event handler
if(p_event->evt_type == APP_UART_TX_EMPTY)
{
uart_tx_in_progress = false;
}

Regards Torbjørn