How to know the remaining room in UART fifo?

RE: How to know the remaining room in UART fifo?

Chris Ergo — Sat, 05 Mar 2022 01:53:07 GMT

I still had to edit app_uart_fifo.c, but I wrote this function instead because I prefer it (less code, and returns 0 for no space instead of -1):

uint32_t app_uart_free(void) 
{
    uint32_t free = 0;
    app_fifo_write(&m_tx_fifo, NULL, &free);
    return (free);
}

RE: How to know the remaining room in UART fifo?

studzinski — Thu, 14 Feb 2019 16:36:16 GMT

What splendid idea 🙂

Have a good evening

Andre

RE: How to know the remaining room in UART fifo?

awneil — Thu, 14 Feb 2019 15:55:23 GMT

It's just one file!

If you really don't want to modify it, then take a copy and use that.

RE: How to know the remaining room in UART fifo?

studzinski — Thu, 14 Feb 2019 15:45:50 GMT

OK, thank you.

You are right. However, it is exactly what I would like to avoid... (to modify library files).

It is pity that there is no another, more elegant, way without modifying library.
BTW, it would be very logical to add such function to UART fifo management library...

Cordially

Andre

RE: How to know the remaining room in UART fifo?

awneil — Thu, 14 Feb 2019 15:09:50 GMT

Yes - as I said earlier:

Either you need to put that code into the app_uart_fifo.c file - because that's the only place where m_tx_fifo is in scope
Or you make m_tx_fifo global

RE: How to know the remaining room in UART fifo?

studzinski — Thu, 14 Feb 2019 15:01:15 GMT

The function app_fifo _write() is just what I used.
This is a generic function and can be (I suppose) applied to all fifi using the same structure.
UART fifo has the same data structure...

I know to write a function using this library. I think the only problem is the UART fifo variable scope...

I asked you for help, just to not write my own redundant code, because such fifo is already initialized by APP_UART_FIFO_INIT macro...

Cordially

Andre

RE: How to know the remaining room in UART fifo?

awneil — Thu, 14 Feb 2019 14:12:32 GMT

Ah - you're looking at app_uart_fifo, which uses the app_fifo library.

app_uart_fifo doesn't expose an app_uart_fifo _write() - so you will have to write your own.

eg, using the code from https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.sdk5.v14.2.0/lib_fifo.html?cp=4_0_2_3_14_7#lib_app_fifo_size :

int32_t app_uart_fifo_free( void )
{
   uint32_t err_code;
   uint32_t data_len;

   // Request number of elements that can be written to the FIFO
   err_code = app_fifo_write(&m_tx_fifo, NULL, &data_len);
   
   // Check if request was successful
   if (err_code == NRF_SUCCESS)
   {
       // data_len contains the number of bytes that can be written
       return data_len;
   }
   else if (err_code == NRF_ERROR_NO_MEM)
   {
       // FIFO is full
       return -1;
   }
   else
   {
      // API parameters incorrect, should not happen
      retrun -2;
   }
}

(just typed into the forum - untested)

RE: How to know the remaining room in UART fifo?

awneil — Thu, 14 Feb 2019 13:35:00 GMT

[quote userid="16701" url="~/f/nordic-q-a/43716/how-to-know-the-remaining-room-in-uart-fifo/171134"]Is there any direct way in 14.2 SDK library without writing a custom fifo??[/quote]

Surely, you've already answered that - use the app_fifo_write() function ?

You just need to use a buffer that is in-scope at the point of the call

infocenter.nordicsemi.com/.../lib_fifo.html

RE: How to know the remaining room in UART fifo?

studzinski — Thu, 14 Feb 2019 12:46:32 GMT

Of course, I said ARM, because I use it...

But my question was simple:

How to know the UART fifo remaining room (initialized by UART_FIFO_INIT macro)?

Is there any direct way in 14.2 SDK library without writing a custom fifo??

Cordially

Andre

RE: How to know the remaining room in UART fifo?

awneil — Thu, 14 Feb 2019 12:35:32 GMT

[quote userid="16701" url="~/f/nordic-q-a/43716/how-to-know-the-remaining-room-in-uart-fifo/171128"]as static, so the ARM compiler limits the scope to the file[/quote]

That's what the 'C' standard defines - nothing specifically to do with ARM!

If you want the symbol to be accessible from outside that file, you will either have to make it global, or provide an "accessor" function.

Or you could use a buffer of your own?

RE: How to know the remaining room in UART fifo?

studzinski — Thu, 14 Feb 2019 12:31:20 GMT

The m_tx_fifo variable is well declared in app_uart_fifo.c. However as static, so the ARM compiler limits the scope to the file. And I do not want to write anything in library file...

The app_fifo_write(&m_tx_fifo, NULL, &data_len); is used to get the room, as specified in the library documentation...

My question is: do you know an another way to get the remaining room in fifo, or the way to know a pointer to actual (assigned) UART fifo in order to use this function?

Cordially

Andre

RE: How to know the remaining room in UART fifo?

awneil — Thu, 14 Feb 2019 12:08:57 GMT

[quote userid="16701" url="~/f/nordic-q-a/43716/how-to-know-the-remaining-room-in-uart-fifo"] I do not know how to get a pointer to the tx fifo buffer[/quote]

That doesn't seem to have anything to do with the question of finding the remaining space in the buffer?

Surely, if you have the buffer, then getting a pointer to it is just basic 'C' ? Please clarfiy what you've tried, and where you're stuck.

[quote userid="16701" url="~/f/nordic-q-a/43716/how-to-know-the-remaining-room-in-uart-fifo"]..\..\..\main.c(1041): error: #20: identifier "m_tx_fifo" is undefined[/quote]

It's telling you that you have not defined 'm_tx_fifo' - so you need to define it!

The 'C' programming language requires that you declare things before you use them ...