Re: [Discuss-gnuradio] putchar function

[Christoph Thein]

> On Mon, Feb 01, 2010 at 05:57:04PM +0100, Christoph Thein wrote:
> > Hi,
> >
> > I am trying to figure out how it is possible to get more than the "U"
> > message from the USRP2 to the host via the UART port but I am stucked at
> > some point. When I try to transmit other characters than "U" I am
> > receiving something completely unpredictable (at least it looks like that
> > to me at the moment). I am using the putchar-function in the txrx.c file
> > in the firmware/apps directory with the gnuradio version
> > 3.3git-601-g18578e23 .
> >
> > I dug deeper into the code and tried the hal_uart_putc function also but
> > with no results.
> >
> > Does anyone have an idea how to achieve a working signaling throught the
> > UART port?
> >
> > Thanks a lot,
> > Cheers,
> > Christoph
> 
> Christoph,
> 
> It's just about impossible to get anything more than a few characters
> out in the hard real-time part of the code (pretty much everything
> after start-up), without causing a problem.  This is because we don't
> have "infinite buffering", and eventually the code calling the uart
> output primitive blocks, causing all kinds of bad things to happen.
> You could make the uart output code interrupt driven, but in general,
> that will only buy you another 128 bytes or so (whatever memory you're
> willing to dedicate to the buffer) before the problem occurs.
> 
> If you've got a logic analyzer to grab the data, and the ISE tools,
> it's not too hard to add an additional "setting register" that when
> written to, will end up on the mictor debug connector on the
> motherboard, or on the GPIO pins of a Tx or Rx Basic/LF daughterboard.
> (In lib/memory_map.h add an entry to output_regs_t, and add the
> setting register itself in fpga/top/u2_core/u2_core.v).
> 
> Eric
> 


Hi Eric,

thanks! 
I just want to get a 16 bit value to the host, so basically only a few 
characters. 

BR
Christoph