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Re: [Discuss-gnuradio] Reading registers on the USRP


From: Eric Blossom
Subject: Re: [Discuss-gnuradio] Reading registers on the USRP
Date: Thu, 14 Feb 2008 09:33:26 -0800
User-agent: Mutt/1.5.17 (2007-11-01)

On Thu, Feb 14, 2008 at 12:06:34PM -0500, address@hidden wrote:
> I've read that post before.  It more or less gave me reassurances on what
> I had gathered that had to be done to implement a simple in-line
> multiplier in the TX chain.  The post tells me what registers are
> readback, but not how to read them back.  When I came across the post
> originally, it pointed me in the right direction to where I should connect
> the output of my new module.
> 
> -Kevin

First off please note that readable registers and writable registers
are in two different, non-overlapping address spaces.

If you create a readable register, you can read it's value using

  v = u._read_fpga_reg (int regno)


Eric

> > address@hidden wrote:
> >> Hi,
> >>
> >> I'm having a little trouble reading the readback registers that are on
> >> the
> >> USRP.  I know that most registers are write only with their contents
> >> mirrored on the computer.  The reason I want read those registers back
> >> is
> >> because of a custom unit I am testing.  I currently load a custom
> >> implementation on the USRP that consists of 1 TX chain and 2 custom
> >> units,
> >> one of which feeds back information into the unused readback ports
> >> (rssi0
> >> to rssi3). I'm able to read from the capabilities register using
> >> '_read_fpga_register(FR_RB_CAPS)' and it returns a value that makes
> >> sense.
> >>  When I try reading from any other register, the value returned is
> >> consistently '0'.  I'm reading the registers in a loop in case the value
> >> changes after a given amount of time.  I'm not sure what to try next,
> >> can
> >> someone give me a new direction?
> >>
> >> -Kevin
> >
> > This post might help:
> >
> > http://lists.gnu.org/archive/html/discuss-gnuradio/2007-05/msg00356.html
> >
> > -Roshan




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