Re: [Discuss-gnuradio] CORDIC in USRP TX path

[Christian Meier]

Matt Ettus wrote:
> Christian Meier wrote:
> > Hi,
> > I noticed that there is a hardcoded "`define NOCORDIC_TX" inside 
> > tx_chain.v
> >
> > Does anyone know why this is disabled?
> > Is it a problem of FPGA size or are there any bugs inside tx_chain 
> > with NOCORDIC_TX not defined?
>
>
> Ignore my last answer.  We use the RX cordic.  The TX cordic is not 
> used because there is the equivalent functionality in the AD9862 DAC, 
> so we don't need to include it in the FPGA, and thus can save space.
>
> Matt
Hi once more,
I am currently writing a patch that reactivates the disabled and out of 
date integration of the tx cordic inside FPGA.
If this works and fits into the FPGA, I plan to use it for getting more 
tx and rx channels over the same daugtherboard with different baseband 
offsets.
For this to work the tx and rx pipelines of a 2rx + 2tx configuration 
have to be combined after tx_chain / before rx_chain.
This is done in a tx_combiner module.

Find attached the current progress as a patch. [Update: posting did not 
work with attached file ;(]
I haven't neither tested nor synthesized it yet at all. I just wanted to 
give a base for discussion.
If someone has any comments or further ideas on that, please let me know.

By the way, what is the firmware/fpga_regs0.h file good for? I didn't 
find any file that uses these defines, or any .v file that includes 
fpga_regs0.v.
For the patch to compile we also need some new register definitions of 
FR_TX_(FREQ|PHASE)_[01] and FR_TX_COMBINER.

What do you think of this idea?
Thanks

Christian