Re: [Discuss-gnuradio] found problem with std_4rx_0tx.rbf and unrelated bugs in rx_chain.v

[Martin Dvh]

Hans Glitsch wrote:
> Ok,  I found that the bug was introduced into std_4rx_0tx.rbf at version
> 4848.  Version 4287 does not have the problem.

The changes in changeset 4713 looked suspicious.
"Refactored FPGA *.vh files. Moved common pieces to toplevel/include. "
But I couldn't find any obvisous mistakes there.

Then I generated a complete diff between r 4287 and 4848 the following way:
$ cd usrp
$ svn diff -r 4287:4848

But I didn't find any mistakes there even.
It is also possible that something went wrong when generating std_4rx_0tx.rbf.
Has anybody tried rebuilding it (with Quartus II) with the current trunk code 
(r 4848 or later)

When looking further into the code for the RX_chain I did find a few 
(unrelated) bugs in
usrp/fpga/sdr_lib/rx_chain.v
When the NCO is turned off (RX_NCO_ON is not defined)
then sample_strobe is assigned to 1
However sample_strobe is an input, so this will fail.

The same mistake is made for decimator_strobe when the CIC is turned off.

It can be solved by adding wires for sample_strobe_internal and 
decimator_strobe_internal and assigning to that in stead.

This probably hasn't surfaced because at the moment NCO and CIC are always 
enabled.
see lines 31,32, 64 and 74 below.

usrp/fpga/sdr_lib/rx_chain.v
31         input sample_strobe,
32         input decimator_strobe,
...

51      `ifdef RX_NCO_ON
52          phase_acc #(FREQADDR,PHASEADDR,32) rx_phase_acc
53           (.clk(clock),.reset(reset),.enable(enable),
54            
.serial_addr(serial_addr),.serial_data(serial_data),.serial_strobe(serial_strobe),
55            .strobe(sample_strobe),.phase(phase) );
56      
57         cordic rx_cordic
58           ( .clock(clock),.reset(reset),.enable(enable),
59             .xi(i_in),.yi(q_in),.zi(phase[31:16]),
60             .xo(bb_i),.yo(bb_q),.zo() );
61      `else
62         assign bb_i = i_in;
63         assign bb_q = q_in;
64         assign sample_strobe = 1;
65      `endif // !`ifdef RX_NCO_ON
66      
67      `ifdef RX_CIC_ON
68         cic_decim cic_decim_i_0
69           ( .clock(clock),.reset(reset),.enable(enable),
70             
.rate(decim_rate),.strobe_in(sample_strobe),.strobe_out(decimator_strobe),
71             .signal_in(bb_i),.signal_out(hb_in_i) );
72      `else
73         assign hb_in_i = bb_i;
74         assign decimator_strobe = sample_strobe;
75      `endif


Greetings,
Martin
> 
> Hans
> 
> 
> ----- Original Message ----- From: "Johnathan Corgan"
> <address@hidden>
> To: "Eric Blossom" <address@hidden>
> Cc: "Hans Glitsch" <address@hidden>; <address@hidden>
> Sent: Wednesday, October 24, 2007 10:57 AM
> Subject: Re: [Discuss-gnuradio] found problem with std_4rx_0tx.rbf
> 
> 
>> Eric Blossom wrote:
>>
>>> I can reproduce it.  There's definitely something off with
>>> std_4rx_0tx.rbf.
>>> I've opened ticket:195  http://gnuradio.org/trac/ticket/195
>>>
>>> [This is all I'm going to do about this right now.]
>>
>> Since that RBF has only been re-synthesized a couple of times in the
>> last year or so, it would be straightforward to manually replace the
>> file with the versions from 3.0 series, and see where the problem
>> started.  I think there will be at most 4 versions to test.  You
>> wouldn't need to change the host code any, just get the proper RBF from
>> the repository and manually install into $prefix/share/usrp/rev2 and 4.
>>
>> -- 
>> Johnathan Corgan
>> Corgan Enterprises LLC
>> http://corganenterprises.com
>>
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> 
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