Re: [Discuss-gnuradio] USRP2 dropping data

[David Evans]

After much ado...

The VRT branch I have always returns zero for rx_missing() and rx_overruns(), 
with a FIXME comment. I notice this is now fixed in the latest git.

I also found no problems of lost data using Ubuntu 9.10 on an older Zotac 
motherboard, it wasn't until I moved to the H55-itx, and had to get the latest 
e1000 ethernet driver, that the missing data issue appeared. I then had the 
problem using the later driver on the older motherboard, which confused me. I 
wil try the later git code... 

Checking the fractional timestamps of the received packets I found that the 
receive samples handler always reports the same nitems (365 in my case with a 
10MHz sample rate = 3650), but the fractional count itself sometimes updates 
(with the new intel ethernet driver) by a multiple of this value (eg 3x), but 
because I'm using nitems to fwrite the data to disk, data was being skipped. 
I've not had a chance to check the latest git, but hopefully this is fixed.

Yes, config_mimo isn't there, I was trying to go by memory, which isn't what it 
used to be, or ever was...:-o


Yes UHD looks the way to go, but loks to be another learning curve and rewrite 
of code I've done already.

Cheers


----- Original Message ----
From: Per Zetterberg <address@hidden>
To: David Evans <address@hidden>
Sent: Mon, 17 May, 2010 20:30:12
Subject: Re: [Discuss-gnuradio] USRP2 dropping data

David Evans wrote:
> Hi,
> 
> setup...
> -2x USRP2s + GPS 10MHz reference + 1PPS
> -Single GigE port, with USRPs on GigE switch
> -Zotac H55-itx MB + i3 processor, so quite high end.
> -VRT branch code. I also use PPS via DCD line to trigger when to load time on 
> next PPS, enable real time scheduling, ref to SMA, pps to SMA, 
> config_mimo(MC_WE_LOCK_TO_SMA) and use similar code to rx_streaming_samples 
> (but 2x USRPs).
> -decimation set to 10
> -feeding in same off tune carrier into RFX400s to get a sine wave, just to 
> observe sync.
> And yet, after sampling 30 seconds of data to file from both USRPs and the 
> code reports 0 underruns, 0 lost packets, no S's,  I often get 
> dropouts/missed packets.
> As I am receiving only, I gather from various posts that a single eth port + 
> switch should be Ok. The data captured always starts off in sync, it just 
> goes wrong sometime during the capture. The number of bytes captured is 
> normally the same for both channels too.
> 
> Hope you can help please,
> 
> 
>      
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>  

I have used VRT and everything has worked so far.  However, I didn't do 
"config_mimo(MC_WE_LOCK_TO_SMA)" I did 
"c.ref_source=usrp2::clock_config_t::REF_SMA;" and "u2->config_clock(c);". Is 
"config_mimo" really part of the host VRT code ?

In any case, you and me should start to use UHD instead .....