osmo-trx with USRP1 - libusrp vs. UHD

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Alexander Huemer alexander.huemer at xx.vu
Thu Jan 18 00:12:32 UTC 2018


Hi!

On Thu, Dec 21, 2017 at 09:55:12PM +0100, Harald Welte wrote:
> On Thu, Dec 21, 2017 at 07:57:24PM +0100, Alexander Huemer wrote:
> > I played with osmo-trx today and tried to run it with a USRP1 that I 
> > have laying around, though to no avail.
> 
> I also still have two USRP1 here that don't have a purpose anymore.
> 
> My offer is: If you (or the community in general) works out how to make
> USRP1 work with current-day osmo-trx (either via UHD or via a ported
> libusrp) on a system like Debian9, I will make sure that a USRP1
> becomes part of the osmo-gsm-tester setup[1] to ensure support for this
> board will not bit-rot again.

Fair enough.

What I did so far is:
* Extract libusrp from gnuradio 3.4.2, using git filter-branch to 
  preserve history
* Craft custom configure.ac
* Update m4 macros
* Small fixes here and there

libusrp builds without warnings now and can be installed with `make 
install` as expected.

After a trivial fix of osmo-trx with `configure --with-usrp1` it starts 
without complaining.

-- Transceiver active with 1 channel(s)

Still, when I try to run a full network with 
osmo-{stp,hlr,msc,bsc,bts-trx}, osmo-bts-trx aborts with:

<000b> trx_if.c:413 transceiver (phy0.0) rejected TRX command with response: 'RSP RXTUNE 1 1763200'
<0001> bts.c:210 Shutting down BTS 0, Reason TRX-CTRL-MSG: CRITICAL
Shutdown timer expired

osmo-trx emits:

ALERT 140296268797696 00:38:04.3 USRPDevice.cpp:590:setRxFreq: set RX: 1.7632e+09failed
    baseband freq: 1.75825e+09
    DDC freq:      -4.95e+06
    residual freq: -0.00447035
ALERT 140296268797696 00:38:04.3 USRPDevice.cpp:590:setRxFreq: set RX: 1.7632e+09failed
    baseband freq: 1.75825e+09
    DDC freq:      -4.95e+06
    residual freq: -0.00447035
ALERT 140296268797696 00:38:04.3 Transceiver.cpp:766:driveControl: RX failed to tune
ALERT 140296268797696 00:38:04.3 Transceiver.cpp:766:driveControl: RX failed to tune

I don't think that my clock is too far off, I am using a freshly 
calibrated clocktamer to feed 52MHz into the USRP.

Why the USRP would not be able to tune to ARFCN 777 is not clear to me.
E.g. kalibreate has no problem with receiving all ARFCNs in DCS.

Should anybody have an idea what to look into, suggestions would be 
appreciated.

Kind regards,
-Alex
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