I've been playing with the gr-digital OFDM benchmark, Tx -> Rx, and have an odd issue that seems to be coming from within GNU Radio itself, not UHD. My setup is: Mac OS X 10.6.8, latest UHD and GNU Radio from their respective GIT masters, XCode 3.2.3 (gcc 4.2.1). I'm using 2 USRP1's, each with an XCVR2450 (in slot A, using antenna J1), connected to my MacBook Pro (via USB 2.0). 'uhd_usrp_probe' and 'uhd_find_devices' both work correctly in finding and identifying both USRP1's. 'uhd_fft.py' seems to work
After installing GNU Radio into /usr/local, if I do in one terminal (or, the equivalent in GRC), with XXX correct: pushd /usr/local/share/gnuradio/examples/digital/ofdm ./benchmark_rx.py -a serial=XXX --spec A:0 -A J1 -f 5e+9 --snr 10 and in another (or, the equivalent in GRC), with YYY correct: pushd /usr/local/share/gnuradio/examples/digital/ofdm ./benchmark_tx.py -a serial=YYY --spec A:0 -A J1 -f 5e+9 The Rx side shows nothing at all. So, I then used 'uhd_fft.py' to view the spectrum, and it looks like the Tx (or, Rx) is off by quite a bit -- high by ~1 MHz. So, correcting via: ./benchmark_tx.py -a serial=YYY --spec A:0 -A J1 -f 4.999e+9 works quite well, with most of the packets being Rx'd correctly. I've verified that swapping XXX and YYY has the same results, so it doesn't seem to matter which is doing Rx and which Tx. I then created my own program in C/C++ to do a Tx using the UHD library, making a multi-usrp and setting its various parameters as per the above CLIs, then transmitting a real (complex part all 0) sinusoid of a known frequency, and it displays (using 'uhd_fft.py') correctly centered just off 5 GHz (like, maybe 1 kHz off, which is within device tolerance). I've looked through the benchmark's codes (mostly the Python parts, but also some of the blocks in C++), and nothing pops out as an obvious issue. I tried "rm -rf" in /usr/local and my build directories (UHD and GNU Radio), then rebuilding and reinstalling both UHD and GNU Radio, but with the same results. Can anyone tell me what I'm not doing correctly, or suggest further tests to track down the issue? I highly suspect it's user error :) but I'm truly at a loss right now as to the error. Thanks! - MLD _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
