On Sun, Jun 17, 2012 at 4:21 AM, Alexander Chemeris alexander.chemeris@gmail.com wrote:
Alternatively I recommend you to use this image which is tested and known to work fine (either bin for usrp_n2xx_net_burner.py or bit for JTAG): http://code.google.com/p/umtrx/downloads/detail?name=u2plus_umtrx-20120424.b... http://code.google.com/p/umtrx/downloads/detail?name=u2plus_umtrx-20120424.b...
Ok. With this FPGA image and the following initialization sequence, I get signal. OpenBTS output is pretty clean as shown in the attachment. Note that I halved the GSM symbol rate because for some strange reason, I was not able to run OpenBTS with two samples-per-symbol, though I was able to send a tone with tx_waveforms at the same sample rate.
So this is 'slow' GSM at 135 kHz, but the point was to get sampling above Nyquist to capture any distortion from the device and not OpenBTS itself. There is noticeable IQ imbalance, but I guess that is just uncorrected. Also, please ignore the failure messages on our test equipment (we have a converter spec issue).
Is there a similar sequence to enable Rx?
Thomas
Looks like it is not correctly initialized. Try using the same initialization sequence as I do:
./umtrx_lms.py --lms 1 --lms-init ./umtrx_lms.py --lms 1 --lms-tx-enable 1 #./umtrx_lms.py --lms 1 --lms-rx-enable 1 # Select 0.75MHz LPF ./umtrx_lms.py --lms 1 --reg 0x34 --data 0x3e ./umtrx_lms.py --lms 1 --pll-ref-clock 26e6 --lpf-bandwidth-code 0x0f --lms-auto-calibration # Manual DC calibration ./umtrx_lms.py --lms 1 --reg 0x42 --data 0x71 ./umtrx_lms.py --lms 1 --reg 0x43 --data 0x89 ../build/utils/uhd_cal_tx_dc_offset --compl_i 0.001 --compl_q 0 # Tuning ./umtrx_lms.py --lms 1 --lms-tx-pll-tune 925e6 ./umtrx_lms.py --lms 1 --lms-pa-on 2
