----- Original Message ----- From: Eric Blossom <address@hidden> Date: Monday, January 18, 2010 9:09 pm Subject: Re: [Discuss-gnuradio] default DAC setting To: Yan Nie <address@hidden> Cc: address@hidden
> On Tue, Jan 19, 2010 at 07:03:37AM +0800, Yan Nie wrote: > > Dear all, > > > > What's the default setting, if python doesn't write any > register in > > AD9862. For example, in gr-sounder project there isn't any > > configuration for AD9862 chip. > > > > Thanks in advance > > > > Regards, > > Yan > > gr-sounder (sounder.py) uses usrp.sink_s to talk to the USRP, > thus it > uses the default values that are written by usrp_basic* and > usrp_standard* > Look in usrp/host/lib/usrp_{basic,standard}.cc for the details. > > Eric
Hi,
Thank you Eric. I looked at the usrp_basic.cc file, and have several questions on it.
1. the default AD9862 reg setting is in the following, is it correct? master clock for FPGA: 64MHz; sample_rate going to D/A: 128MHz / 4 ; Tx out puts will be static and Tx analog power down; DAC A Offset is 0; the output current is not scales ; No gain adjustment for the DAC output curve; TxPGA gain is maximum gain: 0 dB; DAC input rate 64MHz; NCO disabled; coarse modulator disabled ' interpolate 4x; zero Tx Auto Tansmit/Receive reg;
2. Why the DAC input rate is 64MHz but the sample_rate is 32MHz. If the sample_rate is the Nyquist frequency, the tx data rate should be lower than 16MHz, but here the DAC input rate is 64MHz, why?
3. What's the difference among functions tx_tune(target_freq), set_tx_freq(target_freq), and using fine modulation in DAC? What's the difference among these three approach for shifting the data in baseband to RF in pass band?