Hi Matt I will try this, though given P = 2, I was under the impression the resulting VCO frequency should have been 1 MHz * P * B = 100 MHz when I have B = 50. At least, that is what the equation in the datasheet suggests.
Regards Ian. -----Original Message----- From: Matt Ettus [mailto:m...@ettus.com] Sent: Tuesday, 17 August 2010 2:15 AM To: Ian Holland Cc: discuss-gnuradio@gnu.org Subject: Re: [Discuss-gnuradio] Changing external reference frequency with USRP2... On 08/16/2010 12:21 AM, Ian Holland wrote: > Thanks Matt > > I tried to change to get the external reference frequency to be 36 > MHz, by setting B to 50 (i.e. 0x32) and R to 36 (i.e. 0x24). To do > this, I modified lines 43 and 85 respectively to the following: > > ad9510_write_reg(0x06, 0x32); ad9510_write_reg(0x0C, 0x24); If you set R to 36 then your compare frequency is 1 MHz. A setting of B = 50 means you are trying to lock at 50 MHz, which won't work. The crystal is at 100 MHz, so you need to use B=100. This will cause you to be way off in frequency (maybe 100 to 150 ppm). It should still function, however. > However, when I rebuilt the firmware (txrx.bin) and wrote it to the > SD card, I was no longer able to see an OFDM signal I had been > transmitting from another SDR at 2.4 GHz. This occurred both when I > had configured the receiving SDR to lock onto the 36 MHz reference > (device->config_mimo(usrp2::MC_WE_LOCK_TO_SMA)) And when I configured > the receiving SDR to use its internal reference > (device->config_mimo(usrp2::MC_WE_DONT_LOCK)) > > Have I done something wrong in my modifications? If so, can you > please suggest what I am doing wrong? According to the AD9510 > datasheet I believe my changes should have been correct. If it doesn't work with either setting then it is likely your firmware is bad. Check to make sure you are using a good Microblaze compiler. Matt This message is intended only for the use of the intended recipient(s) If you are not an intended recipient, you are hereby notified that any use, dissemination, disclosure or copying of this communication is strictly prohibited. If you have received this communication in error please destroy all copies of this message and its attachments and notify the sender immediately _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio