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
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