Hi, all,
I am having a USRP E312 and is working on implementing a stepped frequency
radar application. The bandwidth of the radar is 1 GHz and the frequency step
size is 10 MHz. My current implementation is similar to the example code
“txrx_loopback_to_file.cpp” : a transmit thread sending a same baseband signal
at the background; a loop handling the tuning center frequency and receiving
data to a buffer.
The following shows the code snippets.
1. the transmit thread: just sending a same baseband signal continuously
void transmit_worker (std::vector<std::complex<float>> buff, \
uhd::tx_streamer::sptr tx_streamer, \
uhd::tx_metadata_t metadata, \
int num_channels) \
{
std::vector<std::complex<float>\*> buffs(num_channels, &buff.front());
```
// send data until the signal handler gets called
while (not stop_signal_called) {
// send the entire contents of the buffer
tx_streamer->send(buffs, buff.size(), metadata);
metadata.start_of_burst = false;
metadata.has_time_spec = false;
}
// send a mini EOB packet
metadata.end_of_burst = true;
tx_streamer->send("", 0, metadata);
```
}
2. the loop handling the tuning and receiving:
I use the usrp.get_time_now() function to timing the loop. Here is what I’ve
found: The uhd ad9361 seems to run a calibration procedure when there is a
frequency jump over 100 MHz. And each calibration takes about 2 seconds for my
measurements. With my current setup (100 steps and 10 MHz frequency step size),
the total time of the loop is 25.6 seconds. There are 9 calibrations in the
loop which takes 18 seconds.
My goal is to find the source code that implements AD9361’s tuning function in
the UHD source code so that I can comment out the calibration part to speed up
the frequency tuning.
The following source code files are related to AD9361 tuning:
* the set_tx_frequency() implemented in
`uhd/host/lib/usrp/dboard/e3xx/e3xx_radio_control_impl.cpp`
* the tune method in line 227 in the above figure calls the tune() function in:
`uhd/host/lib/usrp/dboard/e3xx/e3xx_ad9361_iface.cpp`
**Notice that the original source code is “catalina_tune” and I changed it to
“tune” because my experiments showed “tune” is much faster than
“catalina_tune”.**
* Finally, I find the tune() function above seems to call the tune() function
in: `uhd/host/lib/usrp/common/ad9361_driver/ad9361_device.cpp`
I find in line 85 AD9361_CAL_VALID_WINDOW is defaulted to 100 MHz and I change
the 100 MHz to 1 GHz. But nothing seems to change, the device still do a
calibration every 100 MHz.
I also comment out the calibration code in
`uhd/host/lib/usrp/common/ad9361_driver/ad9361_device.cppb`, but still nothing
seems to be changed. The device is still doing calibration every 100 MHz.
**Anyone knows where the source code for tuning ad9361 with E312 device is ? I
wish I can locate the tuning source code so that I can change it to speed up
frequency tuning.** In my application, if I can turn off the calibration that
happens every 100MHz, then the total tuning time is only 8 seconds, which is
just what I need. But I can not locate the true tuning source code.
Thanks,
Yan
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