Hi, Eric On Wed, Jun 17, 2009 at 1:52 AM, Eric Blossom <e...@comsec.com> wrote:
> On Tue, Jun 16, 2009 at 09:15:34PM +0800, Su Jinzhao wrote: > > Hi, > > > > I want to read RSSI value using analog AUX ADC, I think we can read RSSI > > through AUX_ADC_A1 pin of AD9862, I looked through the code > > of usrp_read_aux_adc in file > > /root/gnuradio/gnuradio-3.1.3/usrp/host/lib/legacy/usrp_primes.cc, > > If you are using usrp_standard_rx, or gr.usrp_source_*, you can do > this much more simply by using: > > adc_val = u->read_aux_adc(which_side, which_adc) > > http://gnuradio.org/doc/doxygen/classusrp__basic__rx.html > http://gnuradio.org/doc/doxygen/classusrp__standard__rx.html > > You didn't mention which daughterboard you are using. Not all > daughterboards have an analog RSSI output. > my question is: > 1.The AD 9862 specification says: "The AUX SPI can be enabled and configured > by setting register AUX ADC CTRL. Setting register use pins high enables the > AUX SPI port.", but in the above code AUX_ADC_CTRL_AUX_SPI was not set high( > In my opinion, aux_adc_control should be added with | = AUX_ADC_CTRL_AUX_SPI > because usrp_9862_write and usrp_9862_read all need SPI operation, so we > should enable AUX API), Is this a mistype or another method ? The code is correct. There are a couple of ways to use the AUX ADCs. > We use them by polling, not over the AUX SPI bus. > > > 2.stefan.bruens in the list had said that the low 16 bits is the RSSI > value, > > I want to know why did the above code combine the high and low 16-bit and > > format the data into 12-bit ? > > This is a digital RSSI, determined post high-speed ADC. You can look > at the computation here: > > http://gnuradio.org/trac/browser/gnuradio/trunk/usrp/fpga/sdr_lib/rssi.v > > > > 3. Even with the RSSI value (int type), what should I do to convert that > > value into dBm unit ? > > You would need to calibrate the entire signal path. Left as an exercise... > > Eric > my new questions are (Sorry for my talkactive ^_^ ) : 1. Autually, I was indeed use u->read_aux_adc(which_side, which_adc) in my python code, However, I can't step into the C++ code while using pdb to debug my python code, so I am not sure whether read_aux_adc() really call the function usrp_read_aux_adc in file gnuradio-3.1.3/usrp/host/lib/legacy/usrp_prims.cc ? 2. In the function usrp_read_aux_adc, we can read values of registers 26-33 directly, so I am confused with the relation between usrp_read_aux_adc and the rssi.v code, do they have no relation ? 3. If I want to convert the RSSI value into dBm units, means that I have to find the reference voltage and resistance,( however, on page 16 and 30 of AD9860_9862 specification, settings of bits Refsel B/A are illustated self-contradictory), and then calculate the power with voltage and resistance ? Please confirm me whether my idea is correct. 4. By the way, I am using daughterboard RFX2400 and RFX900, so I think this two daughterboards have no problem with RSSI output. -- Su Jinzhao
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