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Sine waves appearing at adc_data_i/q.  Why?

Question asked by ThomasCook on Nov 28, 2016
Latest reply on Apr 18, 2018 by tejas.bhumkar@gmail.com

Hello,


Working with FMCOMMS5 board and No-OS software. I am monitoring the ADC signals with ila blocks in Vivado so I can see the signal values (set as analog wavforms) for each adc_data_i path. When I step through the code, during the Digital tuning I see a PRBS signal (expected training sequence).  

 

But when everything is done (now in CLI routines) I see sinusoids at each adc_data_i0 and adc_data_i1 buse.  I am guessing that the AD9361-internal loopbacks are still present but I'm not sure.   Am I seeing the transmitted sine waves reflected back at the receiver?  What is the feedback path?   I'm wondering if the loopback is still present.  I see in the ad9361_conv.c file, within function ad9361_dig_tune at line 436 it appears to be turning off the loopback
ad9361_bist_loopback(phy, 0);   yet the signals are showing up at the adc busses.   


Also, I need to know how to turn on the analog switches U305 and U306 so I can control the board level loopback paths. The signals labeled gpio_cal_sw1 and gpio_cal_sw2 in the default initialization structure.  But I don't see a function that turns them on or off.  Is there an existing function to control the two switches?

 

Please advise.


Tom

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