Re: [Discuss-gnuradio] bug with gain setting in usrp1?

[Wolfgang Buesser]

Hmm,

I don't think so:

What I apply to board A ADC0 shows up on scope0, and what I apply to board A 
ADC1 shows up on scope1, so there are definitely two different ADCs involved.
Looking at the scope traces they are connected as set by the line 
self.uhd_usrp_source_0.set_subdev_spec("A:A A:B", 0) 
i.e:
DDC-channel0, input I from board A, ADC0
DDC-channel0, input I from board A, ADC1

Both Q-inputs to GND

It appears, that the gain settings are somehow skewed up.
I am sure that the gain for both ADCs attached to same LFRX-board got be set 
individually.
Do I need a special FPGA code?



Wolfgang

>Those are two DDC channels, derived from the same physical, analog, hardware 
>and ADC.
>
>
>The LFRX itself has no gain-setting device, but the ADC does, so when you set 
>the gain on the ADC, you're setting the gain for both DDC-derived channels.
 
 
>>on May 29, 2013, Wolfgang Buesser >><address@hidden> wrote:
>>Hi,
>>        I am having problems with the gain-settings on the RX-channels of 
>> usrp1
>>        My USRP1 is populated with 2 LFRX and 2 LFTX.
>>        
>>        I want to use 2 DDC-channels each connect to one 2 ADC of LF-RX-Board 
>> A.
>>        I have generated the following code with grc.
>>        
>>        When apply a signal of roughly 11MHz I see the mixed signals on each 
>> scope.
>>        The relation to the inputs is o.k.
>>        
>>        The gain-settings are however not as I expect:
>>        self.uhd_usrp_source_0.set_gain(6, 1) affects both channels while 
>> self.uhd_usrp_source_0.set_gain(6, 0 has no effect.
>>        
>>        From what I rememeber that was different in the pre-uhd-times.
>>        
>>        Any hint, on how I can set the gains for both channels independently?
>>        
>>        Thanks
>>        
>>        Wolfgang