Hi Nilan, You'd need to look at the interface firmware to see exactly how the clock is generated on the FPGA, but essentially, yes, the 240 mhz clock is derived by dividing down the clock the ADC chip passes to the FPGA (which may or may not be equal to the sampling rate, depending on the exact setup).
On roach 2, there's all kinds of irritating constraints on the way that clocks can be multiplied up and divided down, which lead to the limitations described here - https://casper.berkeley.edu/wiki/ADC16x250-8#ADC16_Sample_Rate_vs_Virtex-6_MMCM_Limitations So you won't hit a "maximum" frequency issue as such, but there are only certain windows of sample rates which work. Hope that helps J On Wed, 9 Mar 2016, 13:03 Nilan Udayanga, <[email protected]> wrote: > Hi All, > > Thank you very much for all your suggestions. > > I have two more questions, > > Since, ADCs need to be clocked at 480 MHz for the demux=2 mode, how does > the FPGA clock at 240 MHz? does it use a clock divider internally? > > Is there any maximum operating frequency for the FPGA, when we use the > adc16 block? > > Regards, > Nilan Udayanga. > > On Wed, Mar 9, 2016 at 3:22 PM, Jack Hickish <[email protected]> > wrote: > >> With regards to the demux option, for the system you describe you want -d >> 2 (I.e. demux by = run the FPGA at half the sample rate, and process two >> samples in parallel on every FPGA clock cycle). Basically, provided you >> have the up to date ruby package, all you need to do is run adc16_init.rb >> with appropriate options, and that will program your roach and set >> everything up for you. >> >> I think the default mode of the adc16 ruby script assumes that, whatever >> mode you're using the ADC in, the external clock provided is at the sample >> rate. Though, as Matt added, the ADC supports other dividing options if >> they're useful to you and you're willing to read the ADC data sheet to work >> out how to set the divider properties. >> >> Cheers >> Jack >> >> >> On Wed, 9 Mar 2016, 09:49 David MacMahon, <[email protected]> >> wrote: >> >>> Hi Vishwa, >>> >>> I am not at my computer right now, so this is from memory, but I think >>> you want to specify an IP clock rate of 240 MHz and supply a 480 MHz clock >>> to the ADC card(s). The IP clock rate is sometimes called the fabric clock >>> rate. It is the rate at which the FPGA logic elements (aka fabric) operate. >>> The ADC chips need a sample clock that is commensurate with the sampling >>> frequency. When you initialize the ADCs using adc16_init.rb, be sure to >>> pass the "-d" option. If your version of adc16_init.rb does not support the >>> "-d" option, then you will need to update it. >>> >>> Hope this helps, >>> Dave >>> >>> On Mar 9, 2016, at 08:33, Vishwa Seneviratne <[email protected]> >>> wrote: >>> >>> Hi David/Jack, >>> >>> We are working on a beam former and we use the 'ADC16x250-8 coax rev 2' >>> to sample RF signals using ROACH2-Rev 2. The operating BW is 240MHz. Thus, >>> we need to sample the signals at 480 MSamples/s. We have few queries >>> regarding the adc16 yellow block and how to setup the input clock. >>> >>> 1. Can we compile a design by setting the IP clock rate to 480MHz? >>> 2. Should we supply a IP clock frequency of 480MHz to the ADC board to >>> achieve a sampling rate of 480MSamples/s. If not, at what clock rate >>> should we supply? And what other parameters needed to setup when running >>> the bof file. >>> >>> Thank you >>> >>> >>> Sincerely, >>> >>> >>> *Vishwa Seneviratne* >>> >>> *Graduate Student* >>> >>> *Dept. of Electrical and Computer Engineering* >>> *University of Akron* >>> >>> On Wed, Feb 3, 2016 at 12:38 PM, David MacMahon < >>> [email protected]> wrote: >>> >>>> Hi, Vishwa, >>>> >>>> The software installed by following the ADC16 user guide had not been >>>> updated with the newer version of the adc16 code that supports demux mode. >>>> I have updated the software that the user guide points to, so if you >>>> reinstall the adc16 gem as per the user guide you should get version 0.4.0 >>>> which supports demux mode. >>>> >>>> Thanks for bringing this issue to my attention. >>>> >>>> Dave >>>> >>>> On Feb 3, 2016, at 7:02 PM, Vishwa Seneviratne <[email protected]> >>>> wrote: >>>> >>>> Hi Dave, >>>> >>>> Here is the output. >>>> >>>> vishwa@server3:~/Desktop/roach/poly$ adc16_init.rb -h >>>> Usage: adc16_init.rb [OPTIONS] HOSTNAME BOF >>>> >>>> Programs HOSTNAME with ADC16-based design BOF and then calibrates >>>> the serdes receivers. >>>> >>>> Options: >>>> -i, --iters=N Number of snaps per tap [1] >>>> -r, --reg=R1=V1[,R2=V2...] Register addr=value pairs to set >>>> -v, --[no-]verbose Display more info [false] >>>> -h, --help Show this message >>>> >>>> >>>> vishwa@server3:~/Desktop/roach/poly$ gem list adc16 >>>> >>>> *** LOCAL GEMS *** >>>> >>>> adc16 (0.3.6) >>>> >>>> >>>> >>>> >>>> Sincerely, >>>> >>>> >>>> *Vishwa Seneviratne* >>>> >>>> *Graduate Student* >>>> >>>> *Dept. of Electrical and Computer Engineering* >>>> *University of Akron* >>>> >>>> On Wed, Feb 3, 2016 at 11:28 AM, David MacMahon < >>>> [email protected]> wrote: >>>> >>>>> What does "adc16_init.rb -h" show? What does "gem list adc16" show? >>>>> Maybe you need a newer version of the adc16 code. >>>>> >>>>> Dave >>>>> >>>>> On Feb 3, 2016, at 18:20, Vishwa Seneviratne <[email protected]> >>>>> wrote: >>>>> >>>>> Hi Jack, >>>>> >>>>> I'm thinking that the ruby script 'adc16_init.rb' does not identify >>>>> the '--demux' parameter. I used the code at 'git:// >>>>> github.com/david-macmahon/casper_adc16.git'. What can I do to set the >>>>> parameter? >>>>> >>>>> Thank you >>>>> >>>>> >>>>> Sincerely, >>>>> >>>>> >>>>> *Vishwa Seneviratne* >>>>> >>>>> *Graduate Student* >>>>> >>>>> *Dept. of Electrical and Computer Engineering* >>>>> *University of Akron* >>>>> >>>>> On Wed, Feb 3, 2016 at 11:02 AM, Vishwa Seneviratne < >>>>> [email protected]> wrote: >>>>> >>>>>> Hi Jack, >>>>>> >>>>>> I did try all the combinations. The error remains the same. >>>>>> >>>>>> $ adc16_init.rb -v --demux=1 192.168.10.5 poly_design.bof >>>>>> /var/lib/gems/1.9.1/gems/adc16-0.3.6/bin/adc16_init.rb:40:in `<top >>>>>> (required)>': invalid option: --demux=2 (OptionParser::InvalidOption) >>>>>> from /usr/local/bin/adc16_init.rb:19:in `load' >>>>>> from /usr/local/bin/adc16_init.rb:19:in `<main>' >>>>>> >>>>>> >>>>>> Sincerely, >>>>>> >>>>>> >>>>>> *Vishwa Seneviratne* >>>>>> >>>>>> *Graduate Student* >>>>>> >>>>>> *Dept. of Electrical and Computer Engineering* >>>>>> *University of Akron* >>>>>> >>>>>> On Wed, Feb 3, 2016 at 2:25 AM, Jack Hickish <[email protected]> >>>>>> wrote: >>>>>> >>>>>>> Hi Vishwa, >>>>>>> >>>>>>> Is the syntax definitely -demux=1 andnot either --demux=1 or -d 1 ? >>>>>>> >>>>>>> >>>>>>> Jack >>>>>>> >>>>>>> On Wed, 3 Feb 2016, 12:39 a.m. Vishwa Seneviratne < >>>>>>> [email protected]> wrote: >>>>>>> >>>>>>>> Hi, >>>>>>>> >>>>>>>> I am working on how to work with different operating of >>>>>>>> the 'ADC16x250-8 coax rev 2' for a very simple design to test how the >>>>>>>> ADC >>>>>>>> works. The design is compiled at an IP clock rate setting of 200MHz. My >>>>>>>> objective is to sample my input signal at higher sampling rate >>>>>>>> (preferably >>>>>>>> 400, 800 MHz). >>>>>>>> >>>>>>>> According to the user guide '' >>>>>>>> https://casper.berkeley.edu/wiki/images/4/4c/ADC16_user_guide.txt"; >>>>>>>> by setting the demux parameter I should be able to switch between >>>>>>>> different >>>>>>>> sampling rates. I get the following error. >>>>>>>> >>>>>>>> $ adc16_init.rb -v -demux=1 192.168.10.5 poly_design.bof >>>>>>>> /var/lib/gems/1.9.1/gems/adc16-0.3.6/bin/adc16_init.rb:40:in `<top >>>>>>>> (required)>': invalid option: -demux=2 (OptionParser::InvalidOption) >>>>>>>> from /usr/local/bin/adc16_init.rb:19:in `load' >>>>>>>> from /usr/local/bin/adc16_init.rb:19:in `<main>' >>>>>>>> >>>>>>>> When I don't pass the 'demux' parameter the ADC board get >>>>>>>> initialized to 8 analog inputs by default. >>>>>>>> >>>>>>>> How do I resolve this issue? or how can I set the ADC's to operate >>>>>>>> at different sampling rates? >>>>>>>> >>>>>>>> Thank you in advance >>>>>>>> >>>>>>>> Sincerely, >>>>>>>> >>>>>>>> >>>>>>>> *Vishwa Seneviratne* >>>>>>>> >>>>>>>> *Graduate Student* >>>>>>>> >>>>>>>> *Dept. of Electrical and Computer Engineering* >>>>>>>> *University of Akron* >>>>>>>> >>>>>>> >>>>>> >>>>> >>>> >>>> >>> >
