Hi everyone,
I been extensively testing the adc_snap problem and I have not been able to
figure it out.
I am using a Rpi and adc0_clk (fclk=10 MHz, I was previously using 50 MHz)
and simplified to the minimum expression the diagram: ADC+ snap-block
- Results from testing the option of using 12 ADC with the configuration
[1,2,3,4], I get the pattern 1,1, 2,2, | 3,3, 4,4 when it should be
1,2,3,4, | 1,2,3,4 . Being {adc1, adc2, adc3, adc4}@t=0| {adc1, adc2,
adc3, adc4}@t=1
- Results from testing the option of using 6 ADC with the
configuration [1,1,3,3], I get the pattern 1,1,1,1 | 3, 3, 3, 3 when it
should be 1,1,3,3| 1,1,3,3. Being {adc1, adc2, adc3, adc4}@t=0| {adc1,
adc2, adc3, adc4}@t=1
- Results from testing the option of using 3 ADC with the
configuration [1,1,1,1] it works fine.
I tested all the ADC configuration possibilities, the ones that make sense
and even what does not make sens. I am very much convinced that this is not
an ADC miss-config.
QUESTIONS
- Any other idea/test that I could run to see what is the source of such
behavior?
- Anyone is using the SNAP in a 12 ADC or 6 ADC configuration? I am
guessing that a lot of people, but just to confirm it.
- Could you tell me what version of mlib_devel library are you using?
- What casperfpga library are you using ? (I updated the last casperfpga
library version with identical results)
Thank you,
XB
On Mon, Sep 9, 2019 at 1:35 PM Xavier Bosch <[email protected]>
wrote:
> Hi Jack
>
> I did multiple extra test, all of them with the same result: outputs are
> multiplexed in time.
> I am using casperfpga 284a4ba from
> https://github.com/ska-sa/casperfpga.git
>
> Thanks,
> XB
>
>
> On Fri, Sep 6, 2019 at 11:52 AM Jack Hickish <[email protected]>
> wrote:
>
>> Hi Xavier,
>>
>> The only yellow block info you'll find is by looking at the code. When
>> configured properly for a given mode, the block doesn't time multiplex
>> multiple ADC channels, it does what you expected it to do. I just
>> checked the init code we use for HERA, and it's pretty much the same
>> as you, though we use inputs 1 and 3 (adc.selectInput([1,1,3,3]). I'm
>> not sure if this is significant (I don't think it should be).
>> What version of casperfpga are you using?
>> Cheers
>> Jack
>>
>> On Wed, 4 Sep 2019 at 09:18, Xavier Bosch <[email protected]>
>> wrote:
>> >
>> > Hi all,
>> >
>> > I been using SNAP board (a regular-standard board) for a while now in a
>> 3-ADC @ 800 MHz configuration mode. I would like to use it in a 6-ADC @
>> 500 MHz configuration mode and I am having some trouble understanding what
>> is going on. I read the HMCAD1511 datasheet.
>> >
>> > ADC configuration with [1,1,2,2] (see the whole ADC calibration
>> function at the end of this email)
>> >
>> > I connected a snap block (dataloggers) to the yellow-block (snap_adc)
>> to record time series of the collected data. What I see is that ADC0 and
>> ADC1 outputs are not spitted between a0 and a1 (yellow block) and a2 and
>> a2, respectively.
>> > Instead, what I find is that they are time multiplexed, ie. at t0 I
>> have that ADC0 is at a0, a1, a2 and a4, and at t1 I have ADC1 at a0, a1,
>> a2 and a4
>> >
>> > See attached picture of 8 consecutive samples of a0, a1, a2 and a3 with
>> only ADC0 connected (figure ADC0_ch0) and then ADC0 and ADC1 connected
>> (Figure_ch0_ch1), ie. First row is t0, second row is t1)
>> >
>> > The HMCAD1511 datasheet does not show a time multiplexed output but a
>> parallel output. I do not know how the yellow block is implemented. Where I
>> could find more information about the yellow block implementation?
>> > Is that the expected yellow block output? If the yellow block time
>> multiplexes the ADC0 and ADC1 then how do you synchronize the channels with
>> the rest of the design?
>> >
>> >
>> > code that I use to configure/calibrate the ADCs
>> >
>> > def init_adc(self):
>> >
>> > self.sample_rate=500
>> >
>> > adc = casperfpga.snapadc.SNAPADC(self.fpga,ref=50)
>> >
>> > if adc.init(self.sample_rate, numChannel=2,resolution=8) == 0:
>> >
>> > print "ADC calibrated! "
>> >
>> > else:
>> >
>> > print "ERROR ->>> ADC NOT calibrated! "
>> > sys.exit(0)
>> >
>> > #adc.selectADC(0)
>> >
>> > adc.adc.selectInput([1,1,2,2])
>> >
>> >
>> >
>> > Best,
>> >
>> > XB
>> >
>> >
>> >
>> >
>> >
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