On Wed, Mar 30, 2016 at 10:25 PM, Slichter, Daniel H. (Fed) <daniel.slich...@nist.gov> wrote: > Now, as you suggest we could just change the level at which we make this > break from the AMC card, shift the DACs and ADCs onto the daughter card as > well, and use FMC to communicate with the whole thing. This makes it a bit > more expensive/difficult to reconfigure the analog front end, but the DAC and > ADC costs are not so high that it is impossible to do. I had envisioned the > notion of making the daughtercards simple enough that end users could > redesign/respin easily to accommodate their own applications, or we could > ship unstuffed or partially stuffed boards that they could complete with the > particular filters etc they desire.
It makes letting unused mezzanines collect dust on the shelf more expensive. > However, I agree that there are compelling arguments for using the > architecture you propose. We would need to pick just a few board styles (I > suggest quad DAC, 2 DAC/2 ADC, and quad ADC), and for each of these board > styles we would need to make several different variants with different analog > front ends (3 types for DAC - low frequency, baseband RF, upconverted RF - > and 2 types for ADC - baseband RF and downconverted RF, both likely including > switchable gain). So now we are looking at making 3 types of quad DAC > boards, 2 types of ADC board, and probably 3 types of DAC/ADC board > (upconvert DAC/downconvert ADC, baseband RF DAC/baseband RF ADC, and low > frequency DAC/baseband RF ADC). So now there are 8 different daughterboard > designs. If we restrict ourselves to just quad DAC or quad ADC on a given > daughtercard, then there are 5 designs, same as in the current proposal for > analog-only daughtercards. I would still want to have boards be partially > stuffed (or stuffed in different configurations on demand) to allow users to > choose the frequencies of interest for analog filters etc. > > If we proceed this way, we will need an external clock SMA for each FMC > module, because we don't want the high-quality external clock going down one > FMC connector, across the AMC, and up the other FMC connector for signal > integrity/crosstalk reasons. For a digital clock with fast edges 60 dB of crosstalk is _much_ less of a problem. > Are we thinking we would try to implement the actual VITA 57 standard on > these connectors? Or just use them as convenient high-speed-capable > connectors? I agree with the second idea, but I don't like the first one. What from the VITA 57 pin assignmend do you not like? Robert. _______________________________________________ ARTIQ mailing list https://ssl.serverraum.org/lists/listinfo/artiq
