Hi Franco, The sync inputs are usually used to synchronise multiple boards. If you feed an lvttl signal into the sync input of the adc5g, it will emerge from the sync output of the yellow block. Usually people drive this signal with a pulse per second signal from a GPS, and use the resulting simulink signal to synchronise their logic.
Trying to sync 2 ADCs perfectly is a bit tricky though. Unless the adc5g interface has changed since I last used it (which is possible), every time you reprogram your board, the latency of the ADC samples arriving to simulink is liable to change and might not be the same for both ADC cards. I *think* that the sync signal follows the ADC data through the interface's FIFOs, which means you can compensate for some of this variable latency using this sync. However, I don't think you'll be able to get the alignment of ADC streams better than 16 ADC clocks (one FPGA clock). Usually this isn't a problem - a correlator can usually fix these small offsets in software after taking data, and they don't change once you start running your system. Personally, if you need perfect real-time alignment, I would consider injecting some test signal into both adcs and correlating their digital streams to measure their relative phase differences. Perhaps someone else has a better / different answer. I know people have worried about precision ADC synchronisation for other ADCs before, but I don't know what solutions have been proposed or implemented in the past. Cheers, Jack On Thu, 29 Jan 2015 10:19 pm Franco <francocuro...@gmail.com> wrote: > Hi CASPER community, > I'm working with ROACH 2 and I need to synchronize the two ADC so that > both take samples at the same instant of time. Does anybody know how can I > achieve this synchronization? > > I've noticed that that the Simulink block model for these ADCs (adc5g), > doesn't have the option of using them in interleave mode in the block > parameters, contrary to ROACH1 ADC blocks (adc_083000x2). > > I've also noticed that the ADC boards have a SYNC input, but I don't know > how to use it. > > Thanks, > Franco > > -- > Franco Curotto > Estudiante de Ingeniería Civil Eléctrica > Facultad de Ciencias Físicas y Matemáticas > Universidad de Chile >
