Hi! Host CPU and TSC_ADC_SS have different clock domains. Internal ADC clock rate is 24 MHz. The theoretical maximum sample rate is 1.6 Msamples/s (= 15 cycles@24MHz in single shot mode) or 1.74 Msamples/s (= 14 cycles in continous mode). In praxis it's 200 ksamples/s.
The PRUSS are first choise for real time tasks with high timing accuracy. Below 10 ksamples/s the CPU latency (due to Linux non-real-time-ness) is small (less than 10 % on a vanilla system). When you need concrete hints, you'll have to specify your timing requirements: - Is the external clock a regular pulse train? - What frequency? - Which maximum latency is required between clock pulse and ADC sample? BR Am Mittwoch, 12. August 2015 08:34:02 UTC+2 schrieb Valeria M.: > > Hi TJF, thanks for your reply! > I was hoping not to have to resort to use PRUs D: , for now the low > accuracy given by the ADC clock will have to do. (btw why 10 kHz accuracy? > it's caused by Linux non-real-time-ness? Otherwise ADC clock frequency > should be 1,6 MHz max right?) > > Other random question: I suppose that if I sync the BBB system clock to an > external clock the ADC's one won't be affected by it right? I mean they > have different time 'domain'. > > Corss-compiling I'll be able to debug my procject. > > Valeria > > Il giorno martedì 11 agosto 2015 21:45:09 UTC+2, TJF ha scritto: >> >> Hi Valeria! >> >> The FSM module in the TSC_ADC_SS can either get triggered by software or >> by an external hardware event (TIMER4-7 or PRU_ICSS pr1_host_intr0). See SRM >> chapter 12 <http://www.ti.com/lit/pdf/spruh73> for details. >> >> The best way how to synchronize with an external clock depends on the >> clock frequency and the timming accuracy requirements. For high accuracy or >> above ~10 KHz you may need customized software. >> >> But below that frequency you may be happy with a simple solution: The ADC >> operates at a fast sampling rate and the host CPU just reads the current >> value when the external clock fires. This is feasible with libpruio >> <http://beagleboard.org/project/libpruio/>. (You may see some latency >> when the host CPU is busy by any system interrupt.) >> >> BR >> >> BTW: Cross-compiling adds further problems. Why not compiling on the BBB? >> > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to beagleboard+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
