[quote userid="652050" url="~/support/microcontrollers/arm-based-microcontrollers-group/arm-based-microcontrollers/f/arm-based-microcontrollers-forum/1506319/am2432-use-general-ecaps-to-generate-a-clock-signal-for-delta-sigma/5792547#5792547"]However if i apply a constant current to the shunt resisotr the aquired (raw) sample values change (drastically) if i change the ChannelX SDFM Clock (Hz). How is this possible (Theoretically with a constant current this value should have no effect)? [/quote] In ICSS PRU, Sigma-Delta Sinc filtering is achieved through a combination of PRU hardware and firmware. The PRU hardware provides hardware integrators that perform the accumulation part of the Sinc filtering, while the differentiation part is handled in the firmware. As mentioned, the ChannelX SDFM Clock (Hz) value is used to configure the IEP CMP4 event, which is responsible for sampling timing. The firmware reads the accumulator output when the CMP4 event is triggered. If you see the doc, the CMP event get updated for the next sample after every time. This update depends on the Sigma-Delta clock, OSR, and Sinc filter parameters. If you change the Sigma-Delta clock value, the firmware will read accumulator output at different times, causing a mismatch where the accumulator buffer has values of different OSR , and the differentiation buffer also has values for different OSR (desired OSR). This will lead to an issue where the accumulation and differentiation OSR for the same sample data will not align Thanks & Regards, Achala Ram
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