Hello, I'm trying to get feedback on whether our external SPI ADC sampling approach seems like it should work, or if it seems like there's a problem.
We're using an LPC55S69 and we're trying to sample continuously into DMA ping-pong buffers from an SPI ADC (the ADC is an ADS8860 SPI slave device, with SCLK, active-low framesync "convert strobe", data out, and 16-bit samples). The LPC55S69 and ADC is on a custom board and is connected to the Flexcomm8 High-Speed SPI peripheral. (But we also have LPC55S69 evaluation boards available for experimenting.)
We tried setting up CTIMER2 to generate Match0 events at our desired ADC sampling rate (and that works), and then we tried using DMA0 channel 2 (High Speed SPI Flexcomm8 RX) with trigger mux DMA0_ITRIG_INMUX2 set to the DMA0 trigger input value for CTIMER2 Match0, with TXIGNORE set to 1. That has not worked yet. So far, all we have managed to do is to clock one ADC sample into the LPC55S69 when using CTIMER2 Match0, or to clock in a whole buffer of samples, but at much too high a sampling rate when we don't pace the ADC sampling with CTIMER2 Match0.
Does our approach seem like it should work? Or is there a problem that we have missed?
We have succeeded in what seems like almost exactly the same approach with the onboard ADC continuously sampling into DMA ping-pong buffers, with the sampling rate controlled by CTIMER2 match0.
I'll try to post example code for the evaluation board soon. Thank you very much!
Jim
