On Fri, 3 Nov 2017 04:12:44 +0100 "Enrico Weigelt, metux IT consult" <info@xxxxxxxxx> wrote: > Hi folks, > > i'm currently developing an iio driver for a custom adc and looking > for the optimal approach > The device is made up of 3x 24bit-SD-ADCs and a fpga (as > buffer+bridge) connected via EIM. All ADCs operate at the same > (configurable, up to 500khz) sampling rate and each have their own hw > buffer. For each buffer there's a separate interrupt line. I assume we are talking a hw fifo? I'm going to guess with a watershed interrupt... > > So, i'd need an irq handler, which fetches the data into a suitable > buffer and push it into iio. is that what iio_triggered_buffer_setup() > etc is for ? How does that relate to triggers ? Triggers are used when you have a single interrupt for each sample pass of a given ADC. (a so called scan - of data captured at the same time - or often based on an internal shared sequencer). So typically when you have a flow involving a hardware buffer you skip the trigger and have the interrupt controller push data directly to the buffers from the interrupt handler thread. If you have 3 different interrupts and the ADCs have separate buffers then you can't guarantee to do reads from all on a single interrupt? (they can be sampled such that a single end of scan interrupt makes no sense?) In that case, as far as IIO is concerned you have 3 separate ADC systems which will need to each be a separate IIO device. You will then need some mfd type device underneath to handle the shared elements (such as the sampling frequency). We do support direct use of hardware fifo's but it almost always makes sense to buffer them through a software fifo as well. There is also infrastructure to match the fifo watershed with the software one so that you only read from the hardware when you want to read it from userspace. Jonathan > > thx > -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
