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1-32khz sensor-sampling loop

Nathan T <nathan@...>
 

hi all,

i'd like to sample a sensor (actually several sensors) in precise intervals at speeds up to 32khz.

it seems timer and sleep functions only have millisecond resolution and I cannot busy wait.

anyone have suggestions on the best way to go about this? 

best,
nathan
Michael Hope
 

Hi Nathan.  I'm fairly new to Zephyr, but if you're looking for hard real time-ish at 32 kHz then I'd talk straight to the hardware.

For example, say I needed to read an ADC channel at 32 kHz on the ATSAMD21.  I'd use the Zephyr drivers to initialise the ADC and DMA units and then do custom iniitalisation that:

- Sets up a 32 kHz hardware timer
- Uses the SAM0 event system to hook the timer into the ADC trigger
- Uses the SAM0 DMA unit to read the ADC and write to memory when the ADC conversion complete event triggers

The DMA can work in ping-pong mode and fire an interrupt when the buffer is half full.  This can then set a semaphore and wake up your task.

Hope that helps,

-- Michael


On Fri, 2 Feb 2018 at 17:36 Nathan T <nathan@...> wrote:
hi all,

i'd like to sample a sensor (actually several sensors) in precise intervals at speeds up to 32khz.

it seems timer and sleep functions only have millisecond resolution and I cannot busy wait.

anyone have suggestions on the best way to go about this? 

best,
nathan
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