PPI + SPI + Timer.

[irina_gabriela]

Hi guys. I'm fairly new at embedded development and I'm basically trying to set up a workflow that goes like this:

1. Toggle a GPIO high - low, with a duty cycle of ~500 nS.
2. Enable the SPI peripheral
3. Get 16 bits
4. Disable the SPI peripheral
5. Sleep until next event.

The frequency of these events should be 16 kHz. So basically I'd need to get 16 kSamples @ 16bit / sample. With the added complexity of a softdevice peripheral. I'd like to keep the interrupts at a minimum.

Should I use PPI or a PWM library? I'd really like to keep the CPU intervention to a minimum, as to burn as little power as humanly [microcontrollerly] possible.

[Einar Thorsrud]

Hi,

It looks to me like the GPIO here is the slave select / chip select. The SPIM hardware does not have support for chip select, but it is supported by the driver. So if you are happy with the timing there, you can get this for free from the SPI driver. If not and you need exact timing, then using GPIOTE and a TIME via PPI is the way to go. For that I suggest you refer to the PPI example (assuming you use the nRF5 SDK). I do not see a reason to use PWM here.

Einar