connecting an ultrasonic distance sensor to nRF52

[Sampo]

Hello,

Have been reading the example codes and documentation in order to connect an ultrasonic sensor to nRF52. The goal is to read in the value and then send it over BT to a mobile.

So I'll need a soft device running. Basically the usage of the sensor is very simple. I trigger it to do the measurement, by pulling up a GPIO pin for 10us and the sensor will report the distance as pulse to the input pin. The width of this pulse equals to the time the ultrasonic pulse needs to travel back and forth, between the sensor and the object to be recognized. This means that I need to be able to measure the width of the pulse with accurancy of say +/- few dozen us. I can do this easily with gpiote framework and creating an object that statically stores the timestamp for high and low edges of the pulse... But the question remains; How to make this work well together with the softdevice? Please advice.

Best Regards, Sampo

[Matt]

So your sensor cannot return an analog output value? You can still use gpio and saadc even with softdevice present in the nRF52.

[Sampo]

Unfortunately no. No analog out put. I agree with you, have used in past on nRf51 the adc at 200Hz and BTLE sending at rate of 100Hz and it works perfectly. But now I would need to measure the width of the pulse. Does PPI or GPIOTE tasks offer any help here?

[Sampo]

To be more precise here, can I set up an input pin to generate separate events on hi-to-low and low-to-hi? I mean I can set it to generate an event on toggle, but if I would have separate events, I could create a timer that would be started on low-to-hi and stopped on hi-to-low by PPI, right? Then I could just trigger the sensor to measure distance, wait for a while and then read the timer value as PPI would have done it's magic behind the scenes?

[ovrebekk]

Hi

If you use two separate GPIOTE channels you can get separate events for low-to-high and high-to-low.

Just configure them to use the same GPIO, and give them different polarity.

Best regards