How to generate short reset pulse using nRF9160 DK.

[Juha]

I have some module chip connected to the nRF9160 DK providing the sensor data over I2C line. In some state transition of the module the short reset pulse needs to be generated to GPIO line. Max allowed pulse length is 45 ns. Is this possible with nRF9160 and what is the best way to do it? Any code examples generate the short pulse?

[haakonsh]

That's going to be a bit tricky as our peripherals run on a 16MHz clock (62.5ns). You'll have to create the pulse with an external transistor or two, and some kind of RC circuit for timing the pulse width.  

[Juha]

I was trying to use registers directly, but of cause I would need some ns delay function. Is there any ns wait function implemented with C or any asm wait examples? The problem might still be the line is not pull down fast enough in 45ns period.

NRF_P0_NS->OUTCLR = (1UL << RESET_PIN);
NRF_P0_NS->OUTSET = (1UL << RESET_PIN);     

[haakonsh]

The GPIO peripheral is synchronized with the 16MHz AHB bus. The shortest pulse width that you can generate is 62.5ns. 

Is the reset signal active high or low?
What is 'V input high' and 'V input low' for the reset signal? 

You might be able to create a shorter pulse with just an external capacitor, depending on the specifications of the reset signal.

[Juha]

There was typo in the specification and also pulse length was wrong. So no more issue with this.

[haakonsh]

I'm glad to hear you've solved the issue, can I ask what device it was?