Synchronize SPI clock with generated timer clock

[49bwjf8]

I am working with a IC that requires SPI clocks to be synchronized (in phase) with its system clock. Currently the IC's clock source is connected to one of the nRF52's GPIO pins which is driven by Timer 1, generating a 1MHz clock. SPI 1 is connected to the IC as a master and is configured with a frequency of 1MHz.

Currently while scoping both clock signals they are sometimes in-phase and sometimes out-of-phase. Is there any way for me to guarantee that when the SPI clock starts, its edges will be aligned with the timer output?

[ovrebekk]

Hi

You probably need to start the SPI interface in sync with the 1MHz clock put out by Timer 1. This should be possible by connecting the START task of the SPI peripheral to the compare event generated by timer 1 over PPI. 

Can you let me know which SDK version you are using, and which driver you are using for the SPI?

Best regards
Torbjørn

[49bwjf8]

Thanks for your reply! I am using nRF5 SDK v15.3.0 and am using nrf_drv_spi.

Is the time between starting the SPI peripheral and the rising edge of the clock deterministic?

[ovrebekk]

Hi

According to the SPIM electrical specification this delay is 1us typical. 

There are no min and max values unfortunately. I don't see any reason why it would be non deterministic, but I would recommend doing some testing to verify this. 

Best regards
Torbjørn

[49bwjf8]

Will do, thank you.

[ovrebekk]

The best of luck

Unless you have more questions I will consider the case closed.