1uS serial waveform construction at 3.3V

[SRall]

Hello!

I am trying to interface with some old hardware that communicates over a single data pin. I need to take in varying 32-bit packets and output the data that translates each bit into a specific 1uS-base waveform. E.g. 0 = 3uS Low + 1uS High ; 1 = 1uS Low + 3uS High. This is needs to be at 3.3V logic. 

My question is on approach to this (assuming this is possible), I'm not totally experienced in using the hardware peripherals for the latest nRF52 chips but I do have a few 840 DKs to test with. Should I go about this using PWM? Or should I construct this solution using GPIOTE and PPI timers? Some other peripheral that would work well here?

I'm poking around the pwm and gpiote examples in SDK 16 as I come up with a solution but thought I'd post here to see if there was as better way than what I come up with. 

Many thanks in advance!

Sam

[Dmitry]

You're watching your signal at 4kHz sampling rate, to see 1Mbps signal, you need at least 2MHz sampling rate. Also, NRF_DRV_SPI_DEFAULT_CONFIG has 4Mbps default settings, you need to set spi_config.frequency = NRF_DRV_SPI_FREQ_1M for 1Mbps.

[SRall]

Hey good catch Dmitry. After adjusting the sample rate I can start to see some recognizable pulses, and I've managed to construct an appropriate waveform, however the data are still far apart from each other, what do I need to change in order to control the delay after my data has been transferred?

[Dmitry]

Hi Sam,

did you have success with your waveform?

[SRall]

Yes! Per your suggestion I was able to construct my required waveform with a proper SPI implementation at the right clock speed. Much thanks!