mosi output confusion when the speed less 5 tick.

[min_yuan]

Hi there,

I'm working on nrf52832 and using a PPI channel between a Timer and an SPI to output a voltage, for now, it works fine. But when I try to make it faster, e.g every 4 clock tick at 16Mhz timer send a byte by SPI, the pulse in the digital oscilloscope it wrong, but if change the clock to 5, the pulse is right.

fastest SPI speed is 5 clock tick(16Mhz timer)? as the documentation said, it should be 8Mhz, is there something I miss?

[Jørgen Holmefjord]

Hi,

You will need to wait for the SPI transfer to finish before starting a new one. The transfer time of one byte will be more than 5 tick on the 16 MHz timer when you run SPI on 8 MHz. There may also be some overhead on starting/stopping a transfer in the HW peripheral, see this post.

Best regards,
Jørgen