Can nRF52840 SPIM speed be 8MHz with 1.8V power supply?

[pjm]

How to make the nRF52840 SPI work in 8M with 1.8V supply?

We test the PCA10056 nRF52840 DK board, and find the 8M SPI CLK&DATA wave is very bad. The 8M SPI works fail with 1.8V power supply.

My question:

1. Could the nRF52832 and nRF52840’s SPI supports 8M SPI with 1.8V power supply?
2. Are the following test figures normal on nRF52840 DK board?
3. Is there anyway to make the SPI working good with 8M SPI?

 

The following pictures are tested on nRF52840 DK board, with 3V power supply and example code from nRF5_SDK_16.0.0_98a08e2\examples\peripheral\spi

1. 8M SPI CLK, it’s very bad(The high voltage is not high enough, the low voltage is not low enough; no setup time and hold time.).

2. 4M SPI CLK, it’s a little better, but not enough.

3. 1M SPI CLK, it seems ok(with enough setup time and hold time).

After increase the GPIO drive strenth (H0H1), the waveform looks better, but is still not good enough.

  

[run_ar]

Hi,

Yes, SPIM should be usable at 1.8V but it's likely you will need to enable High drive strength. And also make sure you have reasonable short lines. If they are to long your rise/fall times will increase. You can see the rise/fall times in the GPIO spec here: GPIO Electrical Specification. Please also make sure you do not use any of the "Standard drive, low frequency I/O only" pins as described here: Pin assignments

[pjm]

Hi,

Thanks for your reply.

The pin assignment of SPI is as follow:

The GPIO P0.14\P0.22\P0.24 usement as follow pictures:

please help check whether the pin assignments is OK or not.

[run_ar]

Looks like you already checked. And Yes, these pins are ok to use for High speed protocols.