SPI not operating correctly at high speeds

[T IJ]

Hello,

I'm having issues getting my SPI to work at high transfer speeds.
I have my pins configured to have high drive.

SPI is set to MSB first, Mode 0. 

Colors:

Brown = SCK

Red = MOSI

Orange = MISO

Yellow = CS

This is a transaction on 125kbps, working  fine.

This is at 500kbps, not getting all clock pulses.

This is at 8Mbps and yeah... nothing here but the chip select.

Can anyone help me getting this work at higher speeds?

Kind regards.

[Simonr]

Hi

Seeing issues at 500kbps already seems very strange, as that doesn't really qualify as "high-speed". What pins exactly are you using for SPI here? Is your project based on one of our example projects? If not, please check one of our SPI example projects, whether you're able to reproduce this issue there as well.

Best regards,

Simon

[T IJ]

I've used the example project and changed the pins to:

spi_config.ss_pin = 25;
spi_config.miso_pin = 11;
spi_config.mosi_pin = 19;
spi_config.sck_pin = 7;

[T IJ]

I've done some further measurements and found out that the SCK signal isn't looking that good.

This is done using 50Msps analyzer and the Vmin and Vmax are not what I expect them to be.

 

This is what the data looks like and here the Vmin and Vmax are what I expect them to be.

Anyone got a clue what is going on?

[Simonr]

Are you able to reproduce this on a DK, or are you only seeing this on a custom board? If this is specific to a custom board, please check your soldering, as the SCK pin may be connected somewhere it shouldn't be, or the other way around. All the pins you're using should be okay, and if that's the only thing that has changed in your project code, everything points toward this being a HW issue.

Best regards,

Simon

[T IJ]

I am testing it like this, without any external device attached to it.

Please tell me its a hardware issue