Rise time of SPI Signal

[hossam]

Posted on February 10, 2015 at 10:50

Hi

I am using STM32F103

RBT6

@72MHZ I use SPI with DMA to stream data from memory to GPIO SPI Prescaler is 4 GPIO is configured as output push-pull and speed 50MHz The problem is that the data output rise and fall time is very slow, instead of getting square wave out of the scope for 0xAA data I get sine wave ''snapshot attached'' How I can get square wave with good rise and fall time at this frequency? Salam Hossam Alzmor #gpio-risetime

[AvaTar]

Posted on February 10, 2015 at 12:26

This is not a problem of GPIO initialisation (this MHz value is only for glitch filtering), but of your PCB layout.

More exactly, the

https://en.wikipedia.org/wiki/Characteristic_impedance

of your slave connection.