SPI problem

[scancool]

I want to connect 20 shift registers to a SPI BUS but after 10 shift register the CLK gets a lot of distortion plus the spi bus has a distance of 6 feet, is there any type of buffer the is not too small to solder that I can use, I'm running a 20Mhz clock.

 

[LTX71CM]

The SPI bus is running at 20MHz over six feet or your microcontroller is running at 20MHz and your SPI bus happens to span six feet?

 

[scancool]

The SPI bus is running at 20MHz over six feet or your microcontroller is running at 20MHz and your SPI bus happens to span six feet?

the SPI expand six feet, and the clock is pulsing at 100ns I slow it down but I have to make it faster and I can cause the signal gets distorted, any idea what type of buffer I can use or what I can use to make it a perfect square wave?

 

[LTX71CM]

What's your operating voltage?

The problem is speed, distance and fanout. Check your controller's datasheet for drive current and then check that against the shift register datasheet inputs.

Is everything mounted on a PCB, with wire? Any shielding involved? Any form of noise reduction?

This is for an LED sign I presume?

 

[scancool]

What's your operating voltage?

The problem is speed, distance and fanout. Check your controller's datasheet for drive current and then check that against the shift register datasheet inputs.

Is everything mounted on a PCB, with wire? Any shielding involved? Any form of noise reduction?

This is for an LED sign I presume?

everything is mounted on 6 PCBs, and is to drive LEDs, is there any type of buffer I can use to increase the clock signal ? the clock signal is 3.3V