ATMega32U4 Strange Looking Clock and MOSI Signals when doing ISP

[bendras]

I am seeing strange signals when trying to program ATMega32U4 with an ISP programmer (https://www.sparkfun.com/products/9825 to be more precise).



Anybody has any ideas on what might be causing such a stepped signal?


If I measure the clock signal which comes out of the ISP when its not connected to the ATMega32U4 board then it looks correct:

[Rerouter]

Its defiantly not transmission line effects, At a guess its a contested pin, What else connects to that pin on your circuit?

E.g. one device is pulling or driving high, and the other is trying to drive low.

[Gibson486]

Looks like you have another output or input pulling it down
 One cause could be multiple push pull outputs on the same line.

[bendras]

Thank you for the tips  .  It turned out that the MOSI and CLOCK pins on the ATMega32U4 IC where accidentally shorted while soldering  . After removing the solder bridge everything works as expected.