LTC2949 GPIO heart beat waveform

Question

Hi, 
 Should the heart beat waveform be square waveform? 
 Below red line is the waveform we measured on GPIO5, the frequency is correct as 400kHz, but I'm not sure if the waveform is what should be expected.

mvrablic · Accepted Answer

The expected heartbeat waveform is 400kHz 12.5% duty cycle. Although frequency and duty cycle look good here, I'm not sure why the waveform doesn't look like a square wave. Can you check the probe compensation or length of wire used to get to the signal/GND?)

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LTC2949 GPIO heart beat waveform