What are your thoughts on how to correct this waveform? The pulse should be a 410 ns wide and 5 V high square wave.
The driver is a 74HCT365 push-pull buffer, supplied from the 5 V rail. The input (3.3 V from an ESP32) to the IC looks perfect.
There is approximately 25 feet of 3C16 cable (12 V, ground, signal) between the buffer and the input of the WS2815 LED strip.
The basic circuit is like this: ESP32->75HC2365->series resistor->connector->25' cable->LED strip. The waveform capture was taken at the connector.
I tried adding 20 μF of bulk capacitance across 5 V and GND about 2 mm from the buffer IC. I've also tried a ~400 Ω series resistor between the buffer and the WS2815. Neither significantly changes the output.
The LED strip functions properly, but this output is going to bother me if I don't clean it up.
Using the suggestion below I lowered the series resistor to ~50 &ohm.
Yellow is between the resistor and buffer. Blue is taken between the resistor and cable. Purple is between the cable and led.