https://github.com/AtoLrn/Store_MQTT/blob/4adea618683839d7468265c25723be84b9cb285f/STORE_MQTT/STORE_MQTT.ino#L299 Maybe this line have a huge delay inside and change the tickrate of the stepper OR not enough delay and too much tickrate for the driver
Store_MQTT/STORE_MQTT/STORE_MQTT.ino
Line 299 in 4adea61
Maybe this line have a huge delay inside and change the tickrate of the stepper OR not enough delay and too much tickrate for the driver