How to update firmware for 20 teeth pulley?

I have purchased 20 teeth pulleys and don’t know how to update the firmware.
Anyone have done this?

You will need to update your steps per mm.

For 1.8 degree stepper motor with GT2 belt, and microstepping at 1/32 your steps per mm is 160.

It is located in your configuration.h file

Just a bit more detail. You will need to load the Arduino IDE and then load the firmware that Ryan loaded on your board into Arduino. You then make the change in configuration.h to change steps per mm in the X and Y axis. You then save the changes and upload to the Mega/Ramps using a USB cable. There are lots of tutorials on Youtube to cover the basics.

Hope this helps.