Hey first I would like to thank you for providing this project. It is really a lot of fun and very educational. :)

Unfortunately, I haven't been able to get any further for several days and even the (detailed) documentation doesn't help at this point.

I am currently calibrating the inner motor (elbow) to get suitable values for servo_2_angle_pws. After inspecting the code I found out that you can add the argument servo=2 to the function bg.calibrate() to calibrate the second motor. But unfortunately the documentation does not provide further information. So far I got only bad values for servo_2_angle_pws, causing the pen to immediately run out of border or sending pulse widths outside the valid range. Therefore I have the following questions:

• How must the motor be placed on the protractor? (which direction) Is it correct in my uploaded picture (https://imgur.com/a/EA3IgWY)?
• At which value should I start? 90 or 0 degrees?
• in which range do I have to record the values? (-90 to 90 0 or 0 to 180, etc.?)
• which value do I have to give at the end of the calibration when I am asked how many degrees the offset angle is? 90 degrees?