Pulleys, encoder, transmission ratio

I have a hoverboard wheel (pole pairs 15) and AMT-102-V encoder. 54 teeth pulley on wheel and 18 teeth pulley on encoder axis. So the transmission ratio is 3:1. I’d like to start Odrive with autocalibrated motor and encoder for minimal movements on startup. How and where should I set the 3:1 ratio for this? Should I use “pole_pairs = 45” and leave “encoder_cpr = 8192” ?

In general you would set pole_pairs = 15, and encoder_cpr = 8192*3.

Please note that you may only use the index feature if your gear ratio can evenly divide your pole pairs. Specifically you must have:

pp \;\text{mod} \; R = 0

In your case you are okay with 3:1 because 3 divides 15 pole pairs.

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Thank you for the clarification. I changed my config accordingly
What worked for me is the other way around : pole_pairs = 15 / 3 and cpr = 8192.
Is there any further reading/document on that topic?