Channel mappings may differ on custom f3 boards, however the default F4 and clone boards like below should be the same.


Image result for sp racing f3

To connect this FC to a Flysky receiver in PWM mode the channel mapping is as follows:

 RX             FC

CH1   --->  CH2

CH2   --->  CH8

CH3   --->  CH1

CH4   --->  CH7

CH5   --->  CH4

CH6   --->  CH3