There are quite a few possible ways to approach this. The Pixy site has info about some of the ways: http://cmucam.org/projects/cmucam5/wiki/Hooking_up_Pixy_to_a_Microcontroller_like_an_Arduino
The Peggy 2 is an Arduino-compatible board, and you can hook the two of them up in different ways. The default method– using the 6-pin SPI port — is not actually suitable because the Peggy 2 uses SPI output to control the LED matrix. However, you can use either the I2C or (best of all) the UART option. Use the “SER” jumper option when building the Peggy 2, and the Peggy2serial library for controlling it.
