Article about the SPI interface on Wikipedia.
According to this article, the SPI interface can be run in one of two modes:
- Single master - single slave.
(No chip-select. The slave’s chip-select is tied to its logical active state if c/s exists.)
- Single master - multiple slaves. (Using individual chip-select lines for each slave device.)
Based on what I remember of both the Raspberry Pi GPIO pin out and the GPG board schematic, you are using the single master - single slave mode of communication, right?
I am also assuming that the SPI buss is the logical connection between the Pi itself and the GoPiGo controller board.
(i.e. Communication between the two devices occurs over SPI, and the other signals (like I2c) are passed through for the user to do with as he sees fit.)
Is this correct?
If so, it explains why the Vellemann 3.5" touchscreen caused Charlie to loose his mind - it uses the SPI buss too.