USB On-The-Go (OTG) is a specification that allows portable USB devices to be cabled together without a computer. When using the standard USB protocol, one device, most commonly a computer, will always be the host, and the other device will always be the peripheral. With a USB OTG cable, both devices can act as either a host or peripheral, allowing for interaction between two traditionally peripheral devices. Three new communication protocols have been introduced to the USB 2.0 specification with the advent of USB OTG: Attach Detection Protocol (ADP), Session Request Protocol (SRP), and Host Negotiation Protocol (HNP). Role Swap Protocol (RSP) has been introduced to the USB 3.0 specification.

We are using the Aardvark I2C/SPI Host Adapter to program SPI devices. We successfully completed the first two stages of verifying the software. However, we are having issues with the third stage – automating the process. There was no activity, which was verified on an oscilloscope.