When developing and debugging I2C based hardware and software, it is extremely helpful to see exactly what is happening on the I2C bus. This article describes one example where the BusPro-I hardware and I2C Exerciser software were used to debug an I2C interface. The article presents a specific example of generating a boundary-scan script test in ScanExpress TPG to drive the I2C bus signals via JTAG. Although this article describes a specific problem that occurred in a single hardware development environment, the same general techniques described will also apply to other applications as well.