The present work covers a software based test of the SPI peripheral included in the Pulpissimo SOC and, in particular, of its internal controller. Functional test of peripheral controllers can be a very difficult task, since they are very deeply embedded in the peripheral and therefore very difficult to access and their responses are hard to observe. In the case of the Pulpissimo the task was not straightforward, as the built-in functions present in the C library didn’t test the SPI controller, and therefore an ad hoc driver had to be written, in order to send arbitrary commands and get the finite state machine of the SPI controller to reach all possible states, thus achieving an adequate coverage.