How to control IO pin signal strength on AT&T SK

roberthartman's picture

We're using SPI on the AT&T IoT Starter Kit (2nd Gen) to communicate with another board. We're having an issue with our wring setup, and HW guys are wondering if there is a way to control this for the SPI lines. I could not see anything in the Linux spidev nor the hwlib drivers that would allow me to do so. Is this something that would require a kernel rebuild?

jflynn129's picture

Hi Robert, to my knowledge, there is no way to control the SPI HW lines individually.  The SPI interface is controlled by the Qualcomm MDM9607 as an integrated module (that is how WNC implemented).  The easiest way to observe the SPI interface I have found is to put a logic analyzer on the SPI interface and do a loopback on it.  This will show the Clock, Input, Output and chip select lines as data is written to the SPI interface.  This is done in the factory test SW (see MAX312855.cpp, loopbackTest) where the input/output is looped back on itself.