Probing SPI signals with a logic analyzer
Even if you succeeded in receiving NMEA from your GPS module, you should attach a logic analyzer such as the Saleae Logic 8 if you have one. Probing the SPI signals helps us understand how the SPI protocol works and acts as a powerful debugging aid when things go wrong. In this section, we will use a Saleae Logic 8 to sample the SPI signals between the BeagleBone Black and ZOE-M8Q. If something is noticeably off with any of the four SPI signals, then a logic analyzer should make that mistake readily apparent.
The Saleae Logic 8 requires a laptop or desktop computer with a USB 2.0 port. The Saleae Logic 1 software is available for Linux, Mac OS X, and Windows. There is an installdriver.sh script that comes with the Linux version of Logic that grants the software permission to access the device. Find that script in the Logic installation's Drivers directory and run it from the command line so that you do not need to launch Logic with...
