Analyzing comm protocols without a scope

When you’re trying to debug something that works with a communications protocol like I2C or SPI, the usual approach is to break out an oscilloscope that is equipped with an analysis package for the protocol in question. Of course, scopes equipped with these protocol analysis packages tend to be among the higher-end models. A less expensive alternative is to use a protocol analyzer from Total Phase in Santa Clara, Calif. They provide the same sorts of debugging tools as scopes, such as triggering on a specific event or data word, but also have a much longer record length than most scopes for examining a long sequence of data communication events. Their price tag ranges from a few hundred dollars to about a grand. At the Tech Tour, Total Phase demoed the analyzers using the data coming off an ordinary orientation sensor.

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