Simple Logic Analyzers for Hobby Constructors

When you are working with digital circuits you have many devices that are connected with digital signals. While each signal when checked with a digital oscilloscope looks OK, the board may still not function as it should. In such case you need a digital logic analyser. Logic analysers are complex devices that sample many digital signals and show them on a single display. This way you can see them together with time relations. Logic analyser is an essential tool when you need to debug digital boards that refuse to work properly. Because of high sampling speeds and sophisticated software analysis, such devices are quite expensive. You will rarely find them on the bench of hobby constructor. Fortunately, there are cheaper alternatives. You can use either a simple PC oscilloscope or dedicated logic analyser for particular protocol: I2C, SPI or both. I2C logic analyser is a simple digital decoder. This device is built to sample and decode I2C signals. I2C bus may look OK but until you know what messages were sent and what integrated circuits on the bus responded you can not know where the problem is. I2C analyser takes care for this by decoding SCL and SDA signals. You can decode signals in real time or store them for future analysis. Some I2C analysers can also behave as I2C master and can generate I2C messages. This way you can test I2C devices on board without any microcontroller. This comes handy when there is no software written yet and you would like to test the board. SPI analyser is similar to I2C logic analyser - the only difference is the protocol the analyser decodes. SPI is a four-wire serial interface used for high-speed communications on board. While pro Logic Analysers are usually expensive, the price of digital PC oscilloscopes or I2C analysers is affordable also for average hobby constructor. Even larger digital boards can be analysed with simple devices. You only need knowledge and experience. Expensive devices can help but are not essential.

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