Saleae Logic Analyzer – First Impressions

I bought myself a Saleae Logic 8 as I am constantly looking at oscilloscopes to help debugging problems with I/O on microcontrollers. It’s frustrating if you “see” nothing, beside you don’t get the results you want. Static signals are no problem: plug in an LED and you can see the state, but this does not work anymore as soon as frequencies larger than 10Hz are used. I2C runs at 100 or 400kHz…SPI even higher.

One fix would be a digital oscilloscope, but they are usually limited to 2 or 4 channels, with 4 channels being already expensive. Some can decode digital protocols too.

But there’s an alternative: Logic analyzers. And Saleae has a nice one; Logic 8: 8 channels, 100MHz digital and 10MHz analog sample rate, 8 channel. And for non-commercial use it’s 50% off!

Ordered one. 3 days later it arrived.

After few hours playing with it, it’s clear: I should have bought one much earlier. Seeing the I2C and SPI traffic or just pulses is so simple and so useful for debugging. Here an example:

1 is the I2C data channel, 2 is the clock. 3 is the same but recorded analog. 4 is the decoded I2C data and 5 is a decoder extension I wrote this afternoon for decoding the data for the PCF8583 I used here (in clock mode). This is easier and at the same time more useful than I thought.

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