Open workbench logic sniffer
I bought me an Open Bench Logic Sniffer for Christmas. And I’ve finally found some time to try it out. I’ve bought to many toys to play with the last months 🙂 I bought it from Seeedstudio for 50$, but that didn’t include the probe cable. That cost another 6$, very cheap but I had a bit of bad luck. The cable arrived damaged, on 2 wires there is some missing insulation 🙁 I’ll have to order a couple of new ones with my next order from Seeedstudio.
Probe cable
The Open Bench Logic Sniffer is an open source logic analyzer. It’s designed to support the SUMP logic analyzer software at the lowest possible cost. The project is a collaboration between the Gadget Factory and Dangerous Prototypes.
I copied the above sentence from this page. There you’ll find all the information about the Open Bench Logic Sniffer.
I bought the logic analyzer as I’m using quite a lot of devices that use the serial, I2C or SPI bus. With a logic analyzer you can see what is happening on the bus and analyze the data.
I was a bit worried that I would not get the software to work but it turned out to be very straight forward. I use Gentoo/GNU Linux on my workstation. I already had the right kernel configuration, you need kernel support for “USB Modem”. I then downloaded the Logic Sniffer Client and fired it up.
To test the Open Bench Logic Analyzer I connected it to the I2C bus of my Bajduino Mega 3A. I had 2 I2C devices connected to the Bajduino, a DS3231 RTC and an I2C LCD.
Open bench logic sniffer
When I first tried capturing data I didn’t get much result. I then figured out that the default sampling rate is 200MHz. I use the Arduino Wire library to talk to the I2C devices which is only 100kHz. So I set it the sampling rate to 5MHz and got some better results.
Logic sniffer
I then selected tools -> I2C protocol analyzer and clicked analyze. The software automatically detected which channel is SDA and SCL and analyzed the data. These are the results I got:
I2C analysis results
I’ve also connected the Open Bench Logic Sniffer to the SPI bus of an ATMega328 and analyzed some data. Works pretty well, I did sometimes have to try and capture the data more then once to get a good result. But that could be due to the cheap probe cable.