A logic analyzer for under $5

Recently I needed to get myself a logic analyzer. But for what I needed I didn’t want to spend much money on one. As I was surfing the web for an answer I was coming along a project called Sigrok. You can find out more about it here (sigrok.org). It’s basically a cross-platform signal analysis software. It’s all Open-Source and it supports many different hardware types. Read below how I came to my super cheap logic analyzer solution.

As I said the software supports various devices. You can find a list on the project page (sigrok.org/wiki/Supported_hardware). The thing I was really interested was a Cypress CY7C68013. Modules with this controller are pretty cheap. I got mine for less than 4 Euros on ebay.

Cypress CY7C68013A Board
Cypress CY7C68013A Board

Setting it up was pretty straight forward. See details on how to do this on the project page as well (sigrok.org/wiki/Lcsoft_Mini_Board). The chip runs on 3.3 V and if you want to probe 5V logic signals it is a good idea to add some basic protection. The website describes solutions like adding zener diodes and resistors and I thought I could use some 74HC245 in addition. I created a little board which fits right on top of the module. It looks like this:

Logic analyzer adapter board - 3D image
Logic analyzer adapter board – 3D image

Schematics and layout files are on Github. Feel free to use them. Here is an image of the final prototype module. Works really good.

Prototype of Logic Analyzer Adapter Board
Prototype of Logic Analyzer Adapter Board

I haven’t tested the speed of the module yet. But decoding an uart works pretty neat. You can record a signal trace and in a second step you can play around with different baud rate for decoding. Changing the baud rate after you recorded some data works pretty good. For example I had an issue with my ESP8266. By connecting the logic analyzer I was able to see that the ESP switched between different baud rates on startup. And I was able to decipher everything without recapturing it.

PulseView decoding UART
PulseView decoding UART

The conclusion: Really cheap and easy and definitely worth every cent.

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Published by

rsphysics

BY DAY: R&D engineer at a local company developing and testing electro-mechanical devices. BY NIGHT: Writing code, developing hardware, doing wonderful awesome stuff.

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