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Buyers Guide

Saleae Logic Analyzer

By Mark Casilang

Take the pain out of debugging with the Saleae Logic Analyzer

Saleae Logic: A Step Above

Logic Pro Red Logic analyzers allow designers to optimize and debug the hardware in their digital prototyping systems and allow technicians to identify and fix problems within malfunctioning systems. They capture and display multiple signals from a digital system or circuit and correlate assembly with source-level software or change recorded data into state machine traces, timing diagrams, assembly language, or protocol decodes.

Created with the user in mind, Saleae Logic Analyzers are ultra-portable for easy storage and carry and have an impressive look and feel. The smallest model is a mere 1.66" x 1.66" x 0.39" and the largest model is still only 3.6" x 3.6" x 0.59". The Logic software works on any Windows, Mac, or Linux operating system, allowing the user to easily work cross-platform. Unlike a typical oscilloscope or other logic analyzers, Saleae Logic can record continuously.

The history of logic analyzers

Logic analyzers are primarily used for testing complex digital circuits that make up computers. They were developed to undertake fault-finding and debugging on microprocessor based systems. They work equivalently to the way an oscilloscope displays and aids in the analysis of analog signals but use both digital and analog signals instead. They do not completely replace oscilloscopes, but for some applications, they can provide a much better result.

There are three types of logic analyzers: modular, portable and PC-based.

Modular

Modular logic analyzers are the standard form seen in labs. They have a chassis and multiple modules. They are the most expensive and provide the highest level of functionality.

Portable

Portable logic analyzers are more compact than modular log analyzers. They have everything integrated into a single module with a screen.

PC-based

PC-based logic analyzers are smaller and connect to a computer through USB or Ethernet cable. They don't require an additional monitor since they display through the PC's existing keyboard, display and CPU. PC-based logic analyzers are the least expensive, but are limited in terms of power compared to modular or portable analyzers. The Saleae Logic is a PC-based logic analyzer.

Saleae features vs. other logic analyzers


PC-based Logic Analyzer from Saleae
PC-based Logic Analyzer from Saleae


The Saleae Logic Analyzer has applications not included with other logic analyzers. Its top application allows it to decode multiple protocols at once while also displaying the original waveform. The user is able to compare data more easily than dedicated protocol decoding tools, saving both time and money.

Saleae features vs. other logic analyzers


It also has an application for debugging microcontroller peripherals. Pinpointing where an error is occurring helps the user troubleshoot in no time. This is especially useful when several different parts are responding to each other at once.

It can also be used as a USB-based data logger. The User Interface (UI) easily records and deciphers data saving its user frustration. You can download the software for free and use in simulation mode without the hardware from Saleae.com. Saleae also provides a software development kit (SDK) and an application programing interface (API).

In addition, Saleae offers a three year, no questions asked warranty that covers any malfunction despite its cause.

Saleae models and specs

Models for the Logic: Logic 4, Logic 8, Logic Pro 8 and Logic Pro 16. The number indicates the amount of inputs. The Logic 4 is the only model that has 3 digital inputs and one input that's both digital and analog. In all other models, all inputs are both digital and analog. Each input has a dedicated ground wire to provide optimal signal integrity with a flying lead test probe.

Logic 8 and up models feature the Xilinx Spartan 6 FPGA, which interface to the USB bridge, digital inputs and the analog-to-digital converter (ADC). The FPGA is capable of performing over 5 billion DSP operations per second. There is a low jitter of the ADC sampling clock to assure the signal-to-noise ratio (SNR) is not degraded.

The digital and analog sample rates vary between models. The Logic 4 digital sample rate and signal has 12 MS/s and 3 MHz, 6 MS/s and 600 kHz for analog. The Logic 8 specs are 100 MS/s and 25 MHz for digital and 10 MS/s and 1 MHz for analog. All Pro models feature 500 MS/s and 100 MHz for digital, and analog of 50 MS/s and 5 MHz.

Since Saleae is a PC-based logic analyzer, simply plug in the wire harness to your PC and it works with your computer's set up. You will need to download the software from Saleae.com. After the software is installed, setup the number and type of input channels, recording length and specific bandwidth. You can also customize the color and brightness of the LED.

Saleae features vs. other logic analyzers
Inside the Logic – Analog Side

Saleae features vs. other logic analyzers
Inside the Logic – Digital Side

After setting up your application, connect the digital circuit. Simply click "Start Simulation" to begin collecting data. The navigation is also easy–drag left or right and use the mouse to control zoom. Hover over data to view measurements and right click to display additional measurements.

The Saleae Logic Analyzer also allows the user to add triggers of digital edges or analog pulses in order to search for those events. You can include annotations of bookmarks, notes, timing markers and measurements to record specific events or decipher data.

Saleae Logic Software UI
Saleae Logic Software UI


The Saleae Logic Analyzer is one of the best logic analyzers available. Affordable for the hobbyist, its compact size and user friendly UI delivers efficient results with functionality comparable to a portable logic analyzer. Once you start using the Logic, you may never want to go back to other bulky, complicated logic analyzers.


Editor's Note: Are you an expert at using modular logic analyzers? Try out the Logic and let us know how they compare by emailing [email protected]

Mark is a graduate from Cal Poly, San Luis Obispo in Electrical Engineering. He is originally from sunny San Diego, CA. His interests include travelling, movies, games, sports, music, playing tennis and going to the beach.
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