Oscilloscopes, logic analyzers, and protocol analyzers are essential tools for analyzing and debugging signals, communication, and protocols in embedded systems. The choice of tool depends on the specific project requirements and the type of traffic that needs to be monitored.

Oscilloscopes and logic analyzers both measure signals but serve different purposes. Oscilloscopes capture and display analog signals as waveforms, making them ideal for analyzing signal integrity and timing. Logic analyzers, on the other hand, measure digital signals and represent them as binary values (0 or 1) based on voltage levels, providing a clear view of digital system behavior.

Protocol analyzers focus on analyzing traffic within specific communication protocols, such as USB, I2C, SPI, and CAN. They decode protocol-specific data, providing higher-levels insights for simplified debugging.

In this blog, we'll explore each of these tools in detail and discuss the best applications for using them.

What Does an Oscilloscope Do? Understanding Analog Signal Debugging

An oscilloscope is a device that is used to measure analog signals and typically offers 1-4 channels or signal inputs. It graphically represents voltage waveforms, showing how these signals change over time. The Y-axis displays voltage levels, while the X-axis represents time.

For embedded systems engineers, oscilloscopes are crucial for low-level electrical debugging, particularly when working with audio equipment, power supplies, and sensors. They help users assess key signal characteristics, such as voltage levels, frequency, distortions, noise, and timing relationships between signals. By capturing and displaying real-time snapshots of a signal’s waveform, oscilloscopes highlight inconsistencies in these areas that can compromise performance, such as spikes, irregularities, or timing mismatches. This allows engineers to quickly pinpoint issues like high-frequency noise or timing errors, which could lead to system instability, inaccurate sensor readings, or poor signal quality.

Oscilloscopes can be used in tandem with logic analyzers for more complex debugging of analog and digital signals.

Doug Baney, via Unsplash

What is a Logic Analyzer? Understanding Digital Signal Analysis

Similar to an oscilloscope, a logic analyzer is a device that is used to capture and display multiple signals. However, it focuses on a digital system’s or digital circuit’s logic signals, representing them in binary, as either a 0 or a 1. A 0 is shown when the measured input is “low” (below the voltage threshold), and a 1 is displayed when the input is “high” (above the voltage threshold).

Logic analyzers typically have anywhere between 8 and 136 channels, with each channel inputting one digital signal. Unlike oscilloscopes, logic analyzers do not display data in real time. Instead, they record data first, then display it, and measure the time between capture points. This allows users to navigate long recordings from a large amount of signal inputs, whereas an oscilloscope typically only measures up to 4 channels at a time.

Logic analyzers are ideal for digital circuit design and debugging, especially for identifying which signals are high and low. They are most commonly used for detecting incorrect signal transitions, timing mismatches, and logical errors in buses, microprocessors, and systems with complex digital signals.

Daichinger, CC BY-SA 4.0 via Wikimedia Commons

What is a Protocol Analyzer? Debugging Communication Protocols

A protocol analyzer is a tool used to capture and analyze signals and data traffic across specific communication channels, such as USB, I2C, SPI, and CAN. They provide crucial insight into the communication between embedded systems and their connected peripherals, helping to diagnose errors in data transfer. Protocol analyzers, such as those offered from Total Phase, capture and display data in real time, as opposed to others that display data post capture.

Total Phase Beagle I2C/SPI Protocol Analyzer

Unlike oscilloscopes and logic analyzers, protocol analyzers do not display the physical waveform of signals. Instead, they provide protocol data in hexadecimal (hex) format. This data is displayed as decoded, easy-to-understand packets, rather than raw bit streams.

By using protocol analyzers, engineers can easily capture transactions with pertinent data points, including:

• Transaction Timestamps
• Transaction Duration
• Error Messages
• Start or Stop Commands
• Device Addresses
• Decoded Data

By focusing on packet-level data, users can isolate and pinpoint specific transactions and errors that are not visible when using oscilloscopes or logic analyzers. This makes it easier to diagnose protocol-specific issues and conduct more thorough analysis and high-level debugging of embedded systems, networks, and FPGAs. For more information, check out this blog: The Advantages of Protocol Analyzers for Debugging Embedded Systems.

Total Phase Data Center Software I2C Capture

Comparing Oscilloscopes, Logic Analyzers, and Protocol Analyzers