Features like interoperability and simple connectivity have led to the widespread use of USB protocol in embedded systems of almost all types. Despite the advantages, USB protocol in itself is quite complex. Quite naturally, detecting and isolating the source of a problem within the system might be a daunting task for an embedded systems engineer. Fortunately, a multitude of debugging tools are available that can offer valuable insight into the USB traffic.
Today we are going to look at some of the most common debugging tools such as Protocol Analyzers, Oscilloscopes and BERT Testers and how they differ from each other in usage and application.
Oscilloscopes – Oscilloscopes are pretty useful in debugging systems particularly for electrical issues, but the data is captured at a very low level. They are great for a quick diagnostic as the visual data generated by oscilloscopes can shed light on some of the most crucial parameters such as jitter, noise, and signal to noise ratio (SNR).In the early stages of development, system designers use oscilloscopes to look for an event of particular interest, decode the entire burst of serial data, etc. Besides, by using eye diagrams generated by oscilloscopes, the process of debugging can be made much less onerous. One can quickly find out if there are any signal integrity issues in their prototypes by using oscilloscopes but beyond that, they aren’t suitable for analyzing high-level data.
BERT Testers – BERT Testers are used to test the synchronous serial data over a channel in a system. Whenever data flows through a system, there is a possibility that some of the bits in the data might be corrupted at the destination. This is usually known as a bit error. Bit Errors can occur due to a variety of reasons such as noisy channels, ISI, impedance mismatches, etc.A bit error rate test is essential to determine the quality of link over the channel and figure out whether signal integrity is compromised. Hence, BERT Testers are used for this specific purpose.
A BERT tester works by sending a test stream of data through the channel and subsequently compares the data stream at the destination with a reference data stream. The result is usually reported as the number of error bits divided by the total number of bits that were present in the data stream. BERT testers also report the number of bits that were missed during the transmission.
To sum up, BERT testers reveal just a handful of information such as bit error rate and give a measure of the signal integrity and network performance.
Protocol Analyzers – Unlike Oscilloscopes and BERT testers, Protocol Analyzers allow designers and developers to debug their embedded systems at a higher level. Protocol analyzers come in two variants – Software and Hardware. Although the software variant offers an economic advantage, it is limited by the capabilities of the host computer’s hardware.The hardware variant has the ability to debug embedded hosts, and it also offers visibility into issues related to timing, transmission, and speed negotiation.
Protocol Analyzers have a big advantage over BERT testers and oscilloscopes as they allow the developers to view the data in the form of packets and not just individual bit streams. Moreover, protocol analyzers also offer a real-time display of the captured data to speed up the process of debugging a system.
While Oscilloscopes and BERT Testers are pretty useful in debugging embedded applications, it is evident that protocol analyzers have plenty of advantages over the other tools mentioned above.
If you have questions about our protocol analyzers or other Total Phase products, feel free to email us at sales@totalphase.com, or if you already own one of our devices and have a technical question, please submit a request for technical support.