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Troubleshoot, fix problems on the go

Posted: 09 Apr 2014  Print Version  Bookmark and Share

Keywords:troubleshooting  oscilloscopes  PicoScope  FPGA  Arbitrary Waveform Generator 

These days, engineers and technicians face increasingly complex and critical troubleshooting tasks. Designs that work fine in the lab can sometimes fail in the field, causing customer dissatisfaction, lost production, expensive repair bills and, sometimes, safety concerns. With the customer impatient to get their system fixed as rapidly as possible there is huge pressure to troubleshoot and fix problems quickly and accurately.

Engineers need lightweight, and compact, but powerful tools to take with them on-site to validate device functionality, identify failures, and trace the root cause by capturing waveform errors such as timing faults, crosstalk, transients, power quality issues and more.

USB oscilloscopes are small enough to fit in a jacket pocket or a laptop bag, so can be taken anywhere. But they have functionality and performance that match, or exceed, many laboratory instruments, enabling engineers and technicians to tackle these challenges—quickly and easily.

This article will review some common field-failure examples and show how the PicoScope 2200A and 5000 Series oscilloscopes can be used to capture and isolate waveform anomalies to identify source of the problems.

Design verification in the lab
Product design is no easy task, but engineers in the lab do typically have access to all the basic tools they need to get the job done: design automation and simulation tools, plus an array of hardware verification tools including an oscilloscope, signal generator, logic analyser, DVM, precision power supply and the rest. On top of that there is generally a design team if the FPGA engineer is struggling with a memory interface problem he or she can tap the shoulder of the hardware design manager and they can consult other team members to examine and resolve the issue together.

In the field
If design problems show up once the product is deployed, the dynamics are quite different. First, the customer is likely not best pleased and will expect prompt action to resolve the issue. If the product is being used in a manufacturing process the economic consequences of field failure can be very significant, so time really is of the essence. Worse still, if the product is being used in a safety-critical or medical application, people's lives can be put at risk. The pressure to find the root cause of a design problem and rectify it is enormous.

Pity, then, the unlucky design engineer who is plucked from the warmth of the design lab and sent long distance to find and solve an obscure design flaw that didnt show up during the development process. She or he will be working in an unfamiliar environment, overseen by the dissatisfied, and potentially hostile, customer with no immediate team on hand to help. Furthermore, transporting the much-needed lab equipment on-site is impractical due to shipping constraints and the in-house design team are using it for the next project in any case!

Whats needed is a small, lightweight, hardware verification tool with functionality that matches or surpasses the verification tools that were available in the laboratory. Further, it needs to enable sharing of results and data so that other members of the design team, back in the lab, can see what is going on in the field, do their own analysis, and behave as an integrated team to find the cause of the problem and resolve it.

PicoScope
PicoScope USB oscilloscopes are small, light, alternatives to traditional benchtop instruments. A PicoScope fits in a laptop bag, yet offers 2 or 4 channels, up to 500MHz bandwidth, a built-in signal source and 16 digital channels on MSO models. High-end features such as advanced triggering, serial bus decoding, mask limit testing and waveform mathematics are included as standard. Buffer memory up to 2 gigasamples enables in-depth analysis of complex systems that can be performed in real time by the PicoScope user, or off-line and remotely by other engineers using their own licence-free copy of the PicoScope software.

In this article well look at examples of the PicoScope 2200A two-channel pocket oscilloscope and the PicoScope 5000 four-channel flexible resolution model.

Basic signal integrity measurements
The first task for an engineer who needs to find a design flaw is to perform basic signal integrity and timing checks. Does the clock distribution look okay? Are the logic edge rates in spec? Is there evidence of noise or crosstalk that could be interfering with the circuit behaviour? Is the design stable over time and with changes of external parameters such as temperature, supply voltage and in the presence of EMI?

Figure 1: Screenshot from a PicoScope 2200A showing capture of a simple I2C clock and data waveform. The display has been split into four view panels which enable the user to view different portions of a captured signal by zooming in on the waveform features of interest.


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