Standard interfaces.

When testing any digital device you may need to analyze one or more data communication channel(s). In particular, you may want to see expolicitly how the timig of these signals relate to eachother.

At first glane, it appears to be a trivial task to take the timing charts from the necessary communication channel lines, determine the interface type and manually decode the recorded timing charts. But after making a few attempts to decode such timing charts, you may find it obvious that you do not want to perform this routine but tedious and laborious procedure very often.

PC USB oscilloscope can help by presenting some standard communications hardware interface protocols in the clearest possible format for your analysis.

To start decoding you must become familiar with specification of the analyzed interface and master its timing chart formats. This can take quite a lot of time, especially when you do not have a normal interface description handy. After familiarizing yourself with the interface you may find that decoding is actually interesting.

Generally, in most of interfaces there are some signs of bytes transmission start and end, except for SPI, when the data are transmitted without any delay. That's why decoding starts with the signs searching. Upon finding the start transmission sign, one starts decoding the data. This may raise questions about particularities of the analyzed protocol that require examination the specification of the analyzed interface, comparing the timing charts with their analogs in specification.

This can take a lot your time and divert you from other and probably more interesting tasks. We can state from experience about time expenditure required for interface timing charts decoding I2C (used in video capture board). When manually decoding for three and a half hours we managed to allot even 48 bytes, and even at that slow rate all the obtained information was thoroughly recorded on a paper subject to many potential errors. When decoding the same interface with analogous program (subsequent pilot model of logical analyzer) the whole communication cycle of 1026 bytes long was analyzed for 8 minutes but it took one and a half day to write the analysis program I2C.

This does not mean that without any preliminary preparation one can decode the data of any interface by pressing a couple of buttons for several minutes. In any case, it is necesary to read the selected interface specification before analyzing it, as no program can help you without unless you comprehend the interface operation principles.