What is this Live Logic Tool – what is it good for?

Anyone who uses a logic analyzer knows where to find it – its on a cart in the back of the room. Its there for a reason – no one wants to use it. It takes too long to set up to get the data you are looking for. So you try to solve the problem with a scope until you get to the point where you have no choice. Then you drag out the logic analyzer.

What we realized is that engineers have to invest time in a test tool every time they want to make a measurement. With a scope you can get a little information by just touching the probe to the circuit – the signal is toggling, stuck high, or stuck low. Twisting the trigger level and time per div knobs gets you a stable display so you can see the shape of the waveform. Not much effort gets you a lot of data.

Live logic has the goal of giving you a lot of information with not much effort and to capture your hard to see digital signals. It uses scope probes so you can just touch your circuit. An activity LED on each channel immediately tells you if the signal is toggling. The graphic display is continuously updating and auto-scaling so you immediately see the waveform shape – less setup effort than a scope! In addition, the average voltage of your signal is shown on a DVM for each channel so you can check your logic supplies or PWM levels. You get a lot of information by just touching the probe to your signal.

OK, so why is this any better than my scope? Your scope is a great tool but it is designed to display analog signals. This fundamental requirement means that it must be sampling your signal continuously – a good thing if you are interested in measuring overshoot! But if you are looking at an RS-232 signal or an I2C transaction that happens only occasionally and is different every time, your scope will run out of memory, filling it with the static logic levels that exist between these transactions. Yes you can trigger on the first edge and see the start of the transaction but what about seeing the whole transaction or even better, the one that follows this one as well.

Live Logic was designed to only capture digital signals. It ignores those long periods of static logic levels between your transactions. It focuses on the action – it stores signal changes. The only thing that is stored are the transitions in your I2C signal – the thing you are trying to see. If your processor sleeps most of the time waking up to check the local temperature, its no problem. Live Logic can capture time spans as large as 73 minutes! Of course it does have a memory limit just like your scope but that memory is only used to store useful information.

That’s it. That’s the whole reason for Live Logic. It doesn’t replace your scope but its just as easy to use and it can capture digital signals that are challenging for your scope. Add an MB-500 with Live Logic to your bench and your life as an embedded engineer can become a whole lot easier.