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Al Williams

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Embedded Tools

May 30, 2014

I mentioned last time that programmers and electrical engineers have it rough because you can't really see what's going on in your design. That's probably why most of us love tools like oscilloscopes and logic analyzers.

Being a ham radio operator, I've had a scope since I was a kid. But buying a scope for personal use used to mean buying something old or something with very little capability, or both. Now you can get a scope that would have broke the bank a few years ago for about what a low-end PC would cost.

Still, even that's a bit much if you are just a casual user. There are a lot of inexpensive alternatives that connect to a PC or have a little screen but they aren't usually very good. They can still be better than nothing.

I did run into a sort of "in between" board the other day when I was writing about the LPC-Link debugger for the LPC-series ARM chips. I bought an LPC-Link 2 board for about $20 and then found that there was another product from Embedded Artists that included an LPC-Link 2 board. It was called LabTool.

It is a little hard to characterize exactly what it is. At the core, it is an ARM-based development board. The board contains an LPC4370, which is a 204 MHz Cortex M4 processor. There are also two extra Cortex M0 processors onboard and an 80MHz analog to digital converter. That's a lot of horsepower. The board mates with an LPC Link 2 board and you can detach the link board and use it for other things if you want.

Of course, that's only useful if you want to write some software. The selling point is the open source LabTool software that provides an 11-channel logic analyzer (up to 100 million samples per second), a 2-channel analog oscilloscope that can achieve up to 80 million samples per second, an 11-channel signal generator that can hit 80 million samples per second, and a 2-channel analog signal generate (up to 40 kHz). You can see an example run of the digital and analog sampling in the figure below.

The analog scope section has a nominal 6-MHz bandwidth (that can go up or down a little depending on your settings). So it isn't going to replace any of my big scopes, but it is a handy little device.

You probably could figure out that it doesn't do all those things at one time, either. The logic input and the analog input channels can work at the same time, but the signal generators prevent you from using the inputs. It is an either/or proposition.

To help make up for that, the default program load sets an example signal generating program in one of the Cortex M0 CPUs on the board. You can use this demo app to exercise the scope and logic analyzer functions.

The PC software is written using Qt, so it runs on different platforms. It also lets you have decoders (for example, in the figure above the top trace is a decoded UART and a bit below that is an I2C decoder). You can even use it with a Raspberry Pi, which opens up some interesting possibilities of making a portable device that displays on a mobile device. The software isn't bad, but I do wish it would just run under something like Sigrok.

The price is about $130. A bit on the high side for something that isn't a polished instrument. But then again, you can deduct the $20 you'd pay for the LPC Link 2 board you'd spend anyway.

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