Saleae ‘Logic’ Logic Analyser
A while back I had the need of a logic analyser, and as my philosophy buy rather than borrow or hire, I looked around the web. During my travels, I came across a small unit made by a company called Saleae.
This unit as it turned out, was exactly what I was looking for, it handles 8 channels, it is small, and there is a Mac version of the software. What else could a person ask for? Well it turns out that they now also make a 16 channel version, which I don’t need.
So how well does the software work I hear you ask. Well using the Mac version, is a joy. First download the software from their website, while you wait for delivery of your new toy. The software will run in demo mode if you don’t have the hardware connected. Testing in the demo mode gives you a great feel for how well the product works. You can manipulate everything just as if you had captured live data.
Once the hardware is in your hands, plug it in. It matters not whether the software is running or not, as the software will link with the hardware, the moment they are both present – it just works.
Setting up is a snap, plug the capture lead into the hardware, connect the ground, then the needed channels. Then on the screen, select the number of samples you wish to capture, set the rate you wish to capture the data at – remember to capture at least 2 samples from your shortest expected high or low. Label your channels (it helps to remember what you are looking at), set the trigger on your selected channel, click the capture button and bingo you will have a screen that looks similar to the screen below.I have updated the screen shot to the latest software as of 4 Oct 14. Unfortunately WordPress seems to really compress the images and they look blurry. Maybe someone can tell me how to fix this. Anyway, I have included a couple of close ups to provide a better look.
If one or more of your channels is serial data such as asynchronous, SPI, I2C, then you can invoke an analyser on that channel and the software will interpret the data & display it in Ascii, Hex or binary. (Did the processor really send “Hello World” to the screen?). It is a doddle to check.
Having captured some data, on the right side of the screen is a readout of the times between transitions the cursor is currently over (In the diagram above, the arrows showing on Channel 7 indicate the time of the low – left arrow and the time of the low and high indicated by the right arrow. You may want to see how long after the local transmitter sent a packet to the remote end did the remote end take to reply? Was the reply what you expected? This is all easily measured with this device.
I was recently setting up an XBee link, and used the Logic analyser to help work my way through the communication issues I was encountering. I probably could have solved the problem without the Logic probe, but instead of spending several hours writing a monitor module, I spent several minutes getting out the probe, connecting it, and I could immediately see I had an addressing problem, which I would have been hard pressed to capture otherwise.
The hardware comes in a nice protective case, and includes The Logic Hardware, USB cable, Sampling cable and 9 clips for attaching to the circuit under test. As a bonus, if you are working with an Arduino board, the sampling cable plugs straight on to the inter board header pins which provides a reliable and simple connection method.
All in all it is a great addition to my collection of test gear, and I thoroughly recommend Saleae for their product, service and product quality.