In this article we examine one of those products that are really simple yet can solve some really annoying problems. It is the "Go Between" Arduino shield from Mayhew Labs. What does the GBS do? You use it to solve a common problem that some prolific Arduino users can often face - how do I use two shields that require the same pins?
Using a clever matrix of solder pads, you can change the wiring between the analogue and digital pins. For example, here is the bare shield:
Now for an example problem. You two shields that need access to digital pins 3, 4 and 5 as also analogue pins 4 and 5. We call one shield the "top shield" which will sit above the GBS, and the second shield the "bottom" shield which will sit between the Arduino and the GBS. To solve the problem we will redirect the top shield's D3~5 to D6~8, and A4~5 to A0~1.
To redirect a pin (for example D3 to D6), we first locate the number along the "top digital pins" horizontal of the matrix (3). Then find the destination "bottom" pin row (6). Finally, bridge that pad on the matrix with solder. Our D3 to D6 conversion is shown with the green dot in the following:
Now for the rest, diverting D4 and D5 to D7 and D8 respectively, as well as analogue pins 4 and 5 to 0 and 1:
The next task is to connect the rest of the non-redirected pins. For example, D13 to D13. We do this by again bridging the matching pads:
Finally the sketch needs to be rewritten to understand that the top shield now uses D6~8 and A0~1. And we're done!
Try not to use too much solder, as you could accidentally bridge more pads than necessary. And you can always use some solder wick to remove the solder and reuse the shield again (and again...). Now the genius of the shield becomes more apparent.
The only downside to this shield is the PCB design - the days of square corners should be over now:
It is a small problem, but one nonetheless. Hopefully this is rectified in the next build run. Otherwise the "Go Between" Shield is a solution to a problem you may have one day, so perhaps keep one tucked away for "just in case".
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Posted by Posterous on January 17, 2012 in News.