In SX Microcontrollers, SX/B Compiler and SX-Key Tool, ringlord wrote:

Ryan--

Here is another problem--that sorta sounds like yours--I solved by paying attention to the experts on this forum on many different threads. The scenario went like this . . .

I have a robot which I built. It's logic consisted of five Stamps, a master and four slaves all in a tightly coupled, pin-to-pin network. I used Parallax's HB-25 motor controllers to control my two gear motors.

This strange scenario was logic-hardware heavy and software lite. It worked perfectly. Soon, it was time for me to move on. So, I acquired one of [b]RobotWorkshop's[/b] drop-in SX48 modules, which are pin for pin compatible with the BS2p40. Not only did I get an interrupt structure, but the speed increase was stunning. As I was writing various pieces of test code, I soon discovered that I could not turn on the HB-25's. Well, the SX48 is much faster, so I figured the pulse widths sent to the HB-25s had to be different. This was correct and the one with which I was testing finally started doing something.

But, it was strangely erratic and I could not get the other one to work at all. I even tried different HB-25s. (I like'em!) No joy. Then, I remembered that long wires act like antennas. This may have dramatic affect on sensitive electronics. The electronics behind the pins of the microcontroller and the HB-25s are sensitive. I chose something that looked like the midpoint of the left HB-25's control wire and tied it to VSS (ground) via a 0.1uF ceramic capacitor. The HB-25 worked perfectly. Here is a very good, short [url=http://www.seattlerobotics.org/encoder/jun97/basics.html][b][u]essay[/u][/b][/url] on the subject.

I performed the same thing with the right HB-25 and received the same instant gratification. So, just for the heck of it, I stuck one in the very long line I use to control a big solid state relay. (I wasn't having any problems with it, but I was on a roll.) I also put one in my Bluetooth RX wire. I have read where folks sometimes use two capacitors, one near each end of the long wire.

Got any long wires from microcontroller pins to the Pololu controller?

--Bill

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