In the book Introduction to Microcontrollers, I alluded to the ability to expand your 2313 Experimenter System (2313ES.) On page 70, I showed a drawing of a breadboard attached to a 2313ES. This week, we will go ahead and expand our 2313ES with a medium-sized breadboard – this will provide pretty decent expansion capability, but will allow the 2313ES to keep it’s portability.
To start off, you will want to pick a piece of plastic, or something, to use as a base. In this example, we use a plastic base plate
from Tamiya (http://www.wrighthobbies.com/product.php?productid=62&cat=16&page=1 – Eddy was thinking about offering the base plates separately, write to him and ask him about this,) but you could use just about any flat-surfaced item. Consider a small piece of thin plywood, a small piece of metal, or plastic, cut from the side of something from the trash, a small clipboard without the metal clip, or maybe even the inside of the lid of a plastic pencil case (back-to-school specials abound right now.) The important thing here, is to just make sure that your kit and breadboard (and battery box, if you want it,) will fit.
Once you find your base, peel the backing off of the sticky foam tape on the bottom of your breadboard, and stick the breadboard into place on your base. Next you can solder two small pieces of jumper wire to the two power rail holes on your 2313ES printed circuit board (PCB.) Now, peel the backing off of the 2″X2″ foam tape that was included in your kit, and use it to mount your 2313ES near your breadboard. Then plug the the power wires into the power rails of your breadboard (you could also use the left-most holes in the power rail female headers, of your 2313ES, for a less permanent solution.) Finally, mount your battery box (if you want it) to your base; make sure that you leave access to both the sliding door and the power switch, as they are on opposite sides of the battery box. Also, if your breadboard has dual power rails on the top and bottom, you will need to connect the two +V, and the two Ground, rails, as we have on the right side of the photos.
Once you get your 2313ES and breadboard mounted, you will want to test the connections to make sure that everything is wired up properly. You can use a simple “blinkenlight” (http://www.instructables.com/id/Ghetto-Programming%3a-Getting-started-with-AVR-micro/#step6 – this is the same as the small test device that you built while testing your 2313ES,) to test power; place the negative lead (the one with the resistor) into the ground power rail, and the positive lead into the +V power rail. Place the power selection jumper over the Pgmr jumpers and connect the programmer and the LED should light up. You can also simulate the blinkenlight by just plugging an LED and resistor in to the breadboard.
If the LED does not light up, there is a bad connection between the 2313ES and your breadboard. Remember to disconnect power before changing any of the wiring, here. Recheck the wires connecting the two pieces. If you soldered the wires to the holes in the 2313ES, then disconnect one from the breadboard and temporarily replace it with a jumper plugged into the 2313ES’ female header for the power rail. Connect power again and check that the LED lights up. If it does, then the wire that you replaced is bad; recheck the soldering and maybe replace the wire. If the LED still does not work, then remove power, temporarily replace the other wire and check again. Again, do not forget to jumper the top and bottom V+ and Ground rails together. LESSON LEARNED – When I first connected this breadboard, I accidentally connect both V+ and Ground to the same rails – not good! Fortunately, this system is pretty durable. The USBASP (or the USB port on the computer) detected the short, and just shut down the power to prevent damage. As soon as I corrected that goof, everything worked again.
Once you get the LED to light, you may want to permanently mount the LED and resistor. Take a look at the photo for how you may want to do this. Once you get the parts placed and working, you will want to cut the leads short (make sure that you remember which LED lead is for the cathode (negative.) This will keep the LED and resistor neat and out of the way – in fact, you may want to use a tiny bit of glue, or epoxy (or hot glue) to keep them in place, it will be more durable that way.
This will provide a quick, and easy, pilot light, to let you know when your 2313ES has power applied. Just remember that the LED does draw power, even if you are not running any useful program on your Tiny2313 chip. This is not a lot of current, about 20mA, but it will help to drain your battery, if you are using the battery pack. Just make sure that you turn off the power switch on your battery box when you are not using the experimenter kit.
Next week, we will start adding stuff to the breadboard expansion. Stay tuned.