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Wednesday, November 9, 2011

Letting your microcontroller communicate with the world outside

By Ian Harris


So, you've got a microcontroller based project and you're searching for a method for it to communicate to the outside world. What are the options?

You might use several LEDs, perhaps of different colours, to indicate different states. This is excellent for showing simple states, like the bootloader is running, or the correct program you expected loaded on the device. That's fine, but you can't show all that much - flashing LEDs will only leave you guessing, if you try to indicate too much.

An LCD display is a great way of displaying much more, you can show text, numbers, results, even a menuing system. Most LCD displays will enable you to send custom characters as well , even tho only a few, so simple graphics are practical. However, most LCD displays are quite tiny, and are only really viewable when you're very close to the display itself.

An alternative technique is an alphanumeric LED display. This is just like the numeric display in your clock-radio, except instead of having seven segments, it has14, or in a number of cases sixteen. A 14 segment display allows a much larger selection of characters than a seven segment display. Letters as well as numbers can be displayed and even varied punctuation symbols. And the big advantage is that these displays are at least half an inch tall - and some are even an inch high or more! This suggests they can be viewed from across the room, making it easy to understand what your project is making an attempt to say.

Talking with alphanumeric LED displays varies according to the particular module you have. Sometimes it is a matter of shifting in bits one at a time, since each digit has a shift register linked with it. In some other cases, the display module has a microcontroller inserted in the display itself, so that you can communicate using asynchronous serial commands. In both cases, just a couple of pins from your microcontroller are required to display bright, colored text.

An additional benefit of these displays is the facility to chain one to the next one. So a 4 digit sixteen segment display can be attached to the following one - thereby creating a much larger display. This strategy of daisy chaining means you are not limited by the number of digits of the display itself, only by how many you wish to link together.

For an enjoyable, colorful way of displaying information, try an alphanumeric LED display to add additional character to your project.




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