We learn to use the protocol HD44780

We use the protocol "HD44780"

Hi, on this occasion I would like to describe the operation and the commands needed to properly drive a liquid crystal display. Now they are many in the shops and stalls at truly attractive ranging from about five Euros and beyond for more sophisticated types. To be precise, we will analyze all the control codes to activate a display with two lines of sixteen characters each, working with logic "HD44780" Hitachi. Right now I want to clarify that when we speak of sixteen characters per line, we refer to the characters that you see, because in reality there are twenty-four other off-screen for a total of forty characters per line.

To better explain the ideas I will also use a simple program that I made ​​in "visual basic", with which we can through the parallel port of a personal computer, send control codes to the various display and check the effects immediately. The electrical circuit used by me and that I propose, shows only the connections between the parallel port of a PC and display, in fact, the evidence shows that we will do it, no extra components. For reasons of security and protection circuits concerned is advisable to use a battery with a voltage total of 4 to 5 volts. In my case I used three AA batteries, for a total of about 4.5 volts.

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