My friend has got a 16x1 line lcd with a HD44780 controller properly wired up to his parallel port. Now here comes the problem, it wont accept anything from the vairous software, except for changing the contrast slightly. It displays 1/2 of the display areas with black boxes, and the other a blank. Any suggestions, would this be a fried lcd, or something really stupid that we have overlooked
I reckon that the bottom half of the screen will be filled with black boxes? If that is the case, the LCD has not been fully initialised. For two line LCD screens, you need to send a command to them to tell them to operate in two line mode; otherwise the bottom half of the screen will stay in it's 'off' state, which is black squares. Check out the EPE Magazine Article on these LCD screens, Part 1 here and Part 2 here for more info on the commands used. (Most of the commands etc are in part 1, you'll need adobe acrobat reader to view the files) I suspect that the behaviour is not due to a dead screen, but improperly set up software. Unfortunatley, I cannot help any further, since I've never wired one of these screens to the parallel port - I connect them to PIC microcontrollers. If you want to test the screen, you could try setting up the very simple circuit shown in part 1 of the article from EPE - it would allow you to send the contol commands to the screen using push buttons, which would prove whether the screem is working or not. My suggestions: Check whether pins 1 - 5 are connected correctly. Unless these 5 are connected correctly, the LCD will not work at all. Also check that the LCD control software is set up to use the right port. Also, check the 'mode' of the parallel port from the BIOS - the software may need it to be in a particular mode. (eg. CPP, bi-directional, etc) Hope some of this helps.
you think it could cause a problem if the parallel port mode is set to ECP ? and i blieve it has atleast 8 contact pins on the module.
