LCD beginner

[RoveyDoveyGrovey]

i bought a lcd with a built in controller i think the model is winstar wh1602b in case that means anything to anybody. i thought i'd start with the basics and hook the lcd up in the way described in the pdf file found in the lcd sticky thread under fundementals.

Anyway i tried entering the code 00001111 whic is supposed to display a flashing cursor, but needless to say im getting nothing. im confident i have set up the circuit as shown, but there are a couple of differences, my lcd has an extra 2 pins K and A, i connected A to 5v and K to 0v and instead of using switchs im using wires that i just plug in and pull out of the breadboard, not ideal i know.

Im also getting a curious thing whereby i connect a negative voltage to the contrast pin and some squares appear but then slowly degrade and disappear, if i increase the voltage they just degrade a bit more slowly.

anyway if you made to the end without falling a sleep, then thank you, i would appreciate a push in the right direction.

 

[Sceadwian]

The LCD has to be initialized before you can send it commands it will not respond until initialization.

The extra A and K are for an LED backlight, this has to be turned on in software even if voltage is applied, be careful as it probably requires a current limiting resistor.

The contrast line should be fed from the center of a 10K pot connected between ground and VCC, and according to what I've read bypassed to ground with a 100nf cap. The LCD unit itself should also be bypassed (capacitor directly between it's VCC and GND pins) with a 10uF cap.

 

[RoveyDoveyGrovey]

cheers i'll give some of that a go. i did initially try using a pot with one end connected to pin 3 the middle one to the negative supply and the final one to ground, but this would only create the degrading blocks, i got better results just connecting pin 3 to the -ve supply. at least one thing is working then, the back light works fine when k and a 4e connected.

How do you initialise it?

 

[Sceadwian]

Attached is the datasheet for the actual controller that runs your LCD module. Keep in mind from what I've run across looking this up this unit is NOT compatible (at least init) with Hitachi LCD modules, most of the information you find out there will be for Hitachi modules. Please note the wait requirements for initialization, they're critical.

The required init procedure for 8bit data mode is listed on page 26, the next page has the 4 bit datamode init procedure.

Warning, early on in this document it states that the controller will automatically initialize during power up, this however is ONLY THE CONTROLLER, this is not the same as the required user initialization that must be done before the controller will take in the proper data for display control and actually output something. It's basically the safe zone for the controller and defaults to off for everything. The init procedure listed turns the display on and allows command to do something.

I would strongly recommend using the recommended 10k POT and bypass cap to drive the contrast line, set to middle until you have the device initialized and you attempt to display something. If you get no results from that try sweeting the POT position from rail to rail to see what it changes.