| ??? 04/12/07 18:09 Read: times |
#137052 - You need more data! Responding to: ???'s previous message |
Jayanth Kumar said:
i have bought a jhd162a lcd. I have written an initializing program for the lcd. When i connect it only the backlight is glowing. Is there a way of testing if the lcd is working? When you connect it to what? I tried the procedure given in the forem
http://www.8052.com/forum/read.phtml?id=92858 i connected pin1(Vss) to gnd, pin2(Vcc) to +5v and and pin3(Vee) to gnd through a 1k resistor but nothing is glowing not even the backlight. when i connect pin15(led+) to +5v and pin16(led-) to gnd i get only the backlight glowing. That's how it should work. How can you test the LCD if you don't attach the reset of the signals to some intelligent source that can properly drive its signals? The datasheet is not complete it requires some chinese characters and nothing is present after a few pages. You should endeavor to obtain the proper datasheet. It wouldn't hurt to tell us on this forum what the manufacturer and part number for your LCD are. Some people might be able to help. They can't do that with no part/model number. please, I need some help in checking if my lcd is working.
thank you jayanth I'd say that you probably need to verify that it works at all, and then verify that you have a properly working interface. You need to obtain the proper datasheet. That's a given. Secondly, given the current circumstance, you probably have an HD44780 or equivalent. That's the controller IC. You can get lots of information about how to "talk" to it. Be sure that you use all the available interface signals so you can read the busy status bit. If you don't know what the proper bias voltage (pin 3) is supposed to be, you need to have a potentiometer between +5 and -5 volts and feed the 1K series resistor to pin 3 from the wiper. That way you can sweep the bias voltage in order to see where you eventually have sufficient bias to provide enough contrast to make the character blocks visible. When they become visible, you've gone too far, so back off a bit in whichever direction makes that happen. Without extensive driver code, you can't fully test the device. You should never, Never, NEVER buy a surplus LCD until you know it functions properly or are given an enforcible warranty that it does. If you want to build a tester using an 805x, you can do that using code that's published here on this site. Be sure to use one of the code samples that actually reads the busy flag, not one that uses open-loop timing, since you don't know what the parameters for your LCD are. RE |
