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10 years, 9 months ago.
I have Been working with lcd JHD204a interface with lpc1768 but not getting anything displayed?
I am using LPC 1768 development board for my project. I am interfacing 20x4 lcd display JHD 204a with it. I am using the code TextLCd_20x4_Test on this website for it. I have made all connections as per the datasheet but I am not getting any output. Please suggest solution
2 Answers
10 years, 9 months ago.
Are you sure the wiring is OK and the (contrast) voltages are correct. The example code that you used is rather old. Checkout my page on LCDs and try that library.
10 years, 9 months ago.
Thank you Wim for the answer but, which feature should i use for my lcd JHD204a out of spi, i2c and normal interface. Currently i am using the following code:
Hello World! for the TextLCD
- include "mbed.h"
- include "TextLCD.h"
TextLCD lcd(p15, p16, p17, p18, p19, p20, TextLCD::LCD20x4); rs, e, d4-d7 float mapxy[]={16.685212,74.471227,16.684432,74.471320,16.683956,74.471492,16.683797,74.471611,16.683612,74.471796}; int main() { lcd.printf("Lat:%f",mapxy[0]); lcd.locate(0,1); lcd.printf("Lon:%f",mapxy[1]); }
Please tell me wheather this code is compatible with the new library u suggested..? Thanx again for the suggestion..
Your code is using the normal 4-bit interface so the wiring for the data and controllines should be according to the pins you use in the declaration of lcd. The library will work with those settings. Make sure powersupply and contrast voltage is correct.
posted by 21 Feb 2014But I have checked all the connections and I have connected 1K pot between VEE pin and ground also I have provided proper voltage supply to the lcd...but still its not working also I have tried 16x2 lcd with the same program and its working but same code is not working with 20x4 lcd JHD204a
posted by 21 Feb 2014Some displays may have a pull-up resistor on VEE but in general the 1K pot should be connected to gnd and 5V on both ends and the wiper should be connected to VEE. You may also have to adjust the contrast voltage to see anything. Note that most LCDs need 5V powersupply and dont work properly on 3V3. The datalines are OK with 3V3. Make sure you have the R/W pin of the LCD at GND also. Some displays may have pull-down resistors but to make sure connect this pin to GND. Do you see anything on the display when power and contrast is connected. Usually you get a row of dark blocks even without programming the display.
posted by 21 Feb 2014OK, row of black blocks indicates that power and contrast are OK and that the display is functional. Next step is data- and controllines check and making sure the library works.
posted by 21 Feb 2014Wim I tried what you told about the VEE pin but the contrast is not changing...otherwise all things are working well..thank you so much ..
posted by 22 Feb 2014Is the voltage changing on the vee pin when you change the setting of the potmeter. What is the voltage. Most LCDs should be set at around 0.5 V for best results. The display goes dark or light for the largest part of the potmeter range and does not show much change in contrast anymore.
posted by 22 Feb 2014