Jump to content

Using 3 wires to control parallel LCD display

Recommended Posts

Just a suggestion: If you want more than one button, but have only one port pin to spare, consider using a resistor ladder from Vcc to Vss (say sixteen 10K-ohm resistors), you could implement a 16 button keypad with one pin and the ADC on the 'G2231, assigning an instruction to a specific voltage.


Technically, you could have up to 1024 buttons, but who in their right mind would want so many?

Link to post
Share on other sites
  • 3 months later...
  • Replies 47
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Popular Posts

I have seen this done other ways, but I didn't want to deal with 7 pins, or 4 bits, etc., so I did it my way. You send 8 bits to shift register, then set data out to whatever RS should be, and finall

If anyone is interested, I found this display that uses 3 volts for both the display and backlight http://www.newhavendisplay.com/index.ph ... cts_id=282   onlinecomponents.com has them for $7.00 +

So Ive managed to get RobG's code to work on the Wintek 1 x 24 Character LCD Display Module that I got awhile ago from Electronic Goldmine for $1.99.   Here's the link: http://www.goldmine-elec

Posted Images

Hey Rob, I modified your sendDataArray(), thought this might help:

    void sendStr(char string[], char size) {
      int charIndex = 0;
      sendInstruction(0x80); // First line
        while(charIndex < size) {
    if(charIndex == (size / 2)) // half
      sendInstruction(0xC0); // Second line

This mod can print a 32-char string on a 16x2 display, while making sure all of the string is visible.

It can also be used for a 16x1 (logical 8x2), 20x2, and other small ones. It will, however, need slight changes for displays with more than two lines.


Hope this is useful!


BTW: this was written in C++

Link to post
Share on other sites
I lost track somwhere along the way of if the 4x3(4?) keybard and LCD still only used 3 pins on the 43

How about a catch up post with the lastest version and hardware hookup?

I will start new thread once I get all my LCD boards, should be less than 2 weeks.

Link to post
Share on other sites

I have a 20x4 line version of that display and while its possible to run the backlight from 3.3 the dropping resistor is pretty small.


For the above you need 15 milliamps for the backlight when its at 3 volts. If your running 3.3v for the micro your resistor would be ohms (3.3v -3.0v)/0.015 amps.


I personally don't feel comfit-able with that small of a dropping resistor, if your power supply should creep to 3.6 volts you would dump double the current into the display.


Anyone have luck running the 3v backlight displays off 3.3? I never actually tried it, I didn't feel safe doing it as I didn't get such a good deal on my display $21.95 for a NHD-0420DZ-FL-YBW-3.3, and it pulls a gosh awful 240ma for the back light. SHEESH.

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...