Author Topic: NHD-0420H1Z-FL-GBW-33V3 pull-ups and pull-downs in 4 bit mode  (Read 3016 times)

richardwright

  • Newbie
  • *
  • Posts: 3
  • Karma: 0
    • View Profile
NHD-0420H1Z-FL-GBW-33V3 pull-ups and pull-downs in 4 bit mode
« on: December 10, 2014, 09:53:35 AM »
Can anyone confirm the NHD-0420H1Z-FL-GBW-33V3 does or does not require pull-ups on E,RS,andR/W?  Additionally, in 4-bit mode are there internal pull-downs on the low nibble lines.  Is the external circuit expected to provide either pull-ups or pull-downs in 4-bit mode on any lines?

Michael_L

  • Administrator
  • Hero Member
  • *****
  • Posts: 356
  • Karma: 33
    • View Profile
Re: NHD-0420H1Z-FL-GBW-33V3 pull-ups and pull-downs in 4 bit mode
« Reply #1 on: December 10, 2014, 11:22:12 AM »
No pull-ups/pull-downs are required on any of the signals on this display (even in 4-bit mode).  You may view in the datasheet that the wiring diagram for the display shows only one resistor, and it is adjustable (potentiometer) to allow for contrast adjustment.

richardwright

  • Newbie
  • *
  • Posts: 3
  • Karma: 0
    • View Profile
Re: NHD-0420H1Z-FL-GBW-33V3 pull-ups and pull-downs in 4 bit mode
« Reply #2 on: December 10, 2014, 12:09:49 PM »
Great, thank you.  I did see the diagram in the data sheet, in addition to the internal wiring diagram in the ST7066U manual showing pull-ups on RS and R/W but not E - both great references.  It seemed clear but I wanted to get a confirmation just in case.

We are stuck on the use of the NHD-0420H1Z-FL-GBW-33V3.  The display does illuminate when powered and initialized but no cursor or characters are ever visible.  It also seems as if the DDRAM addresses are not incrementing when data is written to them or event when an explicit address command is sent to the controller.  Oddly, the BF does seem to be working...

I was hoping there was a requirement for external components and that perhaps floating lines were responsible - on the off chance they would stop the controller from initializing properly if they were absent.


Given that is not the case - can you suggest a means to troubleshoot the internal state of the controller?  How can we verify it is in fact initialized?  Is there, for example, a DDRAM location I can attempt to read that holds the current Function Set data?  I could write various values via Function Set and read them back to verify their application.

Another thought is that perhaps the voltages to VDD, V0, and LED+ are misconfigured - high V0 for example (V0 = VDD).  But if that were the case I would expect the call to set the AC or calls to write characters would result in those address values coming back with the BF.
« Last Edit: December 10, 2014, 12:11:27 PM by richardwright »

Michael_L

  • Administrator
  • Hero Member
  • *****
  • Posts: 356
  • Karma: 33
    • View Profile
Re: NHD-0420H1Z-FL-GBW-33V3 pull-ups and pull-downs in 4 bit mode
« Reply #3 on: December 15, 2014, 05:12:27 PM »
The BF would be the only way I know of to check the internal state of the controller.  What voltage are you applying to V0?  The reason I ask is because it may be possible you have characters on the screen but cannot see them due to improper contrast voltage.  Do you have any character LCD library functions you are using, or is your code from scratch?  Have you successfully used this setup to communicate to an LCD previously?

 

NHD‐3.5‐320240MF‐ATXL#‐CTP‐1 Problem with standby mode

Started by guenterBoard TFTs

Replies: 0
Views: 1949
Last post June 16, 2016, 12:14:36 PM
by guenter
NHD0420CW-A*3 tHREE LINE MODE, MIDDLE LINE DOUBLE HEIGHT

Started by wb2dybBoard OLEDs

Replies: 3
Views: 3119
Last post July 01, 2015, 09:49:46 AM
by Paul_B
Problems with a NHD‐0420H1Z‐FL‐GBW‐3V3

Started by c2hollowBoard Character LCDs

Replies: 8
Views: 4354
Last post October 27, 2017, 11:51:46 AM
by NoellEagan
NHD-2.4-240320CF-CSXN#-F works in 18 bits(262K colors) mode

Started by charlieBoard TFTs

Replies: 3
Views: 2173
Last post March 15, 2016, 10:39:50 AM
by Saurabh_B
Text orientation not changing with Extended Entry Mode Set Register

Started by tekknojoeBoard OLEDs

Replies: 5
Views: 1409
Last post January 27, 2017, 10:13:57 AM
by jmadsenee