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Forum : Digole Serial Display : 12864 LCD/OLED module :

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128x64 GLCD (ST7920 V2 and Universal Serial Adapter

 Hi,

 

I bought three of these adapters and tried on two GLCDs and get just a blank screen.  Tried contrast with no help.

Using a scope, looks like data is going to the GLCD but can't adjust contrast to see it.

Using the UART demo on an Arduino Uno

am I missing something here?

RE:128x64 GLCD (ST7920 V2 and Universal Serial Adapter

Please provide your GLCD datasheet

RE:128x64 GLCD (ST7920 V2 and Universal Serial Adapter

 Don't have the datasheet.  It is this one:

 

https://www.ebay.com/itm/5V-12864-LCD-Display-Module-128x64-Dots-Graphic-Green-Color-Backlight-ST7920-US/272240808288?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649

Etched on back: 12864B V 2.0

RE:128x64 GLCD (ST7920 V2 and Universal Serial Adapter

  1. Please compare the pinout on the GLCD and our adapter, both must be same, otherwise, need to re-route the pinout
  2. Need to use the pot on the GLCD to adjust the contrast, not the pot on our adapter
  3. Also, don't forget to short the "P" jumper on the GLCD

RE:128x64 GLCD (ST7920 V2 and Universal Serial Adapter

 Pinout printed on GLCD matches your ST7920 chart.  Tried different setttings of the contrast on the GLCD.  I soldered female pins to the serial adapter and male to the GLCD

so cannot get at the GLCD's trimpot when the serial adapter is connected. I still only get a blank screen with a bright backlight.  This GLCD did test out ok using the

U8GLIB graphics test.

RE:128x64 GLCD (ST7920 V2 and Universal Serial Adapter

Connect Pin# 15 to VCC(That what "P" jumper does, Important: Don't short "P" and "S" jumpers at same time), if still not work, please show a picture of the back assemblered GLCD with our adapter

RE:128x64 GLCD (ST7920 V2 and Universal Serial Adapter

 pin 15 (PSB) to vcc no go.  I'll try to upload a pix

 

where do you do this?  This file uploader is disabled. Please check the "editor/filemanager/connectors/php/config.php" file

This is a windows 10 Machine.

Your web design is not the best.  How do I get the pix to you

 

RE:128x64 GLCD (ST7920 V2 and Universal Serial Adapter

Send to: question@digole.com

RE:128x64 GLCD (ST7920 V2 and Universal Serial Adapter

 Sent....G'night.

RE:128x64 GLCD (ST7920 V2 and Universal Serial Adapter

 After a lot of back and forth with Victor thru email, this is solved:  

1.  The GLCD needs to be in parallel mode

2,  There is a new auto buad library for Arduino

3.  After  downloading program to the Arduino, unplug the Arduino then plug it back in.  

This has got to the point that the Demo programs work.  Also if the contrast on the GLCD is too far

off, the trimpot on the adapter won't bring it in.

Thank you Victor for your help.

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