LCD 12864 using MCP23017 [SOLVED]

Using Arduino Displays
1

Hello everybody.

I'm first time writing topic on forum so don't blame me please :slight_smile:

So i've got problem and I am really tired finding solution, please help...
I've got LCD 128x64 (don't know exactly on which chip) and Robodyn MCP23017 I2C adapter + Arduino Nano. Every seller attaching link to Nick's Gammon forum and on his huuge job with both of this chips (credits to him).
Trying his code and get a result as in attachment... Some wierd looking stripes, so i googled if somebody had had same problem and on a whole web i found only one image wich same as mine. Here on Arduino forum with nickname "shafiqurrehman" . But guys recommend him to not using MCP23017...

So finally my question is : Is it possible to modify code so it will work with MCP23017 via I2C ??? (because i soldered it very securely and have no clue how to disolder 20 pins safely)

Thank you in advance!

Links:

photo_fail.jpg
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2

To desolder safely: Cut through the header pins with Dremel or hacksaw. Then remove any remaining black plastic from the sawn pins. Desolder one pin at a time. Clean up tthe holes.

It "looks" like ST7920 display. Use the PSB pin to select SPI interface. Control the display with 3 pins.

The display will work at full speed with SPI.
You can probably bit-bang the ST7920 with your MCP23017 but it will be vary SLOW.

David.

3

david_prentice:
To desolder safely: Cut through the header pins with Dremel or hacksaw. Then remove any remaining black plastic from the sawn pins. Desolder one pin at a time. Clean up tthe holes.

It "looks" like ST7920 display. Use the PSB pin to select SPI interface. Control the display with 3 pins.

The display will work at full speed with SPI.
You can probably bit-bang the ST7920 with your MCP23017 but it will be vary SLOW.

David.

David thank you for so fast reply!

After 40 min struggling with desoldering i found that scheme you were talking about (see attachment). And yeah you were definitely right my LCD based on ST7920 and all you need a couple of wires, SPI and U8glib for Arduino IDE. And finally it works !!!

Thank you David, you made my day !)

Interfacing-circuit-diagram-of-Graphical-LCD-with-Arduino.png
Interfacing-circuit-diagram-of-Graphical-LCD-with-Arduino.png1200×1096 41.7 KB

4

You don't need the contrast pot. Most ST7920 boards sort out their own contrast. But they expect 5V on VCC.

Just disconnect VO. I suspect your display will work ok with n.c.

How did you do the desoldering?

It is unlikely that you can get sidecutters into the gap. But if you can, you might be able to butcher easier than with a hacksaw.

There is no way that you can disconnect a 20x1 header with a regular soldering iron.

David.