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The Serial LCD/VFD controller are using a PIC16F628 to control the LCD module.
A MAX232 chip are used to convert the RS-232 signal to TTL level.
Not like the original MO LCD, I use a var-resistor to adjust the LCD's contrast, which is much simple. But cannot adjust the contrast level by serial command.
I guest Matrix-Orbital are using PIC's PWM feature which connect to a RC network to control the contrast voltage. Which is much
flexible, but I don't think which is much needed.
Following is the main component used:
The circuit are quite simple, you can click here to view the schematic chart in pdf format.
You can also click here to download the design file in Protel99 format.
The PCB design can fit most size of LCD/VFD. So, you can order some PCB and
build a backpack for any kind of LCD/VFD modules.
Here is my PCB Layout in PDF:
For your convenes, I also provide the PCB Layout in Protel99 SE format so
that you can easily modify it to match your needs.
Click here to download.
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There are several connectors on the PCB, they are for particular use. This session will describe the pin of these connectors.
JP1 - Power Connector
For internal mount, you should plug a stand 3.5' floppy driver power cable in
this socket to power the unit. Only the 5V output are used.
JP3 - External Power Connector
For external mount, you should plug a 3.5mm DC plug in this socket. The
outside of the plug should be ground.
JP2 - RS-232 connector
The connector for RS-232 interface.
| Pin Number | Feature |
| 1 | GND |
| 2 | TXD |
| 3 | RXD |
| 4 | NOT USED |
JP4 - GPO Connector
This connector are used to GPO output. Can be used to drive the LED.
| Pin Number | Feature |
| 1 | +5V |
| 2 | GPO 1 |
| 3 | +5V |
| 4 | GPO 2 |
JP6 - Alter LCD Backlight Connector
U5 - LCD/VFD Connector
Connector to connect to a 8x2 or 7x2 LCD/VFD Module.
U6 - LCD/VFD Connector
Connector to connect to a 16x1 LCD/VFD module.