Securepoint USB LCD using EA-DOG
During my practical training at Securepoint i've developed a frontpanel display which fits into the existing security-appliance hardware.
There is a usb header inside the equipment, so i decided to use it for my lcd project.
The firmware of the microcontroller is based on a modified version of Till Harbaum's LCD2USB. Because the space between case and mainboard requires a very small design, i've choosen EA-DOG series manufactured by Electronic Assembly.
Electronic Assembly offers different backlights and chip on glass displays, the user is able to combine them how he wants to. They offer panels from FSTN positive / negative to STN positive, negative, blue and also light reflective LCDs. Each module has 16 characters at one, two or three lines. 6 different backlights may be choosen!
I've used a thin 0,7mm circuit board and most of the components are placed as surface mounted devices. The prototype board needs some wires on, but if it is produced later there would be a double sided PCB.
The EA-DOG display is using a Sitronix ST7036 controller. It is nearly compatible to the HD44780 but needs some different initialization commands. It is also possible to drive the LCD from 3.3 volts. In that mode, the driving voltage for the liquid crystals is generated by the on board charge pump. This Voltage can be changed by a command to set the contrast. Setting contrast is also implemented in my version. Of course the backlight can also be switched or dimmed.
I'm using 3.3 Volts power supply for both, Atmel and LCD to meet the voltage requirements on the USB without using those ugly zener diodes on the data+ and data- pins. Because the Mega8 that was used by Till Harbaum is not specificated to run at 3.3 Volts, i've canged it to a Atmega48.
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