The 12864B module has an internal boost circuit that supports 3V to 5.5V. The default 4.5V voltage contrast display is the best. If the voltage is 5V or 3V and other voltages, please change the VR1 adjustable potentiometer on the back. The display effect is at least 3V and up to 5.5V. Since the module supports multiple voltages, and the current limiting resistor R12 R13 that controls the LED backlight is fixed at 68 ohms, the LED gets no voltage at 3V rating in the case of 3V-4V, and the LED backlight brightness does not have a normal 3.3V backlight. The current limiting resistor has a high brightness of 6.8 ohms, which is normal. 4V or more is not affected by resistance
Serial port selection, the default is serial port, and the parallel port is common. When the serial port is selected, it can be completed by selecting high and low levels. The second type can also be short-circuited to the serial port by the silk screen S on the back of the LCD screen, and the P point is short-circuited to the parallel port.
Since the third pin V0 has been disconnected by the JP2 jump point, if it needs to be adjusted by an external adjustable resistor, connect the JP2 jumper.
The LCD12864 is mainly composed of an LCD display (LCD PANEL), a controller, a driver, and a bias generating circuit.
The controller is mainly composed of an instruction register IR, a data register DR, a busy flag BF, an address counter AC, a display buffer DDRAM, a character generator CGROM, a user-defined character generator CGRAM, and a timing generation circuit.
The best working voltage of the module is: 3-5V;
Working temperature: 0 deg C ~ 50 deg C