Segment LCD screens have the characteristics of ordinary digital tubes, but also the characteristics of dot matrix LCDs, fixed graphics, cost-saving and beautiful.
The segment LCD screen interface is generally a parallel port and can be driven by a single-chip microcomputer. Don’t think that using a single-chip microcomputer to drive the broken code screen is DC driven. In fact, the segment code screen is AC driven. What is AC? Rectangular wave, sine wave, etc. . You may often use driver chips, such as HT1621, etc., but some segment screens have fewer IO ports, or if there are enough Io ports, you don’t need to write the driver of the controller. However, there is a prerequisite for IO analog driving segment liquid crystal, that is, IO must be tri-state, for the following reasons:
The first step is the important parameters of the segment LCD screen: working voltage, duty cycle, and bias ratio. These three parameters are very important and must be met.
The second step, the driving method: According to the driving principle of LCD, it can be known that only AC voltage can be applied to the LCD pixel points. The contrast of the LCD display is determined by the voltage value on the COM pin minus the voltage value on the SEG pin. When this voltage difference The pixel can be turned on if the saturation voltage of the LCD is greater than the LCD threshold voltage, and the pixel can be turned off. The LCD type MCU has been automatically generated by the built-in LCD drive circuit, so as long as the I/O port can simulate the output of the drive signal , You can complete the LCD drive.
