This is a design circuit that can be used to convert a standard LCD interface parallel to serial interface model, use a microcontroller or a dedicated circuit such as the MIC 702 Mictronics you can download the complete data sheet and French by clicking this link. This is a circuit specially designed to transform the parallel interface and LCD display logic integrated asynchronous serial interface standard. This is the figure of the circuit;
The MIC 702 is connected directly to the display with which it is perfectly compatible. Notice the connection with only 4 data bits of high weight since the MIC 702 operates in the display mode twice 4 bits. PC side, the connection with the serial output of the PC does not involve any level converter for RS 232 TTL, this role being played by the only resistor R1 22 ohm whose presence is essential. BAUD The tab allows you to choose the operating speed of the circuit between two speeds: 9600 bps up with S1 or S2 with 2400 baud up. The leg POL allows the circuit to interpret the serial data as direct or inverted. As it is in direct RS232 link should be link this foot to ground to indicate the MIC 702 that receives data reversed. Linkage to +5 volts it would receive direct evidence as would be the case if we wanted to use this circuit with a Basic Stamp example.
Subject to use a display not backlit, the total consumption of the circuit is low enough that it can take its power directly from the output control signals to the RS 232. It is the role of diodes D2 and D3 associated with IC1, which is a regulator with low dropout voltage and low consumption. If you insist on using a backlit display, it is possible that consumption of its single backlight exceeds the possibilities of the PC's serial port. You can use an external power supply via the diode D1. A voltage of 9 volts at a flow rate of a hundred mA appropriate.
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