Chapter 8. Advanced Experiments
8.11. Experiment with Wireless Encoding Module
Encoding module has small size and good appearance, widely used in car security system. In this experiment, the encoding module we use has 4 keys, A, B, C, D, which are composed mainly by PT2262 encoding IC and high frequency modulate, and power amplifier circuit. General encoding module looks like the below picture.
PT2262 is a remote control encoder paired with PT2272 utilizing CMOS Technology. It encodes data and address pins into a serial coded waveform suitable for RF or IR modulation. PT2262 has a maximum of 12 bits of tri-state address pins providing up to 531,441 (or 312) address codes; thereby, drastically reducing any code collision and unauthorized code scanning possibilities.
The decoding module contains receiver and decoding IC PT2272.
The receiver send the signal received to 14th Pin (DIN) of PT2272. PT2272 decodes the signal.
PT2272 is a remote control decoder paired with PT2262 utilizing CMOS Technology. It has 12-bit of tri-state address pins providing a maximum of 531,441 (or 312) address codes; thereby, drastically reducing any code collision and unauthorized code scanning possibilities. PT2272 is available in several options to suit every application need: variable number of data output pins, latch or momentary output type.
Generally, we use 8-bit address code and 4-bit data code. The 1 to 8 pin of PT2262 and PT2272 are address pins that are tri-states: 0, 1 or f (floating), providing up to 531,441 (or 312) address codes.
Only when the address code of PT2262 and PT2272 are the same, they can then be matched for communication.
Remote wireless module’s 8 address pin are left floating when it is sold. If user needs to change the address code, set the 8 address pin of PT2262 and PT2272 to the same configuration.
Solder pins to L or H like the below picture.
For most complex system, only one pair of wireless modules is not enough, so MCU must extend for special requirement.
This experiment shows you how to use MCU and wireless module together. Press A, B, C, D keys on the transmitter to send encoded codes. The receiver will transfer its received code to MCU. The codes are then displayed on LED display. When key A is pressed, 0001 will be displayed. When key B is pressed, 0002 will be displayed. So does key C and key D.