MCU-based remote control software PT2262 Encoder Decoder
PT2262 is a infrared remote control encoder, PT2272 is a decoder to receive the two pairs are often used, is now widely used in automotive door control, remote control door locks, access control management, but also can be used for transmission of digital information. PT2262 with 19 binary coding function; PT2272 decoder only 4 to 6, which limits the data transmission applications. PT2262 receive this from the start of the signal characteristics, the use of single-chip direct 8051F330 docking decode the signal received, PT2262 issued to explain all the 19 data, so that it applies to digital communication, intelligent control.
2 hardware circuit
Figure 1 is a schematic diagram of the launcher, PT2262 as the encoder, when press the button, set the address code and data code from the 17-pin serial output, the infrared emission signal components IRED. Section through the firing resistor Rosc wither frequency PT2262 to increase operating voltage (2.6 V ~ 15 V), in order to increase the launch distance. A0 ~ A12 which can be set to high, low, left three states, it can send 531,441 kinds of code combinations, fully meet the design requirements.
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Set the use of infra-red receiver for receiving, amplification, plastic integrated circuits in one of the TL0038, without any external components, can be done to the output from the infrared receiver with TTL-level signal compatible with all the work, it applies to all kinds of infrared remote control and infrared data transmission. 8051F330D the use of single-chip decoder, 11.0592MHz crystal oscillator, receiving the signal sent to the I / O port P1.0 software decoder. Receiving and decoding circuitry as shown in Figure 2.
Principle 3 decoder
PT2262 encoder encoded signal is sent from: address code, data code, synchronization code comprising a complete code word can have up to 12 (A0 ~ A11) end a three-state address pins (left, high and low level), any combination of available addresses code 531 441. PT2262 to the A8 encoder push, D3 raised, D0 raised, D1 down, and the remaining vacant. Interception of a period of output waveform of the signal receiver module as shown in Figure 3, PT2262 each fired once, sending at least 4 groups code the same code. Each code interval (low level) of about 14 ms.
To each code waveform intercepted amplification, as shown in Figure 4, a group of code there are 12 A / D code, each A / D are expressed by the two pulses: two narrow pulse that "0" ; 2 wide pulse that "1"; a narrow pulse and a pulse width that the "F" that is, the address code "vacant"; In addition, each code there is a synchronization between the code separated Therefore, each code width of a total of 25 different pulse. Narrow pulse width 200μs, pulse width of 1 200μs; between two narrow pulse width l 200μs; two pulse width Q 200μs; width between pulse width 200μs; in the 4 groups in the code, each code interval is 14 000μs. Therefore, the use of single-chip decoding software, as long as the start code to determine and identify the code behind the pulse width can be.
4 anti-interference measures
Commonly used anti-interference measures is the use of hardware circuits in power filtering, power regulators, digital and analog isolation. In design, with the exception of the use of the above-mentioned methods, also based on signal interference and signal similarities and differences between waveform characteristics, the use of software to identify interference signals and the effective signal to achieve the "anti-" purpose.
When the remote control does not launch, due to the air of the clutter interference, the signal receiver module and there will still be interference output signal, intercepted waveform shown in Figure 5.
Observe the characteristics of low-level up to 3 000 μs, the minimum scores of microseconds; high up 500μs, the minimum number of microseconds. With the launch of the rules received waveform (that is, non-valid signal) compared to low-level signal for the 1 400μs is an effective signal, rather than interfere with the signal.
And address A0 ~ A34 soldered to the high signal as the launch of the frame before coding code error rate and 10 to address the issue of interference.
5 software decoder
Step 1: Single-chip receiver module cycle record level signal pulse length, high-low-level are recorded.
Step 2: from the record high in the low-level components of the waveform to identify eight consecutive hours 1200μs long pulse waveform is characterized by, that is, before the code frame.
Step 3: Verify code before the pre-frame whether or not there is a long time for the low 14000μs, if there (is that not interfere with code), to decode and store the results, and then follow the instructions to implement the corresponding control code. If not, then give up the record data, repeat Step 1 until the date to meet the conditions.
The following gives the decoding software program code:
Part of the software decoder 8051F330D single chip in (11.059 2 MHz crystal oscillator) through field testing, the design can be applied to access control management system. Practice shows that the application of the convenience, reliability, and accurate identification code.
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