Design and implementation of intelligent home remote control instrument

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0 Preface

With the rapid development of China's information industry and the increasingly perfect communication infrastructure, intelligent home remote measurement and control systems based on PLMN (land-based mobile communication network) and PSTN (public switched telephone network) can be realized by using existing personal communication terminals. It can save investment and has positive significance for facilitating people's lives, disaster prevention and mitigation. The intelligent home remote measurement and control instrument works on the telephone network. The standard program-controlled exchange signaling (DTMF dual-tone multi-frequency signal, ringing signal, ring-back tone signal, etc.) specified by the Chinese standard is used as the system control command, and the PLMN and PSTN communication network are used. The transmission medium enables the user to remotely control the home appliance equipment by using the fixed-line or mobile phone to send DTMF dual-tone multi-frequency signals at the remote end; at the same time, the system can monitor the home environment and automatically voice dialing alarm.

1 The composition and working principle of the intelligent home remote control instrument

The system can realize individual users to remotely detect and control household appliances, flammable gas concentration parameters, fire conditions, piracy, etc. through information terminals such as mobile phones or fixed telephones, and can work in parallel with ordinary household telephones. The SPCE061A MCU in the hardware part is the core part of the controller. It can receive the user's dialing command to control the home appliance. It can also realize the automatic voice dialing alarm function according to the sampling value of the infrared sensor and the smoke sensor detection circuit. The schematic diagram is shown in Figure 1. The system consists of ringing detection, pick-up control, MT8880 chip, voice playback, home appliance control, infrared sensor and smoke sensor. It is powered by 220V AC, and the battery is used as backup power. The function expansion interface.

Figure 1 Schematic diagram of intelligent home remote control instrument

When the remote control household appliance is needed, the user dials. At this time, the switch sends a ringing signal to the telephone line, and the ringing detection circuit starts ringing detection. The system setting does not affect the normal use of the phone, if the number of rings exceeds the setting. Fixed value, the MCU realizes automatic analog off-hook, then activates the voice prompt module, allowing the user to input the control password. MT8880 decodes the input signal, and sends the decoded output bit code to the MCU to compare with the set password. If the password is verified correctly. (The password is set by the user), the MCU plays the prompt tone, and the user selects the home appliance control key. After inputting the control key, the MCU selects the home appliance to control according to the decoding output of the control key, thereby realizing the purpose of remote control.

The single-chip computer scans the sampling signals of the infrared sensor and the smoke sensor in real time, and continuously compares with the preset alarm value. When the preset alarm value is reached, the MT8880 is set to the transmission mode, the TONE signal is coupled to the telephone line, and the predetermined voice resource is played. The file realizes the automatic dialing alarm function of the single chip microcomputer.

2 DTMF codec implementation

MT8880DTMF transceiver chip. Using the SPCE061A microcontroller to send control timing can easily operate the MT8880.

When MT8880 is used as the DTMF receiver, the signal transmitted from the telephone line is converted into a digital signal by MT8880, and is read by the MCU. The DTMF signal is input through the IN+ and IN- inputs, and the dial tone frequency in the signal is amplified by operation, and then sent to the dual audio filter to separate the low frequency group and the high frequency group signal, and the frequency of the DTMF signal is detected by digital counting. Translated into a 4-bit binary code by a decoder. The 4-bit binary code is latched in the receive data register RDR. At this time, the delay control identification bit in the status register is reset, and the receive data register in the status register is fully marked. Use IRQ/CP as the interrupt signal of the MCU. When the IRQ changes from high level to low level, it sends an interrupt request to the CPU. When the MCU responds to the interrupt and reads the data in the register, the IRQ returns to the high level.

When MT8880 is used as the DTMF transmitter, MT8880 works in burst mode. The MCU will need to send the telephone code to the MT8880 data register, and use TONE to output the dual audio signal and send it through the telephone line. The ringback signal is judged to determine when to send a voice prompt. The circuit for sending and receiving data is shown in Figure 2:

2 DTMF-MT8880 data transceiver circuit diagram

3 SPCE061A microcontroller resource configuration

Sunplus SPCE061A is an on-chip 16-bit single-chip microcomputer with high processing speed and built-in voice recording and playback function. It is very suitable for smart home remote control instrument, which replaces the traditional MCU+voice chip solution and improves reliability. SPCE061A microcontroller has 32-bit programmable I/O port and is rich in resources. Using SPCE061A's DAC1 or DAC2 two audio output channels, plus audio amplifier circuit can achieve automatic voice playback. Table 1 shows the resource configuration of the smart home controller.