At present, a large number of daily appliances are used in people’s home life, but these daily appliances need to be directly controlled by people. Although they can be controlled at certain times, their functions are limited and their flexibility is poor. As mobile terminals continue to become popular, developing their extended applications will have a broad equipment foundation and broad market prospects. By relying on the public information network, mobile terminals can be used to control household appliances and inquire about home conditions. This article discusses an attempt to combine information processing technology with device control to achieve digital homes, allowing people to enjoy the convenience brought by the information revolution to their lives. The innovation of this article lies in using ZigBee technology for home networking combined with DSP technology and SMS to achieve communication between remote devices and users. This way, the network has a wide coverage range, which has advantages such as no need for dialing, low cost, and wide coverage when controlling and monitoring. Moreover, there is no need to reconfigure the power grid, which can save financial, material, and human resources, and is stable, reliable, and easy to implement.
2 System Hardware Design
The smart home system has functions of remote control, remote query, and centralized management of various devices in the home. IS2020RKPSG3A provides users with a more comfortable and convenient lifestyle. This design is mainly aimed at home appliance control. The ZigBee communication sub node needs to have functions such as pulse data acquisition, switch data acquisition, analog data acquisition, relay contact output, etc. The main node is actually a fully functional FFD device that manages the home subnet node and communicates with the home server to achieve information exchange between the server and sub nodes. In this design, the home internal node is mainly composed of the RF chip CC2430 and the TMS320VC5402 chip. CC2430 is a ZigBee wireless network module that complies with the IEEE 802.15.4 standard (MAC, and PHY layers). The TMS320VC5402 chip is used to control the operation of the CC2430ZigBee module and is connected to the GSM module through MAX3111 for data communication. We will integrate ZigBee’s coordinator node and GSM module into one board. Nodes are in a sleep state during idle time. When users have control signals or data collection requirements, interrupts are used to wake up the nodes, complete data collection or control tasks, and report relevant information.
The system composition diagram is as follows:
The main control center module is responsible for receiving SMS, judging commands, issuing or directly driving execution commands, and sending the working status of the machine to the mobile terminal via SMS.
This type of work can use a low-priced ordinary C51 microcontroller. However, considering the need to expand the application of image-based multimedia message feedback in the future, the processor of the controller in this design uses the TMS320VC5402 chip for IS2020RKPSG3A. The DSP main control module uses a TMS320VC5402EVM evaluation board and simulator. The TMS320VC5402EVM provides two BCMSP direct connection ports J6, J7, and PHI driver ports J2 and J5 for interface connection with the simulator. This board has 512KRAM data storage and 64KRAM as program storage. 4KFLASH memory can be used to store data that needs to be retained.
To connect with the GSM module, TMS320VC5402 needs to expand the RS232 interface. TMS320VC5402 only provides two multi-channel buffered synchronous serial ports MCBSP0 and MCBSP1. If docking is implemented, it is necessary to convert the MCBSP serial port. We are using the MAX3111 chip here. The MAX3111 chip has the characteristics of small size, low price, low power consumption, and high communication speed. Realize the conversion from synchronous serial data interface to asynchronous serial port (RS-232) using MAX3111 chip. Can be connected to the RS232 port of H6221. MAX3111 consists of two parts: UART and RS-232. The UART part includes a SPI compatible serial port, a programmable baud rate generator, a transmit buffer and transmit shift register, a receive buffer, a receive shift register, an 8-byte receive FIFO, and an interrupt generator with four maskable interrupt sources. The RS232 part includes an electric pump with built-in capacitance.
Due to MAX3111 being a 3.3V device, the MCBSP serial interface of TMS320VC5402 can be directly connected to MAX3111 in SPI mode to achieve asynchronous data transmission with RS232 devices. At this time, TMS320VC5402 serves as the main device in the SQI protocol, sending a time-resolved signal (BCLKX) as the serial time-resolved input for MAX3111, and sending a frame synchronization signal (BFSX) as the original selected signal (TCS) for MAX3111. BDX is connected to DIN as a data transmission cable. BDR and DOUT serve as receiving data lines.
The function of MAX3111 can be customized by sending 16 bit control word configuration commands to it through BDX cable. The TX of MAX3111 is connected to T1IN, while the RX is connected to R1OUT to facilitate UART to RS232 level conversion using its on-chip converter.
The MAX3111 serial interrupt signal (IRQ) is connected to the external interrupt LNTO of the DSP. This eliminates the need for any other peripheral devices. Due to the implementation of asynchronous transmission and reception by MAX3111 hardware, the software programming of TMS320VC5402 only needs to consider synchronous data communication with MAX3111.
The connection between TMS320VC5402 and CC2430 is the execution link of the system. Due to the fact that CC2430 is based on C51, the connection between TMS320VC5402 and CC2403 is similar to that of a C51 microcontroller, except that the level of CC2430 is 2-3.9 volts.
The interface level of TMS320VC5402 is 3.3 volts, which can be directly matched, reducing the trouble of level conversion.