MSP430F449
Application based on practical granary temperature and humidity measuring system (2)
source: 21IC Author: Wang Mingming, Wang Zhilin, Yuan Hao, pan Hui time: 2012-03-08-
The system adopts the ZigBee protocol to realize wireless communication between devices, data acquisition node is responsible for collecting temperature and humidity data, send data to the routing nodes through wireless module; the router node information on the comprehensive transmits the data to the coordinator; coordinator connected via the RS 232 serial port and PC machine, used to collect the data in the network, and collect the node sends commands and parameters to the data set of information, communication and terminal equipment.
3 hardware design of
Design of />3.1 data acquisition node
each data acquisition node is composed of digital temperature and humidity sensor (SHT11), a data processing unit (MSP430), a wireless transmission module (CC2500) and clock and calendar module (PCF8563), as shown in figure 3.
temperature and humidity sensor SHT11 completed within the region of temperature and humidity information collection and data conversion; data processing unit is responsible for the control of the sensor node operation and data storage; wireless module is responsible for communication with other sensor nodes, calendar clock module provides a time reference for the whole system, at the same time as the data collection to add time mark; energy supply module part of the use of ordinary batteries, providing energy for the various parts of the system.
digital sensor using SHT11 model of temperature and humidity sensor Sensirion Swiss company launched. The chip temperature and humidity sensors, signal amplifying and conditioning, A / D conversion and I2C bus interface. Temperature and humidity data collected, 2 sensitive element chip of the humidity and temperature is converted into an electrical signal, the signal is amplified by the signal amplifier, after 14 bit A / D converter into a digital signal, and then through the I2C bus interface of the digital signal output. Temperature and humidity sensor circuit and MCU SHT11 connection diagram is shown in figure 4.
CC2500 chip
the wireless module is a single-chip transceiver integrated chips produced by Chipcon company, is the industry's smallest, at least one of the power consumption, low cost RF system on chip peripheral elements, at least, the main characteristics of small size, simple peripheral circuit; low power consumption, high sensitivity, adjustable rate; support packet data processing; when the data is received, the information synchronization word automatic detection, address detection, information length analysis and CRC parity function; with WOR function, so that the chip cycle in a deep sleep to wake up, snoop around whether a signal.
Calendar clock module of the PCF8563 is a low power CMOS real-time clock / calendar chip produced by PHILIPS company, through the I2C bus interface is connected with the singlechip, connection diagram shown in Figure 5, can be sent to the MCU current time information, and provide the reference clock signal.
