10-04-2017, 09:19 PM
Highly distributed data acquisition system provides real-time data
distributed in wide areas at one time, improves the
efficiency of management, and gives lot of
information to analyze. This kind of system can be
This system is a three level hierarchy model. At the top level, there is a master
station which acquires data from multiple slave stations situated in a very wide area. The local slave stations communicate with the master station through SMS Each slave station also acts as a master
in its own local RS485 network to which several
temperature detection modules are connected, these modules are at the lowest level of the hierarchy. It can be imlpmented either based on wired network like internet, or
wireless network such as GSM/GPRS. SMS is a very convenient and
low-cost way of remote data transfer, so it has a great
scope of application.
General structure
1.Central monitor subsystem
it is at the highest level of
the three level-hierarchy model and It mainly consists of an
industrial computer called as the master station, a HMI
(Human Machine Interface) and a GSM interface. This
subsystem gathers information from highly distributed
slave stations in two modes: one acquired as the master station which
queries and the slave stations send back response; and the information slave stations send unasked
during an emergency.
further the data received is processed by the
program running on the industrial computer .doing complicated
analysis, classifying and storing them in different
databases and presenting their tendency in plots.
The
administrator can observe the details of each
slave station, and can send commands to it via the
HMI and GSM interface.
3. Hardware design of the communication
subsystem
Contains an LPC2210 is an ARM7 microcontroller without on-
chip flash memory a 1M*16bit NOR FLASH
SST39VF1601 is used to store code and static data.OS is built in for which its on-chip 16KB SRAM isn't enough, so an extra 256K*16bit SRAM
IS61LV25616AL has been added. A 2kbit I2C
EEPROM AT24C02 is used to store configuration information.
Software design of the communication
subsystem
Software architecture on uC/OS-II
An open-source RTOS uC/OS-II is loaded on
LPC2210 for task management.This is a fully-
preemptive real-time kernel, and is specially designed
for embedded applications, and the source code is very compact.
Communication protocol
A customer-defined communication protocol between the
slave station and the master station is
implemented . The message has a fixed format, and is referred to
as a packet. Each packet is divided into header and data area. Packet carries 160 characters max. Character # is used in Begin of Header and
End of Header fields.