The repeater of serial communications
based on PIC16F74 microcontroller
Abstract
At present,the monitoring system is ubiquitous. The work of monitoring is decentralized and the management of the monitoring results is centralized. This is so-called distributed control. To connect the scattered nodes, the simplest way is to use serial bus architecture.
In the field of multi-machine communication, MCU have a flexible and efficient multi-machine communication function, so its application is more and more extensive. But, because the SCM signal are TTL level, the limited capacity of driver and anti-jamming, in Practical application, used with other bus.RS485 bus is one of them. RS485 bus is the balance differential transmission, and have good anti-jamming. The farthest transmission distance is 1200 m. It can diver as many as 31 * 31 SCM, which very suitable for the multi-communication system.
RS485 Serial communication system is half-duplex, and the host MCU can control other MCU, which is mainly responsible for monitoring or controlling the decentralized electronic equipment,and receive orders from the host machine to make the appropriate answer.
In the design, CPU adopts the Microchip 8-bit processor PIC16F74.Because the MCU is highly integrated, the external circuit can be simplified .The price of pic16f74 is low.So the system is higher efficient, reliable and economical.
The difficulty of this issue or the key point is the software, which is to guarantee the orderly conduct of communications.So the strict and perfect communication protocol is the need.
The design not only can solve the distribution of monitoring, but also can solve transmission error problems in the long-distance, and can expand communication distance.
In this paper the actuality of the repeater of serial communications, brief of PIC MCU, RS485 communications, HT1621LCD, 4 * 4 keyboard, the expanded data storage and power modules and various modules Software design.
