Hardware Development

• The system development was focused separately in terms of :

                  i.            Hardware design
                              ii.            Software design

• PIC 16F877A Circuits:

 

 

 

• RS-232 Data Interface:

A DB-25 connector as described in the RS-232 standard

RS-232 is simple, universal, well understood and supported but RS-232 has some serious shortcomings as a data interface. The standards for RS-232 and similar interfaces usually restrict RS-232 to 256kbps or less and line lengths of 15M (50 ft) or less but today we see high speed ports on our home PC running very high speeds and with high quality cable maxim distance has increased greatly. The rule of thumb for the length a data cable depends on speed of the data, quality of the cable.

  

PC Com Port - EIA-574 RS-232 pin out DB-9 pin used for Asynchronous Data

• MAX-232: 

 

MAX-232 Chip

The MAX232 IC is used to convert the TTL/CMOS logic levels to RS232 logic levels during serial communication of microcontrollers with PC. The controller operates at TTL logic level (0-5V) whereas the serial communication in PC works on RS232 standards (-25 V to + 25V). This makes it difficult to establish a direct link between them to communicate with each other.

 

 

MAX-232 schematic circuit