User manual

464
mikoC PRO for dsPIC
MikroElektronika
HW Connection
PWM Motor Control demonstration
RS-485 Library
RS-485 is a multipoint communication which allows multiple devices to be connected to a single bus. The mikroC PRO
for dsPIC30/33 and PIC24 provides a set of library routines for comfortable work with RS485 system using Master/
Slave architecture. Master and Slave devices interchange packets of information. Each of these packets contains
synchronization bytes, CRC byte, address byte and the data. Each Slave has unique address and receives only
packets addressed to it. The Slave can never initiate communication.
It is the user’s responsibility to ensure that only one device transmits via 485 bus at a time.
The RS-485 routines require the UART module. Pins of UART need to be attached to RS-485 interface transceiver,
such as LTC485 or similar (see schematic at the bottom of this page).
Library constants:
- START byte value = 150
- STOP byte value = 169
- Address 50 is the broadcast address for all Slaves (packets containing address 50 will be received by all Slaves
except the Slaves with addresses 150 and 169).
Important :
- The library uses the UART module for communication. The user must initialize the appropriate UART module before
using the RS-485 Library.
- For MCUs with multiple UART modules it is possible to initialize them and then switch by using the UART_Set_Active
routine.