Mikroelektronika MIKROE-442 데이터 시트
440
mikoBasic PRO for dsPIC30/33 and PIC24
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. mikroBasic 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.
if (current_duty > pwm_period) then ‘ If we decrease current_duty greater then
possible pwm_period value (overflow)
current_duty = pwm_period ‘ set current_duty to max possible value
end if
PWM1_MC_Set_Duty(current_duty, 1) ‘ Set newly acquired duty ratio
end if
Delay_ms(5) ‘ Slow down change pace a little
wend
end.