Modbus – Hardware – RS485 Raspberry Pi HAT

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Informatie (ENG)

The RS422 / RS485 Serial HAT from HWHardSoft is a fully galvanic isolated Serial communication HAT designed for use with the Raspberry Pi. RS485 can be used across large distances, so isolation of the RS485 bus ensures that your Raspberry Pi is fully protected!

RS485 is in use in many applications like industrial and home automation (for example MODBUS), lighting control (DMX), video surveillance (for example Pelco D) and many more!

RS422 / RS485 Serial HAT Features:

  • RS485 mode (half duplex)
  • RS422 mode (full duplex)
  • Galvanic isolation between Raspberry Pi and connected RS485 bus
  • Enhanced ESD protection
  • Adjustable automatic transceiver switching for RS485 mode
  • Adjustable control of transceiver/receiver via GPIO pin
  • Adjustable Pull-Up, Pull-Down und terminating resistors
  • Indicator LEDs for RX and TX
  • Removable block terminal for bus connection
  • Many options adjustable via DIP switches

Foto’s

DIP Switch instellingen

S1 – DIP Switch Configuration – send/receive control:

Channel Description
1 Receiver always on
2 Transmitter connected to Receiver
3 Automatic DE/RE control
4 DE/RE control via GPIO18

S2 – DIP Switch Configuration – RS422/485 mode:

Channel Description
1 Connect Y to terminal K2
2 Connect Z to terminal K2
3 Connect internally Y to A
4 Connect internally Z to B

S3 – DIP Switch Configuration – termination resistors:

Channel Description
1 4k7 Pull-up Resistor on A
2 4k7 Pull-down Resistor on B
3 Not used
4 Terminating Resistor On

Voorbeelden van instellingen

RS422 mode:
SW1 / 1 ON – 2 OFF – 3 OFF – 4 ON (Set GPIO18 to high level to transmit protocols)
SW2 = 1 ON – 2 ON – 3 OFF – 4 OFF
SW3 = 1 ON – 2 OFF – 3 OFF – 4 OFF

RS485 mode:

Send/receive control via GPIO18, no terminating resistor
SW1 = 1 OFF – 2 ON – 3 OFF – 4 ON (Set GPIO18 to high level to transmit protocols)
SW2 = 1 OFF – 2 OFF – 3 ON – 4 ON
SW3 = 1 OFF – 2 OFF – 3 OFF – 4 OFF

automatic send/receive control, multipoint master

SW1 = 1 OFF – 2 ON – 3 ON – 4 OFF
SW2 = 1 OFF – 2 OFF – 3 ON – 4 ON
SW3 = 1 ON – 2 OFF – 3 ON – 4 ON

Schema