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RS485 port on Sequent Microsystems cards for Raspberry Pi

Posted by Mihai Beffa on

All the Sequent Microsystems cards with the exception of the Home Automation have an RS485 transceiver wired to a pluggable connector. The cards fall into two categories: Smart (with local processor) or Dumb (using I/O expanders). 

Using the RS485 port on the Smart cards

On the Smart cards (Industrial and Building Automation, and RTD Data Acquisition), a 2 section jumper permits connecting the RS485 port directly to the processor or to Raspberry Pi.
RS485 Jumpers
To use the port from Raspberry Pi, perform the following steps:
  1. Install two jumpers to route the RS485-TX and RS485-RX from the line driver to Raspberry Pi GPIO connector
  2. Disable the RS485 port on the local processor
  3. Activate the serial port on Raspberry Pi from raspi-config command.
  4. Install an USB to RS485 adaptor on your PC.
  5. Install a terminal emulator program on your PC.
  6. Click HERE to download a Python script to test the communication.

 You can also use the RS-485 port from the local processor, by removing the jumpers and using the following commands:

 Using the RS485 port on the Dumb cards

On the Dumb cards (8-RELAY, 8-MOSFET, 8-INPUTS, 4-RELAY/4-INPUTS and 16-INPUTS) the RS485 port is connected directly to Raspberry Pi serial port. The RX line is separated by a single jumper, labeled either RS485 or RXD. Install the jumper if you want to use the RS485, remove it if you need to use the RXD pin as GPIO


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