NCD RS-485, Руководство пользователя, Страница: 3 / 11

available, allowing you to adapt the module in a number of ways. NCD Node modules are preconfigured for RS-
485 communications at 9600 baud. Node modules communicate to the host device at 57.6k baud by
default. Baud rate settings are programmable via RS-485. The C jumper must be installed for
configuration. The node module must power-up with the C jumper installed. Similarly, once configuration is
complete, the node module must be powered up with the C jumper removed for proper operation.
RS-485 Node Module Hardware Description
The NCD Node Module has a Atmel processor and one RS485 transceiver (SN65HVD12D). The On board
processor has 2 USARTS. One USART is connected to the RS-485 trans receiver and the other USART
communicates to the host device. NCD RS-485 node modules operate at 3.3V DC. This communications
module includes bus pin short protection from -7V to 12V DC and 16kV ESD protection. Up to 256 nodes
may be connected on the bus simultaneously. For longer communication distances, low baud rates (such as
9600 baud) are recommended.
NCD RS-485 node modules act as RS-485 to USART converter. Since USART communications is available on
most computing platforms, it’s possible for most computing devices to communicate via RS-485 with the correct
adapter.

Raspberry Pi 2 and 3 to Modular Communications Adapter allows RS-485 communications with a Raspberry Pi 2
or 3

Arduino to Modular Communications Adapter allows RS-485 communications with Arduino Uno

Particle Photon to Modular Communications Adapter allows RS-485 communications with a Particle Photon

Particle Electron to Modular Communications Adapter allows RS-485 communications with a Particle Electron

BeagleBone Communications Adapter allows RS-485 communications with a BeagleBone White or Black

Onion Omega to Modular Communications Adapter allows RS-485 communications with Onion Omega 1 or 2
RS-485 Node Jumpers
Be sure to install jumpers, then power-up the module. Module must be power-cycled anytime the jumpers are
changed. Jumper settings only take effect on power-up.
1, 2, 3 Jumpers: RS-485 Bus Termination

Set J3 Jumper when the node device is the first device on the bus.

Remove all jumpers when the device is in between the first and last device on the bus.

Set J1, J2, and J3 when the device is the last or only device on the bus.
BR Jumper

The BR jumper is not currently used in this design, but is reserved for future use.
C Jumper: Configuration Mode
This jumper is used to put the module in configuration mode. This jumper must be installed to change the baud
rate. Be sure to power-cycle the module after any jumper change. Jumper settings are read during power-up
only. Use the RS-485 port to write configuration data into the module. The RS-485 baud rate in configuration
mode depends on the settings stored in the module. You may test the baud rate using the read commands
below.