Specifications
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• Only one device can command the bus, slaves can’t speak with each other
• A device can transmit and receive simultaneously (full duplex)
15.7. Grounding
Although data transmission is balanced in RS-485, a proper grounding may be required if the
distance between devices is long and/or they don’t otherwise share the common ground.
The most common reason for RS-485/422 circuit damages is the excessive potential difference
between the devices. When separate grounding is required connect each remote device to the
common ground wire. Connect the common ground to Arctic’s signal ground (pin 5) and to serial
connector chassis.
15.8. Termination
Usually short lines and small data rates (less than 115200 bps) do not require termination. The
purpose of the termination is to attenuate the reflections on the bus. The value of termination
resistor should match the characteristic impedance of the cable.
Note: The termination causes plenty of load to the bus and increases the idle state power
consumption. It should be used only when required.
16. Testing the solution
The testing procedure below has checkboxes, while following the procedure; you may wish to
check the checkboxes, as you go through the list.
16.1. Testing the console login
For M2M GW, there is a possibility to log in via local keyboard (USB or PS/2) and display (15-pin
sub-D, analog connector) and for Arctic, there is a possibility to use serial console login (RS-232,
19200-N-8-1, crossed cable).
16.1.1. Testing Arctic’s serial connection
1. Check that the Arctic is powered off.
2. Connect a cross-connected serial cable between Arctic and installation computer.
3. In installation computer use e.g. PuTTY or Windows HyperTerminal (Start Æ All
Programs Æ Accessories Æ Communications Æ HyperTerminal).
Use the following settings in HyperTerminal:
New connection name: Arctic
Connect using: <the serial port of the computer, e.g. COM1>
Bits per second: 19200
Data bits: 8
Parity: None
Stop bits: 1
Flow Control: none
4. Switch on the Arctic and wait couple of seconds.
5. You should see the Arctic’s login prompt.
6. Log in as root user, the password by default is empty
Test 1: Test the Arctic login with steps above in order to verify the connection procedure.