4 TWN4 Palon One PCB
4.3 DIP Switch and Main Connector
While the module can be connected via USB port, its main host connection is RS485. The RS485 interface
is accessable via X2. Table 4.1 shows the pinout of X2, figure 4.2 shows the polarity of the pins.
Pin
Name
1
RS485_A
2
RS485_B
3
D0 or DATA
4
D1 or CLK
5
GND
6
UIN
Table 4.1: X2 Pinout
For RS485, the address of each module must be adjustable. This can be done with the DIP switches. Fur-
thermore, the RS485 bias and termination can be set. Table 4.2 shows the assignment of the DIP switches.
DIP
Assignment
1
RS485 address 0 (LSB)
2
RS485 address 1
3
RS485 address 2
4
RS485 address 3 (MSB)
5
RS485 bias
6
RS485 baud rate (LSB)
7
RS485 baud rate (MSB)
8
RS485 Termination 120 Ohm
Table 4.2: DIP switches
The behaviour of the DIP switches 1-7 is controlled by firmware and may change in future.
When switch 5 / RS485 bias is switched on, a pull-up resistor is connected to RS485_A and a pull-down
resistor is connected to RS48_B signal. This prevents an undefined state of the bus when no transmitter
is active.
Switch 8 / RS485 Termination 120 Ohm connects a 120 Ohm resistor between RS485_A and RS485_B
signal, which prevents reflections on the bus.
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