RS232/485 Port

There is a simple serial port that supports both RS232 and RS485 modes. The port operates through two signal terminals. In the RS232 mode, these are RX and TX, in the RS485 mode — RX/TX+ and RX/TX-. There is no provision for flow control (RTS and CTS lines are not present), or RS422 interface.

The serial port can be used, for instance, to connect to another IB100x board. In the RS232 mode, the serial port can also be used to update the firmware of the EM1000 module located on the NB10x0 board.

Port lines

Serial port lines are on terminal block #4:

Terminal #	Function
9	Relay 2, normally opened line
8	Relay 2, normally closed line
7	Relay 2, common line
6	Relay 1, normally opened line
5	Relay 1, normally closed line
4	Relay 1, common line
3	Serial port: TX (RS232); TX/RX+ (RS485)
2	Serial port: RX (RS232); TX/RX- (RS485)
1	SYSTEM (COMMON) GROUND

Serial port control

Four lines of the EM1000 module (located on the NB10x0 board) control the serial port:

Line	Function	Corresponding EM1000 I/O	IC1000 cable line
RX (input)	Receive line of the serial port	GPIO8/RX0	17
TX (output)	Transmit line of the serial port	GPIO9/TX0	19
MODE (output)	Mode selection: HIGH - RS485 LOW (or input*) - RS232	GPIO44	14
DIR (output)	Direction control in RS485 mode: HIGH - output LOW - input	GPIO0/RTS0	1

*GPIO line configured as input (default state)

Do not forget to configure the TX, MODE, and DIR lines as outputs. A pull-down resistor on the MODE line ensures that the system boots up with the RS232 port selected.