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Appendix E. Port Pin Descriptions

RS-232 Port

The “RS232” port is a partial implementation of RS-232C. It is configured as

Data Communications Equipment (DCE) for direct cable connection to Data

Terminal Equipment (DTE) such as an IBM-PC serial port.

RS-232 CONNECTOR, 9-PIN D-SUB FEMALE

PIN I/O DESCRIPTION

2 O TX

3 I RX

5 GND

8 O CTS

I = Signal Into the radio, 0 = Signal Out of the radio

Only CTS is implemented for flow control. If data arrives (say from a PC)

faster than the radio transmits it, the radio will de-assert CTS when the 640

byte port buffer is full. If the PC continues to send data, the buffer will accept

it and may wrap around over-writing oldest data. LoggerNet monitor CTS to

prevent buffer over-run.

The radio can transmit RF packets slightly in excess of 9600 baud. When RF

packets are received by the radio, that data is immediately sent to the “active

interface” port without flow control (no RTS).

For many applications, the radio works fine with no flow control. The need for

flow control arises when longer standby modes are used, where more data

could be sent than the 640 byte buffer can hold before transmittal. For

example, if the radios are in Standby Mode 6 (see Appendix B.4), the radio

needs to buffer incoming RS-232 data for up to 8 seconds while waiting for

the other radio to wake up before transmitting it. Also, if the radio is doing a

lot of retries, that can take extra time and require flow control to avoid buffer

over-run.

CS I/O Port

The RF401’s CS I/O port is Campbell Scientific's input/output port. It is not a

standard RS-232 pin-out. The following table provides pin-out information on

the port when connected to a datalogger.

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Campbell RF400 Handbuch Seite 73