Campbell Scientific RF401-series and RF430-series Spread Spectrum Data Radios/Modems - Manual (Page 73)

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
1
2 O TX
3 I RX
4
5 GND
6
7
8 O CTS
9
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, Advanced
Setup Standby Modes), 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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