Specifications

SDM-SIO1 Serial Input/Output Module

Enabling handshaking will increase active current consumption due to the extra

RS-232 load. It will not affect sleep current however as the RS-232 chip is

disabled (sleep is set by calling the ‘SerialClose’ function).

For connection diagrams and further information on using handshaking consult

section 3.3 within this manual.

NOTE

• Auto flow control should only be selected in RS-232 mode

• When Autoflow control is enabled the user can’t set or clear

the spare I/O ports (pins 8 and 9)

4.2.2 RS-485 Half-Duplex Mode

In RS-485 half duplex mode the SDM-SIO1 will wait for approximately 2.5 ms

after a character is received before it tries to transmit data in the transmit

buffer. This is to insure that a contention does not occur on the data line which

will cause data corruption.

When in either RS-485 half duplex or full duplex modes the user

can’t set or clear the spare I/O ports (Pins 8 and 9).

NOTE

4.2.3 Using the RS-232 Link in Receive Only Mode

To place the SDM-SIO1 into RS-232 receive only mode, use the ‘SerialOpen’

command with the ‘SerialOpenFormat’ value set within the range of 64 to 79.

Consult section 4.1.1 in this manual for more detailed information about these

settings. In receive only mode the SDM-SIO1 will consume less current than

normal but still can receive new information on its RS-232 port.

The example below will set the SDM-SIO1 with the address 0 into receive only

mode. All normal baud rates and buffer sizes are supported.

Example

SerialOpen (32,115200,64,100,10000) ‘Set receive only mode

4.3 Example Datalogger Programs

Some simple examples of how to write programs in CRBasic to send and

receive data using the SDM-SIO1 follow. These programs are not extensive

and are fundamentally no different to those written for use when reading data

from a standard serial port.

The exact program to be used will vary with the serial device being used.

Unfortunately the number of possible variations of reading different sensors is

almost infinite. If you are struggling to write code please contact Campbell

Scientific who may already have experience with the sensor and may be able to

offer advice on how to deal with it.