Campbell Scientific SDM-SIO1 User Manual
SDM-SIO1 Serial
Input/Output Module
Revision: 7/13
Copyright © 2008-2013
Campbell Scientific, Inc.
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Table of Contents
PDF viewers: These page numbers refer to the printed version of this document. Use the
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1. Introduction.................................................................1
2. Specifications .............................................................2
2.1 Supported Data Rates and Protocols ....................................................2
2.2 Electrical Parameters............................................................................3
2.2.1 SDM-SIO1 Current Consumption.................................................3
2.2.2 SDM-SIO1 Voltage Specifications...............................................4
2.2.3 EMC Compliance..........................................................................4
2.3 Temperature and Humidity Ranges......................................................5
2.4 Physical Parameters .............................................................................5
2.5 Datalogger Compatibility.....................................................................5
3. Installation...................................................................5
3.1 Connections..........................................................................................6
3.2 Safety Considerations...........................................................................8
3.3 Examples for Connecting the SDM-SIO1 to Other Equipment ...........9
3.3.1 RS-485 One to One Connection Example.....................................9
3.3.2 RS-485 Multi Unit / In Line Example.........................................10
3.3.3 RS-485 Half Duplex Wiring Example ........................................11
3.3.4 RS-485 Internal Circuit Diagram ................................................11
3.3.5 RS-232 Wiring Example with Handshaking ...............................12
3.3.6 RS-232 Basic 3-Wire Example ...................................................12
3.3.7 Connecting a 9-Way Socket to the SDM-SIO1...........................13
3.4 Power Conservation ...........................................................................13
4. Programming the Datalogger ..................................14
4.1 Special Information about the Serial I/O() CRBasic Instructions when
used with the SDM-SIO1 ...............................................................14
4.1.1 SerialOpen()................................................................................14
4.1.2 SerialClose() ...............................................................................17
4.1.3 SerialIn() .....................................................................................17
4.1.4 SerialOut()...................................................................................17
4.1.5 SerialInBlock()............................................................................18
4.1.6 SerialOutBlock() .........................................................................18
4.1.7 SerialInChk()...............................................................................18
4.1.8 SerialInRecord()..........................................................................18
4.1.9 SerialFlush()................................................................................18
4.1.10 Serial Input Errors.......................................................................18
4.2 Configuring Handshaking and Receive Only Modes.........................18
4.2.1 Using RTS/CTS and Automatic Handshaking ............................18
4.2.2 RS-485 Half-Duplex Mode.........................................................19
4.2.3 Using the RS-232 Link in Receive Only Mode ..........................19
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Table of Contents
4.3
Example Datalogger Programs.......................................................... 20
4.3.1 Example Using RS-232 Mode.................................................... 20
4.3.2 Example Using RS-485 Mode.................................................... 21
5. Firmware Upgrades and Flash Signature Errors ...22
5.1 Upgrading the Firmware.................................................................... 22
5.2 Firmware Signature Errors ................................................................ 22
Appendix
Using the Handshaking Lines for General
A.
Input/Output ..........................................................A-1
A.1 The Input Pin (Pin 8) ....................................................................... A-1
A.2 The Output Pin (Pin 9) .................................................................... A-2
Tables
3-1. SDM Address Settings ........................................................................ 6
3-2. SDM-SIO1 Connections (left to right as viewed from the front of
the unit)............................................................................................ 7
3-3. SDM-SIO1 Functional Description of the Connections...................... 7
4-1. Communications Port Parameters RS-232 ........................................ 15
4-2. Communications Port Parameters RS-485 Full Duplex .................... 15
4-3. Communications Port Parameters RS-485 Half Duplex.................... 16
4-4. Communications Port Parameters RS-232 Receive Only Mode ....... 16
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SDM-SIO1 Serial Input/Output Module
The SDM-SIO1 Module is designed to allow expansion of the number of serial ports
available on a datalogger for communicating with intelligent sensors or driving external
displays.
1. Introduction
The SDM-SIO1 Module connects to Campbell Scientific dataloggers using the
SDM port and communication protocol. It connects to the remote serial device
using industry standard hardware that can be set to RS-232, RS-485 or RS-422
signal levels. When operating in RS-232 mode it also supports hardware
handshaking. RS-422 mode is functionally the same as RS-485 mode except
the connection is limited to a point to point system. Connections and
programming for RS-422 are otherwise identical to RS-485.
The SDM-SIO1 will accept serial data and store it in its buffer which is 2047
bytes in size allowing remote equipment to transmit large amounts of data
without needing to stop other processes in the datalogger. Up to 15 SDM-SIO1
peripherals can be connected to a single logger using the SDM port, allowing
the user to connect 15 different items of equipment to their logger with ease, in
addition to any connections made to the datalogger’s other serial ports.
To start using the SDM-SIO1 it is first necessary to work out how data will be
exchanged with a sensor. In the case of a sensor there are basically two options,
either the datalogger requests data and then picks up the response, or the sensor
transmits data “one-way” using its own time base. The latter mode is more
common but can lead to problems with synchronizing the sensor measurements
with the logger program and can also lead to the occasional missing data value
as there are two independent clocks. Once the method of communication and
the communication standard is defined then refer to Section 3, Installation, to
install the module and connect it to the datalogger and the serial device.
The SDM-SIO1 Module is implemented in such a way that it looks like a builtin serial port to the user when writing programs in CRBasic. This means all the
user needs to do is define the address of the SDM-SIO1, using a rotary switch
on the side of the unit. The serial port can then be used as if it were built into
the datalogger. The only difference in operation between the SDM-SIO1 and a
built-in port is that there will be a small delay when transferring data to and
from the device via the SDM connection (see Section 4.1, Special Information
about the Serial I/O() CRBasic Instructions).
The SDM-SIO1 can also be used in ‘talk-through’ mode to allow a user to talk,
via a terminal module, to a sensor connected to the SDM-SIO1 for test and
diagnostic purposes. Please refer to the logger manual for further details.
Section 4, Programming the Datalogger, gives the differences in the use of this
module compared to the datalogger standard serial ports, plus there are some
simple examples.
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SDM-SIO1 Serial Input/Output Module
2. Specifications
2.1 Supported Data Rates and Protocols
Data rates and protocols are set up using the SerialOpen() instruction in
CRBasic. The SerialOpen() instruction is discussed elsewhere in this
document.
Supported data rates: 300, 1200, 2400, 4800, 9600, 19200,
Supported modes of operation: RS-232 (full duplex and receive only)
38400, 57600, and 115200 bits/s
RS-485 (half and full duplex)
RS-422 (half and full duplex)
NOTE
NOTE
NOTE
Hardware CTS/RTS flow control is supported in RS-232 mode;
the handshaking lines can also be used as general purpose I/O
lines.
Supported data format: 8, and 7 bit data size; none, odd, or even
parity; one or two stops bits.
In 7 bit mode with no parity the user must insure that the
characters received by the SDM-SIO1 have a delay of at least
one bit period or greater between them. This does not affect any
other configuration and does not affect transmissions out of the
SDM-SIO1.
Transmit buffer size: 767 bytes (buffer from the logger to the
sensor)
Receive buffer size: 2047 bytes (buffer from the sensor to the
logger)
Both transmit and receive buffers are fill and discard type (i.e.,
once the buffers become full no new information is accepted and
all further data is discarded until space is made when the logger
requests data from the SDM-SIO1).
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Miscellaneous information: The SDM-SIO1 does not support auto
baud rate detection nor the use of the serial
port for Modbus, DNP, or general PakBus
communications.
2.2 Electrical Parameters
2.2.1 SDM-SIO1 Current Consumption
Nominal Max Notes
General Currents
SDM-SIO1 Serial Input/Output Module
Standby
current
RS-232 and RS-485 Current Consumption
70 µA 100 µA Current after SerialClose has been
called.
(1)
Idle current 5.5 mA 6 mA After SerialOpen has been called
Idle current
4.1 mA 4.5 mA After SerialOpen in receive only mode
(receive
only)
Active
11.5 mA 12 mA Active RS-232 command
current (RS-
232)
Active
current (RS-
12.5 mA 13 mA Active RS-485 command (no
termination resistors)
485)
Line Load Currents
RS-232 line
load
2 mA per
load
3 mA
per load
Average expected increase in drawn
current per RS-232 line connected in
idle or active modes (no extra current in
stand-by mode).
Both TX and RTS are considered to be
RS-232 loads.
RS-485 line
(2)
load
40 mA
(3)
77 mA
(4)
This extra current is only present when
actively transmitting
(1) All currents are measured with no loads connected
(2) The RS-485 transmit pair is disabled when not transmitting in order to save
power higher value resistors can be used to save power dependent upon the
application. For many applications, especially with shorter cable runs, no
load/termination resistors will be needed.
(3) Single 100R load between transmit lines. Two 100R resistors (one on each
end) is the maximum recommended loading. Removing any termination
resistance should dramatically decrease current consumption during transfer of
data
(4) The RS-485 interface is protected against short circuits via a 44R resistance
making this the maximum current possible even during short circuit. This
resistance is part of the ESD protection circuitry and will be present at all
times; it shouldn’t affect normal circuit operations. The ‘RS-485 internal
circuit diagram’ in Section 3.3.4, RS-485 Internal Circuit Diagram, shows the
circuit in detail.
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SDM-SIO1 Serial Input/Output Module
2.2.2 SDM-SIO1 Voltage Specifications
Connection
Power supply, +12 V
connection
(2)
RS-232 input threshold
Low
RS-232 input threshold
High
RS-232 input absolute
maximum
(2)
RS-232 input
resistance
RS-232 output voltage
(3)
swing
RS-232 output
absolute maximum
RS-485 input
(Differential)
RS-485 output
(Differential)
Minimum
Voltage
(1)
Nominal
Voltage
(1)
Maximum
Voltage
(1)
7 V 12 V 20 V
0.8 V – –
– – 2.4 V
– ±15 V ±18 V
3 kΩ 5 kΩ 7 kΩ
±5 V ±5.4 V –
– – ±13.2 V
200 mV
2 V (at 50
(4)
– 6 V
– –
Ohms)
SDM lines (high level)
SDM lines (low level)
(1) Values are volts D.C. (except resistances)
(2) It is NOT recommended that the user runs their SDM-SIO1 at maximum
ratings for extended periods of time
(3) Assuming a worst case 3 KΩ load
(4) It is not recommended that the user allows such low input voltages as there
will be an increased chance that external noise may cause errors in the
incoming data
2.2.3 EMC Compliance
The SDM-SIO1 has been tested and shown to comply with IEC 61326. The
device incorporates transient and surge protection that is designed to meet
IEC61000-4-5, level 4, providing the device is adequately grounded.
4.3 V 5 V 5.7 V
0 V – 0.7 V
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SDM-SIO1 Serial Input/Output Module
2.3 Temperature and Humidity Ranges
Temperature
Range
Standard range –25ºC +50ºC
Extended range
(optional)
Humidity Minimum Maximum Notes
Standard range 0% 95% (non-condensing)
2.4 Physical Parameters
Height: 5.4 cm (2.2 in)
Width: 8.0 cm (3.1in) main body; 11.2 cm (4.5 in) with mounting flange
Depth: 2.5 cm (1.0 in)
Weight: 80 g (2.8 oz) approximately
Mounting: Centers are 10.2 cm (4 in)
Minimum Maximum Notes
–40ºC +80ºC (Contact Campbell Scientific
for further extended
temperature requirements)
2.5 Datalogger Compatibility
3. Installation
The SDM-SIO1 is compatible with our CR800, CR850, CR1000, CR3000,
CR5000, and CR9000X dataloggers. The CR5000 and CR9000X’s operating
system must be OS 6 or higher.
The SDM-SIO1 is normally mounted on the backplane of a Campbell
Scientific enclosure using the screws and plastic inserts provided. The SDMSIO1 is designed to be installed in a dry, non-condensing environment. Before
fixing it, select and set the SDM address as this requires access to the side of
the case. The SDM address is set with a screw driver. Below is a list of the
possible SDM addresses and their relationships to the COM port number in the
SerialOpen() instruction.
There can be up to 15 SDM-SIO1s on a single SDM bus. Each SDM-SIO1 will
need to have a unique address before they are powered up. If other equipment
is present on the bus, whether it’s an SDM-SIO1 or not, the user needs to
insure no addresses are the same.
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