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SDM-SIO1A and SDM-SIO4A Serial Input/Output Modules

6.3 Programming

The normal serial port instructions such as

SerialOpen()

and

SerialIn()

are

used with the SDM-SIO1A. Aside from changes to the

COMPort

and the

SerialOpenFormat

parameter, a program written for a standard serial port will

usually work with the SDM-SIO1A. The main difference to be aware of, when

trying to write fast running programs, is the extra delay needed to transfer data

from the SDM-SIO1A to the datalogger (roughly equivalent to transferring

data over a serial link at 38 kilobaud).

The following section gives further information about the CRBasic

programming language and how the serial instructions are to be used with the

SDM-SIO1A.

This section assumes the user has knowledge of the CRBasic programming

language. A useful introduction to programming for serial sensors can be found

here:

https://s.campbellsci.com/documents/sp/technical-papers/serial.pdf

Please contact Campbell Scientific for further assistance or training. Campbell

Scientific’s user forum is also a useful resource to check if others might have

already written code for a specific serial device.

Only the parameters that need special explanation or whose functionality has

changed when used with the SDM-SIO1A are listed below. Any other

parameters should be taken as not having changed. Please refer to the

datalogger manual and/or the

CRBasic Editor

help system for more guidance.

6.3.1 CRBasic Instructions

6.3.1.1 SerialOpen()

All internal buffers in the SDM-SIO1A will be flushed when this instruction is

called, resulting in the loss of any data that might have been in them at that

point in time.

•

COMPort

The

COMPort

numbers are defined in TABLE

6-1

SDM Address Settings

(p. 9)

. COM port numbers in the range of 32 to 47 are reserved for use with

the SDM-SIO1A.

•

BaudRate

is used to set up the SDM-SIO1A baud rate as you would with

any RS-232 interface. The SDM-SIO1A does not support automatic baud

rate recognition. Instead, setting the rate to a negative number sets the

automatic flow control system (RTS/CTS). This system is discussed in

greater detail in Section

7.1.1

Using RTS/CTS and Automatic

Handshaking

(p. 23)

•

SerialOpenFormat

This parameter sets the data format. It also determines whether the

SDM-SIO1A works in normal RS-232, listen-only RS-232, full-duplex

RS-485, or half-duplex RS-485 mode as defined in the tables below.

Содержание SDM-SIO1A

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Страница 3: ...s under guarantee or not Please state the faults as clearly as possible and if the product is out of the guarantee period it should be accompanied by a purchase order Quotations for repairs can be given on request It is the policy of Campbell Scientific to protect the health of its employees and provide a safe working environment in support of this policy a Declaration of Hazardous Material and De...

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Страница 5: ...s digital cell phones and aerials may also not be applicable according to your locality Some brackets shields and enclosure options including wiring are not sold as standard items in the European market in some cases alternatives are offered Details of the alternatives will be covered in separate manuals Part numbers prefixed with a symbol are special order parts for use with non EU variants or fo...

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Страница 7: ...fore beginning work Wear a hardhat and eye protection and take other appropriate safety precautions while working on or around tripods and towers Do not climb tripods or towers at any time and prohibit climbing by other persons Take reasonable precautions to secure tripod and tower sites from trespassers Use only manufacturer recommended parts materials and tools Utility and Electrical You can be ...

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Страница 9: ...1 Mounting 8 6 2 Connection and Wiring 9 6 2 1 Wiring Examples for Connecting the SDM SIO1A 11 6 2 1 1 RS 485 RS 422 Full Duplex One to One Connection Example 12 6 2 1 2 RS 485 Full Duplex Multi drop Example 12 6 2 1 3 RS 485 Half Duplex Wiring Example 13 6 2 1 4 RS 232 Wiring Example with Handshaking 14 6 2 1 5 RS 232 Basic 3 Wire Example 14 6 2 1 6 Connecting a 9 Way Socket to the SDM SIO1A for ...

Страница 10: ...The Input Pin CTS Pin 11 A 1 A 2 The Output Pin RTS Pin 8 A 2 B Matching SDM SIO1A Connections to an SDM SIO1 B 1 Figures 1 1 SDM SIO1A Serial Input Output Module 1 7 1 RS 485 Internal Circuit Diagram 25 Tables 6 1 SDM Address Settings 9 6 2 SDM SIO1A Terminal Labels and Functions 10 6 3 SDM SIO1A Functional Description of the Connections 10 6 4 Communications Port Parameters RS 232 17 6 5 Communi...

Страница 11: ...t labelling for some terminals see Appendix B Matching SDM SIO1A Connections to an SDM SIO1 p B 1 for more details of the differences FIGURE 1 1 SDM SIO1A Serial Input Output Module The SDM SIO4A module is functionally the same as four SDM SIO1As fitted inside in a compact case providing four serial ports The SDM SIO4A is used in the same way as the SDM SIO1A and uses the same CRBasic code in the ...

Страница 12: ...small and excessive current will not flow between the two ground wires There is a current limiting resistor fitted in the RG line in the SDM SIO1A but this will not be adequate in the event of a serious ground fault for example the ground references being 240 V apart due to faulty AC wiring If a large potential difference is found please seek the advice of a qualified electrician before continuing...

Страница 13: ...s The SDM SIO1A will accept serial data and store it in its buffer allowing remote equipment to transmit large amounts of data without needing to stop other processes in the datalogger whilst the data is received The SDM SIO1A connects to the datalogger via three digital lines using a proprietary protocol called SDM It connects to the remote serial device using a standard serial interface that can...

Страница 14: ... one or two stops bits In 7 bit mode with no parity the user must ensure that the characters received by the SDM SIO1A have a delay of at least one bit period between them This does not affect any other configuration and does not affect transmissions out of the SDM SIO1A Miscellaneous information The SDM SIO1A does not support auto baud rate detection or use of the serial port for general PakBus c...

Страница 15: ...en actively transmitting 1 All currents are measured with no loads connected For the SDM SIO4A the currents quoted need to be totalized to allow for the state of each active serial port 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 cabl...

Страница 16: ...es are dc 2 It is NOT recommended that the user run their SDM SIO1A 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 View the SDM SIO1A EU Declaration of Conformity at www campbellsci eu sdm sio1a View t...

Страница 17: ...s more than one SDM device After mounting as close to the datalogger as possible to minimize the cable runs the interface is connected to the datalogger SDM and power connections Refer to Section 6 2 Connection and Wiring p 9 for further details Study the documentation of the serial device you want to connect to the SDM SIO1A to determine the most appropriate method of connection for the applicati...

Страница 18: ... specify which serial port the speed and mode of operation The speed is set by the BaudRate parameter in the instruction and the mode bits parity duplex RS 232 or RS 485 is set by the SerialOpenFormat parameter Refer to the CRBasic Editor help system for more details of the options With the correct parameters in the SerialOpen instruction the program can be written in almost exactly the same way a...

Страница 19: ...to E 14 only port 1 could be used as sequential addresses above that are not valid TABLE 6 1 SDM Address Settings Rotary Switch Position SDM Address SerialOpen Instruction COMPort Number 0 0 32 1 1 33 2 2 34 3 3 35 4 4 36 5 5 37 6 6 38 7 7 39 8 8 40 9 9 41 A 10 42 B 11 43 C 12 44 D 13 45 E 14 46 F1 151 471 1 Address F is not available as it is the broadcast address Setting this address will result...

Страница 20: ...232 RTS RS 485 half duplex non inverting RS 485 full duplex outgoing 9 Tx TD RS 232 transmit RS 485 half duplex inverting RS 485 full duplex outgoing 10 Rx RD RS 232 receive RS 485 receiver non inverting RS 485 full duplex incoming 11 CTS RD RS 232 CTS RS 485 receiver inverting RS 485 full duplex incoming 1 Connection RG pin 6 has a 100 Ω resistor in series with the datalogger ground connection Th...

Страница 21: ...tion of the serial device taking into consideration issues such as power consumption cable lengths RS 485 being better than RS 232 for long cables synchronization of data collection etc If possible use screened cable for connecting the SDM SIO1A to remote sensors or devices Check the manual of the device for details on where to connect the screen for maximum effectiveness RS 422 mode is functional...

Страница 22: ...SDM SIO1A and SDM SIO4A Serial Input Output Modules 12 6 2 1 1 RS 485 RS 422 Full Duplex One to One Connection Example 6 2 1 2 RS 485 Full Duplex Multi drop Example ...

Страница 23: ...ex Wiring Example This shows how to connect a single device but RS 485 half duplex networks are the most common multi drop configuration If wiring for multiple devices make the three wire connections in parallel similar to that shown in the full duplex multi drop example As with all RS 485 configurations the use of termination resistors is optional They tend not to be required with shorter cable r...

Страница 24: ... 4 RS 232 Wiring Example with Handshaking DTE DCE Note CTS and RTS are optional if hardware handshaking is not required Not connecting the handshaking lines will reduce the overall current consumption of the SDM SIO1A 6 2 1 5 RS 232 Basic 3 Wire Example DTE DCE ...

Страница 25: ...e or female connector before making up this cable Pin 8 Pin 2 Pin 3 Pin 7 In RS 232 mode the main use of the CTS RD and RTS TD lines is as RTS CTS hardware handshaking lines CTS RD should be connected to the remote equipment s RTS and RTS TD to its CTS line The CTS RD CTS and RTS TD RTS lines can also be used to trigger external circuitry when not being used in handshaking mode Note that when usin...

Страница 26: ...already written code for a specific serial device Only the parameters that need special explanation or whose functionality has changed when used with the SDM SIO1A are listed below Any other parameters should be taken as not having changed Please refer to the datalogger manual and or the CRBasic Editor help system for more guidance 6 3 1 CRBasic Instructions 6 3 1 1 SerialOpen All internal buffers...

Страница 27: ... None 2 7 1 This mode is only supported if there is at least a one bit delay between characters received by the SDM SIO1A TABLE 6 5 Communications Port Parameters RS 485 Full Duplex SerialOpenFormat Parity No Stop Bits No Data Bits 16 None 1 8 17 Odd 1 8 18 Even 1 8 19 None 1 8 20 Not used 21 Odd 2 8 22 Even 2 8 23 None 2 8 24 Not used 25 Odd 1 7 26 Even 1 7 271 None 1 7 28 Not used 29 Odd 2 7 30 ...

Страница 28: ...7 63 None 2 7 1 This mode is only supported if there is at least a one bit delay between characters received by the SDM SIO1A TABLE 6 7 Communications Port Parameters RS 232 Receive Only Mode SerialOpenFormat Parity No Stop Bits No Data Bits 64 None 1 8 65 Odd 1 8 66 Even 1 8 67 None 1 8 68 Not used 69 Odd 2 8 70 Even 2 8 71 None 2 8 72 Not used 73 Odd 1 7 74 Even 1 7 751 None 1 7 76 Not used 77 O...

Страница 29: ...e Where C Number of characters to transfer from the SDM SIO1A SDMRate Rate set using the SDMSpeed instruction in CRBasic giving the time in microseconds for one bit period It s worth noting that the bit rate defined by SDMSpeed is not exact and will vary slightly depending on the datalogger used If you require more accurate information about SDM data rates consult your datalogger documentation Exa...

Страница 30: ...that are currently held in its buffer 0 6143 6 3 1 8 SerialInRecord No special information 6 3 1 9 SerialFlush This instruction will purge all information in the datalogger and SDM SIO1A transmit and receive buffers 6 3 2 Example Datalogger Programs There follows two simple examples of how to write programs in CRBasic to send and receive data using the SDM SIO1A These programs are not extensive an...

Страница 31: ...ion 0 SDMSpeed 30 Optionally set the SDMSpeed not normally needed Scan 1000 mSec 0 0 Open serial port to RS 232 mode 115200bps 8 bit data 1 stop bit and no parity SerialOpen SensorPort 115200 3 100 10000 open the serial port to the sensor Request data will need to be replaced with the correct command for your sensor In this example we wait for the response Start for up to 1 second before continuin...

Страница 32: ...ould be set to position 0 SDMSpeed 30 Optionally set the SDMSpeed not normally needed Scan 1000 mSec 0 0 Open serial port to RS 485 mode 115200bps 8 bit data 1 stop bit and no parity note that the SerialOpenFormat parameter is 19 for RS 485 mode SerialOpen SensorPort 115200 19 100 10000 open the serial port to the sensor Request data will need to be replaced with the correct command for your senso...

Страница 33: ...haking is enabled but is not supported by the equipment the SDM SIO1A is connected to Once handshaking is enabled pins 8 and 11 are no longer available for general use and are dedicated to the auto handshaking system 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 call...

Страница 34: ... RS 232 signals the resting state of 6 V driving a nominal RS 232 3 k load implicitly wastes 2 mA of current per line To avoid excess current waste the chip can be turned off when not in use for example between polled measurements simply by closing the serial port using SerialClose see Section 6 3 1 2 SerialClose p 19 When running in RS 232 mode with a sensor that only sends data one way to the da...

Страница 35: ...onnected the SDM SIO1A normally operates seamlessly However there are some common issues people encounter during setup or sometimes after a period of operation During the setup phase either no data or corrupt data may be received by the datalogger When receiving data the character will be returned in place of the expected data whenever a parity framing or overrun error is detected These errors are...

Страница 36: ...ks it is transmitting and the data it is receiving by connecting to the datalogger with a computer and entering the terminal mode You can then use the W command to sniff data passing to and fro through any serial port including SDM SIO1A ports The data can be displayed in ASCII or binary HEX modes This is a powerful tool for checking programming errors and the response of remote devices See the da...

Страница 37: ... to each serial port in turn This is because each serial port has its own microprocessor with each holding their own copy of the operating system 8 2 2 Operating System Signature Errors The operating system is stored in flash memory When a new version is loaded a checksum signature is automatically created the first time its run This checksum is stored in memory This signature value can be read ba...

Страница 38: ...as four byte HEX string Public Sig_Value_Dec Holds sig as a decimal number Change this address to match the SDM SIO1A SDM address Const SDM_Address 0 Dim Src As String 1 Const cmd 5 constant cmd 0 7 Const bytes_out 1 constant number of bytes out Const bytes_val 1 constant bytes per value 1 2 4 Const big_endian 1 constant 1 big endian or 0 little endian Const delay_usec 0 constant delay between out...

Страница 39: ... input line on an SDM SIO1A Using the SDMGeneric instruction Public sio1response As Long Inputstate As Boolean Const addr 0 constant sdm address CHANGE with SDM SIO1A address Const cmd 1 constant command 1 returns the input state in bit 16 Const bytes_out 0 constant number of bytes out none sent Const bytes_val 2 two bytes returned Const big_endian 1 1 big endian Const delay_usec 0 delay between o...

Страница 40: ...setting the output pin SerialOutBlock 32 1 0 This will set the spare output pin high SerialOutBlock 32 0 0 This will set the spare output pin low The two example lines of code above will set the output pin on the SDM SIO1A high then low respectively on the SDM SIO1A device set to address 0 on its rotary switch Any value greater than 1 will set the output pin high but usually the number 1 is used a...

Страница 41: ...devices can be connected to the equivalent multifunction terminals on the SDM SIO1A The labelling for the RS 422 RS 485 functions has also been changed to avoid the confusion caused by different labelling conventions used for the A and B terminals by different manufacturers To avoid this the SDM SIO1A uses the alternative TD TD RD RD scheme of labelling with the TD and TD pair being those used for...

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