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Product Overview

The Scanning Devices SD900 Bluetooth Industrial Server enables wireless access and control of industrial field signals from a suitably equipped mobile handheld computer. The SD900 Industrial Server System is designed to be installed with industrial control equipment: programmable logic controllers (PLC's), computers, sensors, actuators or instrumentation. It provides a means for wireless communications with these devices, including them in personal area networks. Communications with Scanning Devices Bluetooth Industrial Server requires a Bluetooth-equipped mobile* host such as a handheld PDA or laptop computer. The mobile host must be capable of establishing an ad hoc Bluetooth network through bluetooth discovery and connection operations, generating and transmitting commands, receiving responses and processing them as in a user-application. The mobile host communicates with Scanning Devices Bluetooth Server at the L2CAP (Logical Link Control and Adaptation Protocol) level. The mobile host generates and transmits L2CAP data packets with commands and data. The Bluetooth Server receives, interprets and processes the commands and data, then generates an L2CAP data packet in response.

SD900 Bluetooth Industrial Server System

Scanning Devices provides sample Palm OS and Pocket PC 2003 applications to demonstrate the functions of the Industrial Server from a simple Palm or Pocket PC User interface. It allows a handheld user to connect the SD900 system in a Bluetooth piconet and then access a set of discrete inputs, control a set of discrete outputs, send and receive RS232 data, all from taps on the handheld screen.

The sample application can be a starting point for custom application development. While the sample is based on Palm OS or Pocket PC 2003, any Bluetooth equipped computer capable of establishing a piconet, generating, sending and receiving commands can make use of the SD900.

This users guide describes:

• The mechanical package, mounting and wiring of the SD900
• Electrical connection of field signals
• Bluetooth communications requirements
• The Sample Application
• Development of the Sample Application
• Extensions to custom applications

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Mechanical Installation

Enclosure

Scanning Devices SD900 enclosure consists of a black polycarbonate housing shell with tan cover and 2 rows of integral terminals on 5 mm spacing. Terminals are nickle-plated brass. Enclosure dimensions are 70 x 70 x 120 (mm; L, W, D).

The SD900 mounts on a standard 35 x 7.5 mm DIN rail. It will also fit on a 35 x 15 mm DIN rail. The SD900 can also be panel mounted using pull-out tabs on the base of the enclosure. When planning for mounting, bluetooth radio reception should be considered.

The enclosure has an IP20 rating (finger protection) and meets VBG4 accident prevention requirments.

DIN Rail Mounting Procedure

The top of the enclosure base has notches molded onto the sides. The bottom of the base has one spring-loaded tab that is factory installed into a molded guide for DIN rail mounting.

When mounting, tilt the bottom of the enclosure slightly away from the rail until the notches grab onto the top flange of the DIN rail. Push the bottom of the enclosure forward towards the DIN rail. The spring-loaded tab will snap onto the bottom of the rail and hold the enclosure firmly in place.

To remove the enclosure from the DIN rail, insert a screwdriver into the exposed slot in the tab and pull the tab down. Pull enclosure forward and remove from the rail.

Terminals

Terminals are cage clamp style. Terminals accept wire up to 2.5 mm 2 (12 AWG). When the terminal screw is tightened, the serated bottom of the cage presses the wire to be terminated against the serated underside of the busbar. The busbar extends internally to a circuit board connection. Terminal screws can be operated with either a flat tip or #1 or #2 philips screwdriver.

Enclosure information is provided by Altech Corporation. More information on the SD900 Enclosure or Terminal Connection can be found at the Altech website: www.altech.com/

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Electrical Connection

The SD900 Bluetooth Server is an industrial computing system consisting of these components:

• An embedded microprocessor with fixed program memory
• Small, non-volatile user accessible memory
• UART for RS232 communications
• Discrete low-power logic inputs
• Discrete low-power current sinking outputs
• Bluetooth radio module

The computing element operates with Scanning Devices developed software to read discrete inputs, set discrete outputs ON or OFF, send and receive RS232 communications, read and write non-volatile memory, and communicate using the Bluetooth radio module. Communications uses techniques defined by the Bluetooth Specification and application commands suited to the system.

A. Discrete inputs are designed to operate with current-sinking sensors or industrial controls capable of sinking current to signal ground. Inputs are schmit trigger logic gates with inputs pulled up to 5 volts via 10 K ohm resistors. Switching occurs in a range of 1.5 - 3.5 volts. Inputs are protected from overvolt by small signal diodes. Input voltage greater than 30 volts may damage input gates.
Discrete inputs are not filtered or optically isolated. Response time from receipt of a command to read is typically measured in units of microseconds. SD900 has 8 discrete inputs organized as a group and one additional discrete signalling input. While electrically identical to the other 8, this input, termed the "Busy Input", may be read with a separate command and used to signify that the field process may be in a state where it should not be altered. The interpretation of this input is left to the client's application program.
B. Discrete ouputs are uncommitted NPN transistor collectors, designed to switch low-power dc loads, conducting up to 50 milliamps to signal ground (externally sourced) when ON and sustaining up to 30 volts when OFF. Discrete outputs are not filtered or optically isolated. Response time from receipt of a command to write is typically measured in units of microseconds.

C. RS232 interface consists of TxD and RxD signals. RTS, CTS and other flow control options are not available. Communications parameters baud rate, data bits, stop bits and parity can be set under command from the moble host. Output data is transmitted as received from the mobile host. Input data is held in an input buffer, up to 128 bytes, until read by the mobile host. As currently implemented, data characters received when the input buffer is full are lost.

D. Up to 64 bytes of local non-volatile memory is available for temporary data storage in the server. Data is read and written by commands from the mobile host.

Power Requirements

Power requirements are:
Input voltage: 10-30 volts DC
Current required (exclusive of attached field devices): 125 milliamps

SD900 Wiring Diagram

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Bluetooth Wireless Communications

SD900 Server operates as a slave device in a Bluetooth piconet. It responds to inquiries, connection requests and commands issued by the mobile client and piconet master. SD900 does not initiate any Bluetooth communications, only responding to communications received.

On Power Up

On power up, SD900 reads non-volatile memory and sets its discrete outputs and RS232 communications parameters with the settings saved previously. One set of commands stores these settings so that the host need not be involved at power up time. The bluetooth radio is enabled and the SD900 is ready to communicate.

Once connected to a client, SD900 responds to commands generated and transmitted to it by the client. SD900 interprets the command, performs the commanded operation, and transmits a response to the host. The response may be an acknowledgement that the command was executed or may include data, depending on the command. Commands are processed as single thread. SD900 processes each command to completion before responding to another command.

Each command is represented by a single ASCII character. The following table presents the command character, the pneumonic representation, action, the response characer and pneumonic and any data transmitted with the response.

Commands, Actions and Responses

These commands enable a mobile handheld user to interact with field signals over a wireless link from an application on the handheld. Multiple consecutive commands can be issued by the application to perform more complex sequences. The ASCII character used to represent the command is shown in bold.

Client Command pneumonic	Command Data	SD900 Action	SD900 Response pneumonic	Response Data
A GET_BUSY _STATE	None	Read Input	B GET_BUSY_ STATE_ RESPONSE	Status 0 or 1
C GET_COMM_ SETTINGS	None	Read Comm Settings	D GET_COMM_ SETTINGS_ RESPONSE	Baud Rate, Data bits, Parity, Stop bits
E GET_DISCRETE_ INPUTS	None	Read Discrete Inputs	F GET_DISCRETE_ INPUTS_ RESPONSE	Byte with 8 input states
G GET_INITIAL_ DISCRETE_ OUTPUTS	None	Read initial output setttings from non-volatile memory	H GET_INITIAL_ DISCRETE_ OUTPUTS_ RESPONSE	Byte with 8 initial output states
I GET_RECEIVE_ DATA	None	Read data in com port input buffer (placed on receipt from external RS232 device)	J GET_RECEIVE_ DATA_ RESPONSE	Data from com port input buffer
K SET_COMM_ SETTINGS	Baud Rate, databits, parity, stop bits	Setup the com port with these parameters 0	L SET_COMM_ SETTINGS_ RESPONSE	None
M SET_ DISCRETE_ OUTPUTS	Byte with 8 output states	Set the outputs	N SET_ DISCRETE_ OUTPUTS_ RESPONSE	None
O SET_ INITIAL_ DISCRETE_ OUTPUTS	Byte with 8 initial output states	Save the byte in non-volatile memory	P SET_ INITIAL_ DISCRETE_OUTPUTS_ RESPONSE	None
Q SET_ LOCAL_NAME	String with new local name.	Set the Local Name.	R SET_ LOCAL_ NAME_ RESPONSE	None
S SET_ TRANSMIT_ DATA	Data to send from com port	Write data to comm output buffer, initiate transmission	T SET_ TRANSMIT_ DATA_ RESPONSE	None
U GET_ SAVED_ DATA	None	Reads application data from non-volatile memory.	V GET_ SAVED_DATA_ RESPONSE	Saved Data
W SET_ SAVED_ DATA	Data to save in non-volatile memory	Saves application data	X SET_ SAVED_ DATA_ RESPONSE	None

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The Users Guide continues in Part 2