“Halo” System Communication Protocol Revision 0.
“Halo” System: Communication Protocol 970-00002-000 Revisions Version Date Changed by Description 0.
“Halo” System: Communication Protocol 970-00002-000 Approvals COO ______________________________________ Date: ___________________ Engineering ______________________________________ Date: ___________________ Manufacturing ______________________________________ Date: ___________________ Quality ______________________________________ Date: ___________________ Purchasing ______________________________________ Date: ___________________ EXI Wireless Systems, Confidential Page 3 of 33 Jul
“Halo” System: Communication Protocol 970-00002-000 1. Document Purpose .......................................................................................................... 6 2. Introduction ..................................................................................................................... 7 3. System Architecture......................................................................................................... 8 3.1. Host.....................................................
“Halo” System: Communication Protocol 970-00002-000 7.2. Network performance ..............................................................................................26 7.3. Communication parameters.....................................................................................27 7.4. Message format.........................................................................................................27 7.5. Message Structure ..............................................................
“Halo” System: Communication Protocol 970-00002-000 1. Document Purpose This document describes a communication protocol used by “HALO” system. This document is written after the system design has been finished and the objective is to describe structure of the system protocol, not only to people directly involved in the software and firmware design but to other technical personnel as well, involved in other aspects of system design, installation or technical support.
“Halo” System: Communication Protocol 970-00002-000 2. Introduction “Hallo” system is specialized data gathering and control system which is using different communication media and protocols to achieve its tasks. The system consists of several major building blocks – Host, Controllers (Elevators, Receivers) and Tags. Data that are gathered are information sent by the Tags.
“Halo” System: Communication Protocol 970-00002-000 3. System Architecture The “Hallo’ system can be classified into the group of data gathering and control systems and its components could be divided into 3 major groups: • Host (Computer) • Data gathering and control nodes (Controllers, Elevators, Receivers, Printer Interface, Programmers) • Sensors (P-Tag, A-Tag, D-Tag) Figure 1 shows how these units are organized within the system. 3.1.
“Halo” System: Communication Protocol 970-00002-000 3.2.1. Controller The Controller is used to monitor and control the area in which it is installed, usually near the door. It generates the “field of coverage” around itself and any Tag entering this field will be registered by the Controller (Tag In the Field (TIF) alarm). The other Controller’s task is to register if any of the Tags are sending TIC alarm.
“Halo” System: Communication Protocol 970-00002-000 3.4.1. RF Communication RF communication is taking place between Controllers, Elevators, Receivers on the one side an the Tags on the other. This is two-way communication accomplished on 433.92 MHz in one direction and 307 kHz in the other. 3.4.2. Weigand Communication Weigand protocol is used between Controllers, Elevators, Receivers and corresponding RIMs.
“Halo” System: Communication Protocol 970-00002-000 4. RF Communication Protocol All communication between the Tags and the Controllers is taking place across RF communication media. Two frequencies are used:433.92 MHz and 307 kHz. • 433.92 MHz Communication This is a frequency which is used to transfer information from the Tag to the Controller. The guaranteed range is 30 feet.
“Halo” System: Communication Protocol 970-00002-000 Figure 2 Wakeup Word 2 ms 500 µs 3 ms WAKEUP WORD ‘1’ ‘0’ ‘0’ ‘1’ ‘0’ ‘1’ ‘1’ ‘1’ WAKEUP RESPOND WAKEUP + RESPOND WORD ‘1’ ‘0’ ‘0’ 100 ms WAKEUP ‘1’ ‘0’ ‘1’ ‘1’ ‘1’ ‘0’ ‘0’ ‘1’ ‘1’ 100 ms WAKEUP + RESPOND WAKEUP WAKEUP + RESPOND WAKEUP WAKEUP + RESPOND 4.1.2. Bit By Bit Interrogation Upon power up the microprocessor waits for the next “wakeup word”.
“Halo” System: Communication Protocol 970-00002-000 After it transmits all 24 bits of the ID word (3 bytes are treated as one ID word) in the PWM format, the Tag sends additional byte in a NRZ (non return to zero) format. This is a checksum of the previous ID word which will be used by the Controller to ensure that the received ID number is correct. The main characteristic of the NRZ code is that bits are represented by the duration of the logic state and not by the logic state itself.
“Halo” System: Communication Protocol 970-00002-000 4.1.4. Reset Command The Reset command is issued by the Elevator when the door closes. The Elevator needs to know which Tags are inside the Elevator and in order to force them to send their ID numbers again, it resets them all. The Elevator will repeat this every time when the door opens and closes. The Tags are in the sleep mode most of the time while in the field (to preserve power).
“Halo” System: Communication Protocol 970-00002-000 4.2.1. Message format The Tag (any of the above) is powered down most of the time and it powers up only when it enters the “field of coverage” (TIF) or when it needs to generate the TIC alarm. The TIC alarm range should be much longer than a TIF alarm and this is accomplished with some tradeoffs.
“Halo” System: Communication Protocol 970-00002-000 Figure 5 TIC Alarm 850 ms a) 2 ms b) 1 ms c) ID 1 ID 2 ID 3 CHECKSUM 4.2.2. ID number format Three ID bytes carry information about 6 ID characters in the BCD format (Hexadecimal numbers 0 – F) as presented in the Figure 6a. All ID numbers are generated as sequential decimal numbers with the exception of the first character which is always the same for the particular type of Tag Figure 6.
“Halo” System: Communication Protocol 970-00002-000 5. Weigand Communication Protocol The Controller communicates to the Host PC through the “RS-485 Interface Module” (RIM). The RIM sends information to the Controller via control lines and receives information from the Controller via the Weigand lines. These two communications could take place at the same time due to multitasking nature of the Controller’s and RIM’s firmware. 5.1.
“Halo” System: Communication Protocol 970-00002-000 Table 2 Weigand Message Field Length Description Even Parity Bit Control Code Door Bit Maglock Bit Data 1 Data 2 Data 3 Odd Parity Bit 1 4 1 1 8 8 8 1 Parity Bit + next 16 bits = 0 Defines message type 1 = Door Open, 0 = Door Closed 1 = Maglock On, 0 = Maglock Off Dependant on message type Dependant on message type Dependant on message type Odd Bit + previous 16 bits = 1 Total 32 5.2.1.
“Halo” System: Communication Protocol 970-00002-000 5.2.2. Control Code This 4-bit field identifies message type. A content of three data bytes (Data 1, Data 2 and Data 3) is determined by this field. There are two groups of message types, messages which carry Tag’s ID number and all others. An overview of all message types is presented in the Table 2. No ID ID Messages Table 3 Message Type Control Code Normal Bypassed TIF Alarm Loiter Host Alarm is ON Unlock Req.
“Halo” System: Communication Protocol 970-00002-000 5.2.2.5. Host Alarm ON Message which informs the host that its command to set the alarm has been received and that the Controller is in the alarm mode. 5.2.2.6. Unlock Request ON Message which informs the Host that its command to unlock the door has been received and the door is unlocked. 5.2.2.7. TIC Alarm Message sent when TIC alarm is received from the Tag.
“Halo” System: Communication Protocol 3 4 5 6 7, 8, 9 A B C D,E,F 970-00002-000 Patient Monitoring Patient Monitoring Article Surveillance - Protection Article Surveillance – Protection Reserved (Article Surveillance–Monitoring) Authorized Entry Authorized Entry Authorized Entry No Function Continuos alarm – fixed bypass time Alarm ends on its own – fixed bypass time Alarm ends on its own – bypass extended Alarm ends on its own – bypass extended 4 second release 8 second release Released while Tag in th
“Halo” System: Communication Protocol 970-00002-000 Table 6 “High_ID” and “Low_ID” Switch Switch Setting Selected Tags High_ID > Low_ID All Tags with selected digit (switch ID Range) equal or between the two numbers are selected.
“Halo” System: Communication Protocol Bit 0 Door 970-00002-000 0 – door closed 1 – door open When in the idle mode, the Input States field equals 73 Hex. 3. Device Status This byte describes the Controller’s state. Table 8 Device Status bit State Bit 7 Not used Bit 6 RF field occupied Tag is in the field, regardless if it generates alarm or not. Bit 5 Override Host requested. Controller releases the maglock, turn off alarm relay and both LEDs and stop all interrogation.
“Halo” System: Communication Protocol 970-00002-000 6. Signal lines communication The Weigand protocol which is unidirectional is used to transfer information from the Controller to the RIM. Some information (mostly Host requests) need to be passed from the RIM to the Controller. There are 4 signal lines that are used for this purpose and the Controller monitors these lines every 12.8 ms. There are two modes of operation for the Control lines.
“Halo” System: Communication Protocol 970-00002-000 Name Min Typical Max Figure 9 Individual Lines Control Code Individual Lines OVERRIDE UNLOCK ALARM TS TD TH STROBE EXI Wireless Systems, Confidential TS 13 ms 50 ms 25 ms TD 1 ms 13 ms 40 ms TH 13 ms 25 ms 50 ms Page 25 of 33 July 27, 1999
“Halo” System: Communication Protocol 970-00002-000 7. EIA-485 Communication Information between Controller and the Host computer are exchanged across twisted pair cable driven by EIA-485 transceivers. The Controller can not communicate directly to the Host but rather through the RIM which is a network adapter for the Controller. On the Host side, the PC has an EIA-485 network card to make this link compatible. 7.1.
“Halo” System: Communication Protocol 970-00002-000 Figure 10 shows network traffic in a case of two devices on the bus with reliable communication. Maximum number of nodes to be polled is 9 per second in ideal condition (all node responses are received). “Host Request” message packet and “RIM” response packet are separated from each other 100 µs only, and not as shown in the Figure 10.
“Halo” System: Communication Protocol 970-00002-000 Lower 6 bits: message type 1 Network Address X Data 1 Checksum Logical address assigned by the Host Message contents. Number of bytes is variable, it could be 0.
“Halo” System: Communication Protocol 970-00002-000 The RIM does not respond to this message, but the Host knows if the message has been successfully received when the RIM responds next time to other messages sent to its network address. If the RIM does not respond to those messages, the Host keeps sending “Assign Network Address’ message. 7.5.2. Test Node Presence This message allows the Host to check if the particular node (RIM) is present on the bus and is it able to communicate.
“Halo” System: Communication Protocol x x x x 0 1 1 0 970-00002-000 Enter Reader mode (Controller only) Restart Pre-alarm mode (Elevator only) x x x x 0 1 1 1 Retransmit last Tag x x x x 1 0 0 0 None 7.5.5. Device Data This message is sent as a response to the “Send / Request Data” message. It follows request message within 150 µs. The length of this message is not predictable and it depends on system activity.
“Halo” System: Communication Protocol 970-00002-000 Figure 11 EVEN PARITY BIT CODE CODE DOOR DOOR EXI Wireless Systems, Confidential MAGLOCK TAG ID MAGLOCK ODD PARITY BIT TAG ID Page 31 of 33 July 27, 1999
“Halo” System: Communication Protocol 970-00002-000 8. Glossary Checksum A number that has been calculated as a function of some message. CRC Cyclic Redundancy Code" or “Cyclic Redundancy Check”. LSb Stands for “Least Significant Bit”. This is bit 0 of a given byte or a word. MSb Stands for “Most Significant Bit”. Message Sequence of bytes which carry information from one point to the other.
“Halo” System: Communication Protocol 970-00002-000 9.
