Page tree
Skip to end of metadata
Go to start of metadata


Theory Of Operation



Single RF Network Multipoint mode allows you have up to 8 WESs and 2 or more VSCs on single coordinated RF network while still maintaining Cat 3 PLd safety. Each VSC will monitor 1 or more WESs. You must configure 2 or more VSCs to monitor each WES to maintain the Performance Level and dual path redundancy required for Cat 3.

There is one RF master / Primary Coordinator VSC in the network. It polls the 8 possible WESs sequentially for their status heartbeat. The master uses all the WES status heartbeats to generate a system status heartbeat that every device in the network can hear. The slave VSCs use this system status heartbeat to monitor one or more WESs.

The system status heartbeat is a derived message that is regularly broadcast by the master VSC. It is unlikely, but possible that an error on the master could generate false information about the WESs since this is a derived message. The WESs periodically also send an encrypted message that is rebroadcasted by the master to all devices in the network. Slave VSCs use this message to verify the system status messages are correct. The slave VSCs must receive an encrypted message before enabling its outputs. This will introduce roughly one WES Encrypted Message Rate delay transitioning from Estoped to Enabled.

One or more devices in the network can be designated as Repeater or Secondary Coordinator. This device provides a secondary sync message to coordinate frequency hopping and repeats any message it receives. The secondary Coordinator can be use to fill in weak coverage spots or extend the reach of the network. This device can be placed any where it will have good line of sight to the Primary Coordinator.


Configuration Parameter Definitions


Standard Tab

TX Power Level

This is the transmit power in dbm for most radio configurations

Network ID

This is number between 1 and 4096 that should be unique for every RF network operating at your site.

Frequency Key

This number between 0 and 14 inclusive set the pysudo random hop table. Colocated RF networks should use different keys to minimise the chance of interfearance.

Radio Setting

This defines the radio type and physical slot used. This should be set to "Slot 1 Microhard 900".

Radio Mode

The only master in the network must be the Master VSC

Wired Setting

This should be set to SRCs UART or CAN J1939 depending on the hardware configuration of your VSC. WESs should use USB.

CAN Baudrate

Set the baudrate for CAN VSCs

Advanced Tab

Multi-Master

000-0000 for multi-point

Multi-Master Sync

Not enabled for multi-point

Max Packet Size

Helps define max packet size. Should be zero for Multipoint.

Min Packet Size

Helps define max packet size. Should be 2 for Multipoint.

RF Baud Rate

Defines how fast the radio transmits data. Should be "Mcirohard 900 276K".

Retransmissions

Tells the radio many times to retransmit a packet. This is an 8-bit field. The MSB (values of 128 or greater) enable the repetition of encrypted packets.

Controls Additional Feature

Enables Repeater


Radio Diagnostics

Setting this value to 1 enables radio diagnostic reading from the master radio. Should not be used on slaves.

Multipoint Tab

Multipoint Enabled

Must be set on all devices

Logical ID

This is the source address used for sending messages on the network. The least significant 3 bits must be unique for all WESs.

Master Poll Interval

  • Master: Defines how often the master transmits the system status heartbeat.
  • Slave VSC: Unused
  • Slave WES: A setting of zero enables polling based on the master heartbeat. Any value above zero enables asynchronous operation. Each WES must be assigned TDMA slots that will not cause collisions.

Controls Additional Feature

Enables polled system

WES Encryped Msg Rate

Defines how often an encrypted message is sent. It is now recomended to send only encryped messages. Any value less than the master poll interval will cause all messages to be encrypted.

WES Encryption Key

This a 32-bit hex key that is used for message encryption between slave devices that the master can not modify without invalidating.

Associated Output ID

This logical ID of the WES that a VSC's Master Enable 2 is associated

Comms Timeout

This is the amount of time that can elapse between heartbeats from the WES before Comms Timeout estop will be generated. At the bare minimum this should be the Master Polling Rate x 8 x 3. This is a worst case timeout that is only used when the WES goes out of range. The WES will generate an asynchronous heartbeat when ever the Estop or Power button button is pressed. The longer this timeout is, the more robust the system will be to RF interference.

Encrypted Comms Timeout

This a dedicated comms timeout for encrypted messages since they are sent much less frequently.

Signal Strength Lookback

Defines the look back period for the Multipoint HB Viewer and signal strength calculations.

RX Encryption Key 0-7

Defines the key to be used to decrypt messages from WES logical IDs 0-7. A key must be provide for the Associated Output ID and any devices in the Care List Mask.

Care List Mask

This defines the functionality of Master Enable 1. Each bit in this mask defines a the logical ID of the WES the VSC will monitor.

Mesh Tab

Mesh Network

This must be enabled for multipoint configurations. It will tell the device to the program the radio with the settings in the Mesh Tab. They will be saved but ignored otherwise.

Channel Access Mode

The only approved channel access mode it TDMA.

Carrier Sense Threshold

This the threshold used to determine if the channel is being used by another device. Setting it to 0 disables listen before talk / CSMA.

Aloha Repeat Interval

Defines how often a device will try to access a channel. The lower the number, the more often the device will try channel access.

Aloha Slots

Defines the number of Aloha slots in a frame.

TDMA Slot Number

This defines the 1 based index into the Aloha frame that the device will start transmitting. The end frame is defined by the amount of data the device has to send.

Routing

Enables mesh routing between nodes. Only works for Unicast messages and there are none at the moment.

Coordinator Mode

  • Primary Coordinator: Provides FHSS coordination for the mesh network. There can only be one in the network.
  • Secondary Coordinator: Provides a redundant FHSS sync messages for geographically large networks. Used LBT/CSMA to share the available sync slot with the Primary Coordinator and any other Secondary Coordinators. There can be many Secondary Coordinators in a network.
  • Backup Coordinator: Provides redundancy for the Primary Coordinator. It will take over for the Primary Coordinator if it is not heard from with in a timeout period.
  • Slave: Standard node in the network that in not part of any infrastructure.



Configuration Instructions: Polled with VSC master



TabMaster VSCSlave VSCsWESs
PowerStandard202022

Network ID

StandardAll the same and less than 4096 and not 256
Logical IDStandardGreater than 7 and unique to the networkGreater than 7 and unique to the networkUnique to each WES and 0-7 inclusive
Frequency KeyStandardBetween 0 and 14 inclusive
Radio SettingStandardSlot 1 Microhard 900
Radio ModeStandardMasterSlaveSlave
Wired SettingStandardSRCS UARTUSB Serial
CAN BaudStandard250K

TabMaster VSCSlave VSCsWESs
Multi-masterAdvanced000-0000
Multi-master SyncAdvancedDisabled
Max packet sizeAdvanced0
Min packet sizeAdvanced2
RF Baud RateAdvancedMicrohard 900 276K
Data RateAdvanced230400
RetransmissionsAdvanced0
Radio DiagnosticsAdvanced100

TabMaster VSCSlave VSCsWESs
MultipointMultipointEnabled
Master Poll IntervalMultipoint3030 (Not used / Doesn't matter)0 (Enables polling mode)
WES Encrypted Msg RateMultipointNot SetableNot Setable1500
WES Encryption KeyMultipointNot SetableNot SetableHex 32-bit Typically all set the logical ID
Ex: Logical id 7: 77777777 
Associated Output IDMultipointThe ID associated with the ME0The ID associated with the ME0Not Setable
Comms TimeoutMultipoint2500
Encrypted Comms TimeoutMultipoint1600016000Not Setable
Signal Strength LookbackMultipoint1000
Care List MaskMultipointSet cares for ME1 Not Setable
RX Encryption Key 0-7MultipointEncryption keys to decode WES messages

TabMaster VSCSlave VSCsWESs
Mesh NetworkMeshEnabled
Channel Access ModeMeshTDMA
Carrier Sense ThresholdMesh0
Aloha Repeat IntervalMesh0
Aloha SlotsMesh4
TDMA Slot NumberMesh13

3

RoutingMeshNot Enabled
Coordinator ModeMeshPrimary CoordinatorSlave

Configuration Instructions: Asynchronous with WES master and Repeater



TabMaster WESSlave VSCsWESs
PowerStandard23

Network ID

StandardAll the same and less than 4096 and not 256
Logical IDStandardUnique to each WES and 0-7 inclusiveGreater than 7 and unique to the networkUnique to each WES and 0-7 inclusive
Frequency KeyStandardAll the same and between 0 and 14 inclusive
Radio SettingStandardSlot 1 Microhard 900
Radio ModeStandardMasterSlaveSlave
Wired SettingStandardSRCS CAN J1939SRCS CAN J1939USB Serial
CAN BaudStandard250K

TabMaster WESSlave VSCsWESs
Multi-masterAdvanced000-0000
Multi-master SyncAdvancedDisabled
Max packet sizeAdvanced0
Min packet sizeAdvanced2
RF Baud RateAdvancedMicrohard 900 276K
Data RateAdvanced230400
RetransmissionsAdvanced0 for all except Repeater VSC
128 for Repeater VSC 
Radio DiagnosticsAdvanced0

TabMaster WESSlave VSCsWESs
MultipointMultipointEnabled
Master Poll IntervalMultipoint120
WES Encrypted Msg RateMultipoint100Not Setable100
WES Encryption KeyMultipointHex 32-bit Typically all set the logical ID
Ex: Logical id 7: 77777777 
Not SetableHex 32-bit Typically all set the logical ID
Ex: Logical id 7: 77777777 
Associated Output IDMultipointNot SetableThe ID associated with the ME0Not Setable
Comms TimeoutMultipoint2500
Encrypted Comms TimeoutMultipoint25002500Not Setable
Signal Strength LookbackMultipoint1000
Care ListMultipointNot SetableSet cares for ME1 Not Setable
RX Encryption Key 0-7MultipointNot SetableEncryption keys to decode WES messagesNot Setable

TabMaster WESSlave VSCsWESs
Mesh NetworkMeshEnabled
Channel Access ModeMeshTDMA
Carrier Sense ThresholdMesh0
Aloha Repeat IntervalMesh0
Aloha SlotsMesh19
TDMA Slot NumberMesh1 + Logical ID x 217

1 + Logical ID x 2

RoutingMeshNot Enabled
Coordinator ModeMeshPrimary CoordinatorSlave

Example Care Configurations And Outputs


For each VSC, the MCU Master Enable will be de-asserted when its associated WES (set by the assoc. output ID field) is e-stopped or goes out of range. The CPLD Master Enable will be deasserted when any WES in its care list is e-stopped or goes out of range.

Single Estop or Off

WES 0 EstoppedVSC 0VSC 1VSC 2VSC 3
ME 2 - Associated1000
ME 1 - Care Group0001
WES 1 EstoppedVSC 0VSC 1VSC 2VSC 3
ME 2 - Associated0100
ME 1 - Care Group1000
WES 3 EstoppedVSC 0VSC 1VSC 2VSC 3
ME 2 - Associated0001
ME 1 - Care Group0010

Double Estop or Off

WES 1 + 3 EstoppedVSC 0VSC 1VSC 2VSC 3
ME 2 - Associated0101
ME 1 - Care Group1010
WES 2 + 3 EstoppedVSC 0VSC 1VSC 2VSC 3
ME 2 - Associated0011
ME 1 - Care Group0110


Example Config: VSC 0 through 3