Sierra Radio Systems. DCN Device Control Network. Reference Manual. Version 1.0

Transcription

1 Sierra Radio Systems DCN Device Control Network Reference Manual Version 1.0

2 Sierra Radio Systems Device Control Network DCN INTRODUCTION The Sierra Radio Systems Device Control Network (DCN) provides a way to allow multiple devices communicate on a wired or wireless network. The primary application for the DCN is to allow a master computer or device, to control and monitor a network of real-time control devices. The DCN specification defines four components, the physical and RF connections and electrical signals, data link layer, the application layer and network topology. The purpose of the physical layer is to define the standard mechanical connectors, pin assignments, signaling voltages, and RF frequencies. The next layer up, the data link layer, defines the format of data packets sent on the network. The third layer defines the format of the payload being sent from point A to point B and finally recommendations for the network topology. SECTION 1 - PHYSICAL CONNECTIONS AND ELECTRICAL SIGNALING The DCN is a dual-band system meaning that data may be transmitted over wired or RF communications paths or both. Physical Connections The control protocol can be transmitted over any type of communications medium. The most common connections are wired through an RS232 or RS485 connection, a wireless connection, typically using an RF mesh data network or over ethernet. Wired RS-485 The RS485 wired implementation uses commonly available Ethernet CAT5 cable and RJ-45 connectors. While the DCN protocol has nothing at all to do with Ethernet except that we take advantage of the wide availability of premade cables. The CAT5 cable provides 8 wires which carry the network traffic and power. Many devices have two RJ-45 connectors wired in parallel. This allows for easy daisy-chaining of multiple devices using CAT5 cable. This makes it easy to add more devices to the network without the need for any kind of hub or switch. RJ-45 Cable Assignments 1 Network data signal A 5 - Ground 2 Network data signal B 6 - Reserved 3 Reserved VDC 4 Ground VDC

3 Wired RS-485 Electrical Signaling - continued The electrical signaling used is based on RS-485. This signaling technique is a half-duplex, differential pair that allows multiple devices to be connected to a single pair of wires. RS-485 also has the advantage of allowing devices to be spread over 1000 s of feet of cable without the need for signal conditioning or repeaters. Power can be supplied by any device and delivered to all devices on the network. If a device can supply power to the network, there must be a way to disconnect the power, usually through a jumper block. Only 1 device is allowed to supply power to the network at a time. Network voltage should be between VDC. This provides enough of headroom to power any DCN compatible device. Wireless RF Data Network The DCN can also use RF modules that operate on 2.4 GHz and 900 MHz. If mesh network radio modules are used, if you add new nodes to the RF network, the automatically become part of the network. This is particularly convenient when extending the range between devices. Each node can be thought of as a serial port that taps into an invisible network of other devices. When data is sent into the serial port of the data radio, the packet will be delivered to every data radio in the network and the packet will be transmitted out of the RF module s serial port into the local device s CPU. A network can consist of a mixture of wired RS-485 and RF data network enabled nodes.

4 SECTION 2 - DATA RATES AND PACKET FORMAT The DCN data protocol sends ASCII data at 9600 baud, non-inverted, 8 bits, no parity. The protocol defines the format of packets of data transmitted on the network. The simple way to think of a packet is a string of ASCII characters that contains the payload to be transmitted from point A to point B and the additional characters necessary to provide synchronization, packet type identification, addressing, and error checking. A typical packet looks like this... /A01:RY1,1:4D <13> Start Packet From To : Payload : LRC End of Type Address Address Value of Packet Packet Start of Packet A forward slash character / is reserved for the start of packet indication. When a slave device sees the slash, it knows there is a new packet. Packet Type The packet type character defines the format of the packet and instructions for how the packet is to be interpreted. Packet types include direct, addressed and addressed with no error checking. They start each packet with the characters //, /A, and /0 (zero) respectively. Direct Packet type // ( Example: //reset ) This is a very simple format that is intended only for use in a system with a single node. The format for a direct packet is simply the header // and the payload. As you can see, there is no address or error checking. If multiple nodes are on the network and a direct command is issued, all nodes will decode and execute the command. This can be very convenient to send master commands to all nodes but there is no error checking. Addressed Packet type /A ( Example: /A01:reset:39 ) These packets start with /A and contain the source and destination address, payload and error check data. Addressed Packet, no error checking type /0 ( Example: /001:reset:34 ) This is an Addressed packet that ignores the error checking field. This is used for manual entry of network addressed packets without the need to calculate the error checking value.

5 Device Addresses You can assign any node an address using any printable character. However, for maximum functionality, we recommend using numbers as the addresses.. Pre-assigned default device addresses 0 System master Devices Station Controller 2 Remote RF coax relay 3 GPIO board 4 Not assigned 5 Not assigned 6 Not assigned 7 RadioRouter audio mixing and switching device 8 Not assigned 9 Not assigned A-Z Not assigned * Broadcast to all devices. Any other characters are reserved and should not be used. If you add a second device and the default device address is already in use, just pick another. Payload The payload is application dependent. See standard command summary. Error Check Value The error check value is an 8 bit LRC.. The LRC is applied to all characters in the packet except the initial start of packet character /. Of course the LRC is not applied to the LRC characters either. Example: with the packet /A01:reset:39 the LRC is applied to A01:reset: End of Packet The end of packet character is a carriage return, ASCII byte value 013 (decimal). When an end of packet character is encountered, the input buffer is evaluated. The evaluation process identifies a packet by finding the start of packet synchronizing character / and extracts the buffer contents up to the end of packet character. The command parser then extracts the packet type, addresses, error check value and payload. The error check value is calculated and compared to the packets error check value. If the values do not match, the buffer is flushed. If the packet is good, then the to address is examined. If the to address is the same value as the devices address, the packet analysis will continue, if not, the packet is ignored and flushed from the buffer.

6 PAYLOAD FORMAT The payload may contain any printable characters (0-9, A-Z, a-z, and punctuation except / and,) The payload may contain from zero to 9 fields delimited by commas. The comma delimiter must be placed between fields and not at the beginning of the payload. The payload field assignment is typically a command field followed by zero to 8 argument fields. For example: RY1,0 Where the command is RY1 and argument 1 is 0. In this example the command tells the target device to set relay 1 to a value of 0 (or off).

7 STANDARD COMMANDS Every device may support a different set of commands. Refer to the device s reference manual for specific commands supported. These examples are presented to provide examples of typical commands. Common System Commands PING,2 Pings device #2 ROLLCALL Every device will respond with its registration state (registered or not) REBOOT Restart the device REGISTER Tell the device the master knows it is there RELEASE Tell the device it is no longer registered to the master SETADDR,5 Set device address to 5. Dip switch over rides this on reboot ECHO,BLA Send the string BLA back to the master HELP Display help information System Controller specific commands Relay commands RY,10100 Set relays 1..5 to be on, off, on, off, off RY3,1 Set relay 3 to be on (options: 1=on, 0=off, T=Toggle, P=Pulse) Front panel commands FP,BEEP,2 Generate 2 beeps FP,CW,CQDX Send CQDX in CW FP,VOL,50 Set the tone generator to a volume of 50 in a range from 0 to 255 FP,LCD,2,5,HELLO Tell the front panel processor to display the string HELLO on line 2 character position 5 FP,LCD,CLS Clear LCD screen

8 Xbee Firmware Configuration Guide Introduction The xbee line of data radio modules from Digi-International are very flexible and can be configured in a variety of ways. These devices support two different network protocols ZigBee and Digi-Mesh. Both protocol stacks are built on the industry standard IEEE network layers. ZigBee and Digi-Mesh build functionality on top of that. Each protocol offers many configuration parameters to tailor the device s behavior to meet the needs of a wide range of applications. For a complete description of configuration options refer to the Digi web site for more details. It is far beyond the scope of this document to present all protocol, and configuration options. We have selected a specific configuration that works very well for the vast majority of applications. If you need different functionality, consult the Digi web site and on-line support groups. To install firmware and set configuration parameters in each radio module, you will use a program called X-CTU available free from Digi-International. Firmware Stack We recommend the Digi-Mesh protocol stack for our HamStack projects. Digi-Mesh has most of the advantages of the ZigBee mesh network protocol but is simpler to configure and deploy. The only disadvantage to Digi-Mesh is that many vendors support ZigBee while Digi-Mesh is unique to Digi- International products. One great feature of the Digi products is the ability to re-flash the firmware in each module with different protocols. If you start with Digi-Mesh and want to experiment with ZibBee, you just need to load the ZigBee firmware and you are ready to go. Step 1 Install X-CTU PC software The X-CTU software can be downloaded from the Digi-International web site. Step 2 - Install the Digi-Mesh firmware For the 2.4 GHz xbee (1mw) module, install modem firmware type: XB24-DM For the 2.4 GHz xbee PRO module, install modem firmware type: XBP24-DM For the 900 MHz xbee PRO module, install modem firmware type: XPB09-DM The field Function Set should be set to XBEE PRO DIGIMESH 2.4 There are only a few configuration parameters required to get your data radio module up and running on the network. Step 3 - Set network ID This is the name of the RF network that all units will join. This is an arbitrary 4 digit number. You can pick any number you want. You can run multiple independent networks on the same RF channel by setting some modules to one address and other modules in another network to another address and they will ignore each other. HamStack default recommendation: Set Networking ID Modem VID to 7373

9 xbee Firmware Configuration Guide Step 4 Set operating channel This is one of the 12 available RF carrier channels that the network will operate on. Channels are assigned values from 0C to 17 (C, D, E, F, 10, 11, 12,13,14,15, 16, 17, 18) represented as a hex value. The RF carrier channels overlap with other devices in the 2.4 GHz band including WiFi and Bluetooth networks. Generally speaking you can pick any channel and it will work fine even with these other networks in operation. If you are in an RF dense environment and want to take all steps possible to avoid interference, pick a channel that does not overlap with your local WiFi networks. See the frequency table in the appendix. We recommend using channel C, this channel overlaps with WiFi channels 1, 2 and 3. HamStack default recommendation: Set Network CH Operating Channel to C Step 5 Set device address Setting the high order destination address to 0 and the low order destination address to FFFF will put the radio in broadcast mode. All data packets received will be sent to the serial port. In a HamStack environment running the StationStack Network Control Protocol on the HamStack CPU, the device address decoding is done by the HamStack CPU. This makes the network operate as a simple mesh of all devices where any data going into one data radio s serial port will appear at the output of all data radios. The HamStack CPU will then process the payload of the packets. HamStack default recommendation: Set Addressing DL Destination Address Low to FFFF Set Addressing DH Destination Address High to 0 Step 6 Set serial port configuration The data radio module s serial port can be configured to one of eight standard baud rates including 1200, 2400, 4800, 9600, 19200, 38400, 57600, , and baud. HamStack default recommendation: Set Serial Interfacing BD Baud Rate to 9600

10 Digi International X-CTU firmware configuration software

11 Network Topology Overview The Sierra Radio Device Control Network can be build with wired or wireless devices or a combination of both. The network protocol is completely independent from the physical communications channels. In the DCN, all devices are listening all the time to the network. One device, typically a computer, is the master and all other devices are slaves. All slaves remain quiet until the master communicates with them. Every device, including the master has unique address. Typically the master is address 0 (zero) and devices are numbered 1, 2, 3 and so on. Think of the network as one big party line where everyone is connected all the time. When anyone transmits, all devices can hear it. There are three commonly used physical connections used in a DCN. They are RS232 for point to point applications with one master and one slave device. RS485 which is a serial interface but very different from RS232. RS485 uses differential signaling on a pair of wires (called the A and B wires) and operate half duplex. The advantage to RS485 is the ability to hang multiple devices on the A/B pair and the long physical distances that can be used. The third common connection type is an RF data channel. The DCN data radios take serial data into their UART and package the data up in a packet and transmits them to the other data radios in the network where the same data comes out the UART on the other end and into the local devices microcontroller. Lets look at some typical network configurations. RS232 or RS485 Master Address: 0 Device Address: 1 In the most simple example, the master can talk to a slave over a wired connection. Some Sierra Radio products have RS232 ports but all devices have the RS485 DCN connector which is a RJ45 (ethernet) modular connector. 2.4 GHz RF Path Data Radio Master Address: 0 Data Radio Device Address: 1 When using a RF data radio module instead of a wired connection, the logical behavior is exactly the same. Data that comes out of the master s UART will arrive at the input to the UART on the slave.

12 RS485 over CAT5 RS485 over CAT5 RS232 Network Topology Wired and wireless connections can be combined. One example is where the local devices are connected with cable and the remote devices connected with a wireless data connection. For example Master Address: GHz RF Path Data Radio RS232 RS485 Communication Bridge Device Address: 1 Device Address: 2 Data Radio RS232 RS485 Communication Bridge Device Address: 3 Device Address: 4 In this example, all devices are listing at the same time to the DCN regardless of the medium of communications.

13 DigiMesh RF Data Module Reference

14 Appendix Standard Commands Used By All Devices

15 STANDARD COMMANDS ALL DEVICES Every device may support a different set of commands. Refer to the device s reference manual for specific commands supported. These examples are presented to provide examples of typical commands. Common System Commands PING,2 Pings device #2 ROLLCALL Every device will respond with its registration state (registered or not) REBOOT Restart the device REGISTER Tell the device the master knows it is there RELEASE Tell the device it is no longer registered to the master SETADDR,5 Set device address to 5. Dip switch over rides this on reboot ECHO,BLA Send the string BLA back to the master HELP Display help information System Controller specific commands Relay commands RY,10100 Set relays 1..5 to be on, off, on, off, off RY3,1 Set relay 3 to be on (options: 1=on, 0=off, T=Toggle, P=Pulse) Front panel commands FP,BEEP,2 Generate 2 beeps FP,CW,CQDX Send CQDX in CW FP,VOL,50 Set the tone generator to a volume of 50 in a range from 0 to 255 FP,LCD,2,5,HELLO Tell the front panel processor to display the string HELLO on line 2 character position 5 FP,LCD,CLS Clear LCD screen

16 STANDARD COMMANDS ALL DEVICES Administrative Commands Command Example Definition SETADDR,<string> //SETADDR,5 Sets the network address for the RadioRouter to <string>, where <string> is a single, printable ASCII character. The default address for the RadioRouter is 9 While the address character can be any single character we recommend the following guidelines for address programming. 0 Reserved for the controlling PC 1 Reserved for a hardware control head 2 9 Recommended for all user devices A Z Also available for user devices * Reserved for broadcast All others Punctuation is reserved for system use. Avoid lower case letters to prevent confusion and accidental upper case translation. Command Example Definition REBOOT //REBOOT This is a soft reboot command will re-start the RadioRouter. Command Example Definition PING //PING This will return the name, address and type of connected device. Command Example Definition ROLLCALL //ROLLCALL This will return the name, address and type of connected device from all devices on the network. Each device will wait for a short period of timebefore sending its response. The delay time is calculated based on the device address. For example an address of 5 will wait 5 * 100 ms = 500 ms. This will minimize or avoid collisions. Command Example Definition STATUS //STATUS This will return useful status information about the connected device.

17 Appendix Device Specific Commands

18 DEVICE SPECIFIC COMMANDS - Station Controller Get Station Controller Status Command STATE Example //STATE Will return the state of the station controller Return payload format UPDATE,1,SC1,RY,DI,Vin,Vout,current,Fwd,Rev,Max,Sense,RefVoltage,AN1,AN2,temp 1 Device address 1 SC1 Device type SC1 (Station Controller 1) RY Relay state (Relay 1 Relay 5) DI Digital inputs 1 and 2 Vin DC power relay voltage input Vout DC power relay voltage output Current DC current flowing through the DC power relay Fwd Forward RF power Rev Reflected RF power Max Max voltage from directional coupler Sense Directional coupler sense voltage RefV Reference voltage to be calibrated out of the RF power measurements AN1,2 User analog voltage input 0-30VDC each Temp Temperature in degrees F from the digital temperature probe Example UPDATE,1,SC1,11111,00,13.8,13.7,14,55,0,2.5,2.0,0.14,13.8,6.0,68 Turn on / off Relays Command RYx,y Example //RY1,1 Will turn relays on or off where x is the relay number 1 5 and y is the state (1=on, 0=off) Relay number (x) Relay 1 DC power control Relay 2 AC power control Relay 3 User relay 1 Relay 4 User relay 2 Relay 5 User relay 3 Relay state (y) 1 or on Relay on 0 or off Relay off P Pulse relay for 250 ms. T Toggle state

19 DEVICE SPECIFIC COMMANDS - RadioRouter RX mixer channel control Command MIX,<mask> Example //MIX,10X00000 Will turn on port 1, and turn off ports 2,4,5,6,7,8 Regardless of the current state port 3 will be unchanged Argument definition <mask> is a string of 8 characters that turn each mixer channel 1 8 on or off. 1 = port on 0 = port off X = do not change the current state of the channel Master receiver audio mixer volume Command VOL, <value> Example //VOL,100 Argument definition <value> is a number between 0 and 255 which will set the master volume. 0 = off and 255 is maximum volume. The default is typically 100 which is close to mid scale. Individual channel volume is set with the radio s volume control. Transmitter selection Command TXn (TX1, TX2, TX3, TX4) Example //TX1 Argument definition: none. Sets the focus of the transmitter board to transmitter 1 or 2 when using one transmitter board or between 1, 2, 3, or 4 when using two transmitter boards. Speaker control Command SPEAKER,<value> Example //SPEAKER,ON Definition Enable / disable speaker output. <value> can be one of the following strings ON or 1 = speaker enabled OFF or 0 = speaker disabled

20 DEVICE SPECIFIC COMMANDS - RadioRouter Operating Mode Selection Command MODE,<value> Example //MODE,1 Sets operating mode of the RadioRouter. Argument definition <value> is one of the following options 1 = Mode 1. Control head or PC virtual control head control (default) 2 = Mode 2. OTRSP SO2R compatible mode. Notes on Mode Usage Mode 1 StationStack Control Head or Control Head Software This is typically used with a PC virtual control head program or a hardware control head using the StationStack Control Protocol where the packets are either fully addressed (/A) type or direct (//) type. For example a direct command to turn on Rx port 1 would be //MIX,1XXXXXXX Mode 2 OTRSP Logging Computer Program This is used when the RadioRouter is being controlled from a contesting program such as WinTest or WriteLog using the Open Two Radio Switching Protocol (OTRSP). This format does not use any packet framing characters, like /A01:. The OTRSP commands are sent in raw form. A command payload of TX1 to select transmitter 1 is simply sent as TX1 from the logging program. Setting the Mode Manually with the Reset and Mode buttons The mode can also be set at boot time with the Reset and Mode buttons found on the CPU or Tx boards. When the RadioRouter powers up, it will flash the Status LED a few times indicating that power has been applied and it is going through its boot process. After about 5 seconds, the RadioRouter is booted and ready to be used. At this point the Status LED goes to a solid green indicating the normal on condition. To set the mode manually with these buttons, hold the Mode button down, then press the Reset button briefly, still holding the Mode button. After the Status LED initially flashes, a few seconds later the Status LED will then blink once. If you want to boot in mode 1, you have two seconds to let go of the Mode button at that point. If you want to boot in mode 2, continue holding down the Mode button. After the Status LED blinks twice, let go of the mode button. In a few seconds, the Status LED will send either the number 1 ( ) or the number two ( ) in CW indicating which mode was selected. Timing is critical. If you bounce you finger on one of the buttons or hold it down too long, you may set the wrong mode. Repeat the process to set it to the mode you want. Every time the mode is set, it will be stored in flash memory and when the device is re-booted, it will come up in the mode that was last set.

21 DEVICE SPECIFIC COMMANDS - RadioRouter Headphone output control Command PHONES,<value> Example //PHONES,ON Definition Enable / disable headphone output. <value> can be one of the following strings ON or 1 = headphones enabled OFF or 0 = headphones disabled OTRSP Compatible Commands This is an open standard protocol used to control hardware devices in an SO2R contest station. OTRSP is the Open Two Radio Switching Protocol. The RadioRouter supports the most common basic OTRSP commands that are used on popular logging programs including WinTest, W1MM and WriteLog. Supported OTRSP commands RX1 Listen to radio 1 RX1S Listen to radio 1 RX2 Listen to radio 2 RX2S Listen to radio 2 RX1R Listen to both 1 & 2 RX2R Listen to both 1 & 2?RX Returns the mode set TX1 Set tx focus to radio 1 TX2 Set tx focus to radio 2?TX Returns radio with focus?name Sets the name of the device to TEXT (up to 32 chars)?fw Returns the firmware version Command Example Definition PHONES,<value> //PHONES,ON Enable / disable headphone output. <value> can be one of the following strings ON or 1 = headphones enabled OFF or 0 = headphones disabled

22 DEVICE SPECIFIC COMMANDS - Control Head Control Head Commands These are commands that the master controlling device will respond to. The control head can be a physical control head or a virtual control head implemented in software on a PC. In either case, they should behave the same way. Command Example Definition LCD,<row>,<column>,<string> //LCD,2,5,W1AW The RadioRouter assumes an LCD of at least 2 rows and 20 columns. This command displays the text string W1AW <string> on row 2 starting at character position 5. The LCD command also responds to a special command CLS in the format //LCD,CLS The CLS argument will clear the LCD display screen Command Example Definition LED,<led_mask> //LED, 1100XXGGRRYY This command will set the state of the control head LEDs. The RadioRouter assumes 12 LED are available. The <led_mask> is a 12 character string that represents the state of each LED from #1 to #12. Each character can be one of the following values. Character Meaning What is displayed 1 On Green 0 <zero> Off Off G On Green O <letter O> Off Off R Red Not used Y Yellow Not used X No change What ever the previous state was Examples LED, Turn on LEDs 1-4 and 9-12, turn off 5-8 LED,GGGRRRYYYOOO Set LED 1-3 Green, 4-6 Red, 7-9 Yellow, off LED,XXXXGXXXXXXX Set LED 5 on, don t touch the others. Note, trailing X s can be left off and the control head will assume they are X. Example LED,XX1 is the same as LED,XX1XXXXXXXXX

23 GPIO-2 STATION CONTROLLER SUPPORTED COMMANDS Relay control Command RY,<mask> Example //RY,10X00000 Will turn on relay 1, and turn off relays 2,4,5,6,7,8 Regardless of the current state relay 3 will be unchanged Argument definition <mask> is a string of 8 characters that turn each realy 1 8 on or off. 1 = relay on 0 = relay off X = do not change the current state of the relay Individual realy Command RYn,<state> Example //RY3,1 Argument definition Where n is a value of 1..8 mapped to relays 1..8 <state> is one of the values 0, 1, T, P. 0 = relay off 1 = relay on T = toggle state (flip on to off and off to on) P = pulse. Assuming the relay is normally off, the relay is set off then pulsed on for 250 ms. then set to the off state. Get the state of the GPIO board Command STATE Example //STATE Argument definition: none. Returns the current state of the GPIO board in the format: //STATE, ,0000,13.8,13.8,13.8,13.8 In this example represents the state of the relays #1.. # represents the state of the digital inputs #1.. #4 13.8, 13.8, 13.8, 13.8 represents the values of the A to D inputs #1.. #4 State will also send the following additional commands to the master control unit or program: //LED, See //LED command for details //LCD,1,1,TEXT See //LCD command for details //LCD,2,1,TEXT See //LCD command for details //TAGLINE,TEXT See //TAGLINE command for details

24 GPIO-2 STATION CONTROLLER SUPPORTED COMMANDS LED command This command is send from the GPIO board back to the master controlling device. The master can be a PC program, iphone, or hardware control head. This command updates the state of the LEDs on the master control panel or control head. Command LED,<mask> Example //LED,10GYYRX00000 The mask maps to LED s #1.. #12 <mask> is a string of 12 characters that turn each LED on and off 1 or G = Turn LED on with a green color 0 (zero) = Turn LED off R = Turn LED on with a red color Y = Turn LED on with a yellow color X = do not change the current state of the LED LCD command This command sends a text string to the master control program or control head to set characters to be displayed on the LCD screen. Command LCD,line,col,text Example //LCD,1,5,Hello Argument definition line is the line 1 or 2 where the text will appear col is the column where the text will start typically between 1 and 16 text is the text string that will be written on line starting in column col Trailing spaces are truncated. Any text written past the end of the display are lost Tagline Command TAGLINE Example //TAGLINE,W1AW Tagline places the text string on the control panel s tagline usually near the top of the display. This is provided for users to annotate a title to the control panel to personalize the display. Typically used for callsigns, names, or the purpose of the control head such as Antenna Controller

25 GPIO-2 STATION CONTROLLER SUPPORTED COMMANDS Autoupdate Command AUTOUPDATE,<value> Example //AUTOUPDATE,ON This command turns the autoupdate mode on and off. When on, the autoupdate will send the GPIO board state at a regular interval defined by the INTERVAL command. The values are 1 or ON = turn on autoupdate 0 or OFF = turn off autoupdate Interval This command determines the interval at which the GPIO board update is sent to the master controller. Command INTERVAL,<value> Example //INTERVAL,30 The interval is a number representing approximate number of seconds between updates. Invert digital inputs Command INVERTN,value Example //INVERT2,ON This command will invert the state of a digital input so when it is represented to the master controller a high logic input (+5v) is represented as an off state (RED) as opposed to the normal condition where a logic 1 (+5v) is high and therefore GREEN. Other useful commands //PING Used to pin the GPIO board to make sure it is alive. Ping will return the device address as well. //ROLLCALL Same as ping but with a delayed response based on the device address to allow multiple devices to respond on the network. //SETADDR,x Set the devices network address to x //ECHO,x Return the exact string x //HELP Display the help screen //STATIS Human readable system status.