PDF Using Modbus with Mach3
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1. above in Figure 11shows the state of each of the blocks with the brain As can been seen one of the inputs is active and is shown is Green The corresponding functions block that are also active are shown in green as well Outputs are coloured green or red depending whether they as active or not The status is shown in real time so if a switch is pressed that input will change to green to indicate this The viewer is able to help with the debugging of brains when the system doesn t appear to behave as expected Conclusion Mach3 s integration of Modbus provides a very powerful industrial strength interface which will allow you to control many off the shelf I O devices such as Programmable Logic Controllers PLCs and Variable Frequency Drives VFDs You can use it with devices such as the ModIO to create complex custom I O devices such as Automatic Tool changers and remote Pendants For further information and resources on Modbus applications and hardware a number of resources are listed below Modbus Specification http www modbus org specs ph a Manual d fbbc5a68049baf9e2a51e64192ca79c0 Modbus Customisation examples http www machsupport com MachCustomizeWiki index php title Customization case st udies Mach3 Modbus and Brain Tutorial Videos http www machsupport com videos php Mach3 Support Forum http www machsupport com forum index php2. in Figure 7 is the switches brain It is a very simple brain On the left hand side are the inputs followed by any processing done to the inputs with the result being set into the output on the right hand side E Switches brn Eile View Commands Scroll Help OEH t L No Operation MOD 1 D0 P 0 Upass Signal cle Start No Operation MOD 1 D1 P 0 pass Signal FeedHold No Operation ee MOD 1 D2 P 0 UP ass Signal Figure 7 Switches Brain In the brain above if we look at the third line the input box MOD 1 D2 P 0 specifies e MOD The input is a Modbus input e 1 The 1 register in the Modbus buffer e D2 Data bit 2 is being used Red Switch is connect to this input e P 0 Cfg 0 data buffer is being used The processing or function box which is next shows that the input is just passed through without modification The output Box shows that the output item being written to is the Mach3 Stop File button The other two lines in this brain work in a similar way and the result of all of this e When the Green switch is pressed Cycle Start is activated e When the Blue switch is pressed Feed Hold is activated e When the Red switch is pressed Stop is activated A more complex brain is depicted below in Figure 8 This is for the yellow indicator that is used to indicate when a tool change is occurring and when feed hold is activated EN TowerYellow brn File View Commands Scroll Help
3. shows the setup of the serial port and of the message transfers Along the top you can see that serial port 1 is being used along with the settings of 57600 baud 8 data bits 1 stop bit and no parity Also notice that a timeout of 100ms is configured This means that if the ModIO does not respond to the Modbus request within 100ms Mach3 will assume that it is not going to get a reply and moves on to the next query There is also a checkbox to use RTS for transmit When using a RS232 to RS485 converter it is necessary to tell the converter when Mach3 is transmitting This allows the converter to switch from receive to transmit A bit like pressing the talk button on a walkie talkie One other very important checkbox is the one labelled Modbus Run This needs to be checked for Modbus to work zl Figure 5 above also shows the Message transfers that have been set up We will only be looking at the first two configuration entries namely Cfg 0 and Cfg 1 The other two entries are for a 2 ModIO that we are not concerned with The first configuration Cfg 0 is reading 8 holding registers from a ModIO with a Modbus sub address of 3 The 8 registers in the ModIO start at address 1150 Also they are being read every 50ms a rate of 20 times per second The 2 configuration Cfg 1 is writing a single holding registers to the same ModIO with a Modbus sub address of 3 The register is written to address 1040 It al
4. No Operation Pass Signal No Operation Pass Signal No Operation Pass Signal Partial line hol ToolChange wait MOD 6 D3 P 0 MOD 0 D1 P 1 Figure 8 Tower Yellow Indicator Looking at the inputs we can note the following e Partial Line Hold is used to determine when the G Code is waiting due to Feed Hold being active e ToolChange Wait is used to indicate that the tool change is waiting for the user to press Cycle Start again e MOD 6 D3 P 0 This Modbus input from the ModIO is used to generate a flashing signal from the indicator The register identified by the 6 is a continuously incrementing counter generated by the ModIO Data bit 3 of this register is toggling at a rate of about 2 per second so we can used this as a flashing indicator The processing is a bit more complex that the previous brain The flashing indicator from the ModIO and the Tool change wait signal are ANDed together with the result that we now have a Tool change Wait signal that now is flashing The next function to the right takes the flashing tool change Wait signal and ORs it with the Partial Line Hold signal The output of this block is then set to Bit 1 of the first register in the buffer for Cfg 1 for the Modbus Serial Plugin module This then gets sent to the ModIO and since the yellow indicator is connected to output D1 it will be controlled by this brain So now the Yellow indicator will turn on if the Feedh
5. Overview Query Response Cycle Modbus works on a query response cycle Only the master Mach3 can initiate communication The slaves just respond to the masters queries The master transmits a query frame and one of the slaves ModIO returns a response frame back to the master Each frame that the master sends out contains the address of the slave that it wants the response from It is important to note that the query and response messages all have a known starting and end point This allows the receiver to know when a message has been received if it has been received in full and without error and determine if the message is for them The Query Response cycle is depicted in Figure 4 below Modbus Message Structure Modbus messages are framed to allow the receiver to detect the start and end of the message Modbus RTU uses time gaps of silence to separate the message frames Each message must be preceded with a time gap equivalent to 3 5 characters When the receiver detects this gap after receiving characters it knows that a message has been received and can process it The frame of a Modbus RTU message looks like this Field Description Device address Address of the receiver Function Code Code defining the message type 8 bit Data Bytes Block containing additional data Checksum Checksum to validate message Device Address This identifies who the message is addressed to Valid addresses are 0 247 wit
6. P Modbus Support checkbox is also ticked You only need to tick this one if you are also going to use Modbus devices that communicate over Ethernet You should now exit Mach3 and restart for this part of the configuration to take effect Engine Configuration Ports amp Pins Port Setup and Axis Selection Motor Outputs Input Signals Output Signals Encoder MPG s Spindle Setup Mill Options Port 1 Port 2 MaxNC Mode IV Port Enabled Port Enabled Max CL Mode enabled 0x378 Port Address 0 278 Port Address I Max NC 10 Wave Drive Entry in Hex 0 9 A F only Entry in Hex 0 9 A F only Program restart necessary I Pins 2 9 as inputs on Taa Sherine 1 2 Pulse mod Kernel Speed ModBus InputOutput Supp 25000Hz2 C 35000Hz2 4 M ModBus Plugin Supported C 65000hz 75000hz 100khz l _ TCP Modbus support Event Driven Serial Contra Note Software must be restarted and motors retuned if Fo Sana Seria Link Feedp kernel speed is changed ox e Figure 3 Modbus Module Enable Serial Modbus Configuration For Mach3 to talk to the ModIO shown in Figure 2 above the serial port needs to be configured as does the transfer of data Modbus messages between Mach3 and the ModIO The transfer of Modbus data is best thought of as shared memory between the master and slave Figure 4 below depicts the Modbus Query Response cycle that occurs between Mach3 Mach3 transfers output data to the ModIO and rea
7. Using Modbus with Mach3 By Peter Homann Eventually a new user to Mach3 will hear the term Modbus being bandied about This article explains how it can be used with Mach3 But before diving in and showing how to use it in Mach3 a basic understanding of what Modbus is and how it works is required The Modbus Protocol Modbus is arguably one of the most widely used communication interfaces in industrial control applications It was developed in the late seventies and has stood the test of time The nice thing about the Modbus standard is its flexibility and the ease with which it can be implemented and used Its primary purpose of Modbus is to exchange data between slave devices and a master To put this into context Mach3 is the Master ModIO s VFDs and other devices are the slaves Modbus implements a number of protocols namely serial RTU ASCII and Modbus TCP The serial protocols may be transmitted over standard RS232 and or RS485 interfaces Modbus TCP is transmitted over Ethernet Serial RTU is the most common protocol used with Mach3 although Modbus TCP is gaining popularity Both Protocols may be used simultaneously with Mach3 It should be noted that Serial ASCII is not implemented in Mach3 Figure 1 below illustrates an Architecture Overview of a Mach3 Modbus setup Architecture Overview Modbus Master Mach3 Serial Modbus Sla TCP IP Modbus Slaves ModlO s PLCs ModIP s PLCs Figure 1 Architecture
8. ds back Input data from the ModIO These transfers are done continuously at a rate set by the user to a maximum of 40 times per second The result is that Mach3 continuously gets a copy of the ModIO s inputs switches and the ModIO gets a copy of the status outputs from Mach3 Query Response Cycle Quer Modbus Cfg Data Y Slave Register data Slaves ModlO Master Mach3 Figure 4 Query Response Cycle By continuously transferring the data between Mach3 and the ModIO any spurious data errors will be corrected in the next transfer and will be transparent to the user ModBus Configuration Port Num 1 Baud Rate 57600 8 1 N v T Use RTS for transmit R5485 Timeout 100 ms Test ModBus No error Enabled Comment or PortjAddress Slave Refresh Address of Direction Onjoff Device 0 10 25ms Incr ModBus ar Registers Input Output Cfg 0 1 150 8 Input Halding Cfg 1 1 140 1 Output Holding Cfg 2 1 150 8 Input Holding Cfg 3 1 140 Output Holding Cfg 4 0 Input Reg Cfg 5 1 Input Reg Cfg 6 Input Reg Cfg 7 Input Reg Cfg 8 Input Reg Cfg 9 Input Reg Cfg 10 Input Reg wa S 50 Input Reg cto 12 M ll LE lt 0 Input Reg cy S 0 Input Reg ha 14 B S a A input Reg cio 15 60 Input Reg cons 50 input Reg cto 17_ EDN ln 50 input Reg TET i A r san eee m 7ofro io ool ol ao ol oo GaGa Figure 5 Modbus Message Configuration Figure 5 above
9. espond with a reply Mach3 and Modbus a practical example Figure 2 below depicts a simple example for using a ModIO via Modbus to perform a number of simple Input Output functions Three push buttons will be used to perform the Cycle Start Feed Hold and Cycle Stop input functions On the output side a three indicator light tower will be used to show the mache Mach3 status The ModIO is connected to the PC via the serial port connector In this example Serial Port 1 is used Machine Light Tower Vcom 24Vdc 24Vdc Serial Modbus Slave Light Tower Figure 2 Machine Light Tower Example Mach3 Modbus Configuration In order to use Modbus in Mach3 a number of configurations need to be set up Mach has the ability to support Modbus RTU over a serial interface a TCP IP Ethernet interface or both Additionally for Modbus over a serial line Mach3 has two methods 1 Legacy Modbus Interface 2 Plugin Supported Interface The legacy interface was the initial Modbus interface initially targeting the ModIO device It is no longer the preferred interface and will eventually be removed from Mach3 As such this article will focus on the Plugin Supported Interface The first thing to do in getting Modbus to work is to enable it in the Ports and Pins Configuration page As can be seen in Figure 3 below the checkboxes for Modbus InputOutput Support and Modbus Plugin Supported are both ticked You may also notice that the TC
10. h address O being used as the broadcast address Broadcast messages are a special case and are processed by all slaves with no response message being returned Addresses 1 247 are assigned to individual slave devices When a slave responds to a request it uses the same address that was in the request This allows the master to detect that the slave has responded the request Function Code The function code identifies the message type and the action that is to be performed by the slave The function codes implemented by Mach3 are Data Type Description 01 Read Coils 02 Read Discrete Inputs 03 Read Holding Registers 04 Read Input Registers 15 Write multiple Coils 16 Write multiple Holding Registers The register variables are 16 bit Discretes and coils are single bit values Coils and holding registers may be read and or written to Discretes and Input registers are read only 8 bit data Bytes This block contains any additional information in the message For the read commands it contains the address and the number of registers to read For the write commands it contains the data to be written the number of registers to write the address that the data will be written to Checksum The checksum is a 16 bit CRC code that is used to validate the message The receiver uses this to ensure that the message is not corrupted If the message is deemed to be invalid the receiver just ignores it and does not r
11. old is active Or if Mach3 is waiting for a Tool change the indicator will flash otherwise it will be off Similarly the Green indicator Brain as been written so that the indicator will turn on when G code is running or when waiting for a tool change or feed hold is active In other words the green indicator will be on whenever Mach3 is not in Reset or Stopped E TowerGreen brn File Yiew Commands Scroll Help OEH t No Operation Pass Signal No Operation ToolChange wait U Pass Signal No Operation Partial ine hal H Pass Signal RUN MOD 0 D0 P 1 Figure 9 Green Indicator Brain The Red indicator is used to indicate that RESET is active and will flash the Red indicator when active EN TowerRed brn File View Commands Scroll Help No Operation AND Pass Signal No Operation AND inputs Pass Signal MOD 0 D2 P 1 MOD 6 D3 P 0 Figure 10 Red Indicator Brain Brain Real Time Viewer The Viewer is accessed from the Brains Control Form and can be used to debug a brain as it shows the state of the inputs outputs and processing blocks m BrainView ScrollType Ls r CycleStart 0l o Operation Stop File 0 e MOD 6 D4P 0 OF OEMLED 2000 0J a ToolChange wait 0 MOD 0 D1 T 1 0 OEMLED 2001 0 OEMLED 2001 O MOD 0 D2 T 0 0 Figure 11 Brains Real time Viewer The Viewer depicted
12. so is being written every 50ms a rate of 20 times per second To understand better the contents of the ModIO registers being transferred it is recommended that you read the user manual for the ModIO as it gives a detailed description of each register In Brief register 1040 of the ModIO uses the lower eight bits of the register to represent the state of the 8 ModIO outputs For each of these 8 bits if it is set then the corresponding output will turn on Also register 1150 contains the status of the ModIO s 8 inputs If the input is active the corresponding bit in this register will be 1 The end result of the above configuration is that there is now data being continuously being transferred between Mach3 and the ModIO The status of the 3 switches connected to the ModIO will now reside in the data buffer for Cfg 0 Similarly the contents of the data buffer for Cfg 1 will now be written to the output resister in the ModIO The next step is for Mach3 to process the switch data in the buffer for Cfg 0 and to write the status to the buffer for Cfg 1 so that it can be reflected by the indicators in the Light Tower The processing of this data performed via Mach3 Brains Mach3 Brains The Mach3 brains are a graphical programming environment that allows the user to create programs Brains so as to customise the functionality of Mach3 For our example we need to create a brain to perform the following func
13. tionality When Mach3 is in RESET flash the Red Indicator When Mach3 is in FEEDHOLD turn on the Yellow Indicator When Waiting for a tool change flash the Yellow Indicator When running G code or in FEEDHOLD or waiting for a tool change turn on the Green Indicator AWUN The Brains environment consists of 3 modules e Brains Control Form e Brains Editor e Brains Real Time Viewer A full description on the use of Brains in Mach3 could fill an article in its own right For more detailed description of Brains have a look at the video tutorials on the Mach3 support sight at http www machsupport com videos ph Also have a look through the relevant forum topics on the Mach3 support forum at http www machsupport com forum index php Brain Control Form This Form provides the control to load the brains turn them on and off and to view them in the Brains Real Time Viewer Brain Control Loaded Brains v TowerGreen brn Enabled owerRed brn TowerYellow brn Reload Brain Reload All Brains Enable All Disable all ViewBrain Cancel Figure 6 Brain Control Form For out demonstration you can see four brains one for the switches and one each for the three light tower indicators Breaking up your brain tasks into a number of small brains is a good idea as is cuts down the complexity when working in the Brains editor Brain Editor The editor is where you can create and edit your Brains Depicted below
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