How to use Lua scripts

1. General

1.1 Purpose

• This manual helps you create and run Lua scripts on emDrive.
• It also informs you about any warnings and known issues.

1.2 Scope

• The manual covers Lua scripting features, including how to:
  • Download scripts
  • Control scripts
  • Debug scripts
  • Use functions provided by the emDrive library
• It also lists known issues and limitations of the scripting functionality.

1.3 Important Note

• This manual assumes you already know Lua and emDrive Configurator software.
• It is valid for Lua version 5.4. For more details on Lua, visit:
  • Lua 5.4 Manual
  • Programming in Lua

2. emDrive library

2.1 General

The emDrive library is used instead of the standard Lua libraries. This library includes some functions that are identical to those in the standard Lua library, some that have been modified, and others that are unique to emDrive.

Do not overwrite the emDrive library functions and variables.

The emDrive library is organized into different sets, each focused on a specific group of functionalities. This section will describe these sets and their functions and variables in detail.

Here is an example of how to use a library function. This example will show a legend that explains how to read the prototypes of library functions. Words in blue represent variable types, such as arguments or return values. These types follow standard Lua conventions, with the addition of the "integer" type, which represents whole numbers.

When your script calls a function from the emDrive library, the arguments you provide must match the prototype exactly, including the type and, for tables, their structure. If they do not, an error will occur.

number | nil ret1, boolean ret2 = Namespace.FunctionName({integer arg1Field1, string arg1Field2} arg1, 
{integer, integer, integer [5:5-11], integer [13]} arg2, [, string arg3], arg4…)

This is an example of a function named Namespace.FunctionName. It takes in: 2 fixed arguments, 1 optional 
argument and a variable number of arguments. It also returns 2 values where the first can also be nil.

Functions can be called with more arguments then expected in which case excess arguments are ignored.

The emDrive library can raise errors in addition to those raised by the Lua kernel, such as accessing nil values. These library errors usually occur when the type or value of an argument does not match what is expected.

For each function in the emDrive library, the possible errors (exceptions) and the conditions that cause them will be listed.

2.2 Functions

2.2.1 Base

This library provides base script functionality that is not specific to any part of the emDrive hardware (HW) or firmware (FW).

Error(string message [, integer level])

The Error function raises an error with a custom message and specifies the level of the error position. It is useful for throwing exceptions, such as for debugging purposes. This function is equivalent to the standard error() function in Lua and never returns.

2.2.2 I/O

This library works with two main objects: Lua__IO_Input and Lua__IO_Output. These objects facilitate communication between the script and the external world, such as displaying messages or providing debugging arguments to the script.

• Access: These objects can be accessed via the CANopen index 0x2040.
• Purpose:
  • Lua__IO_Input: Used to input data into the script.
  • Lua__IO_Output: Used to output data from the script.

By using these objects, the script can efficiently exchange information with external systems.

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number | string | nil value = IO.Read([option…])

You can read values from the input object using specified options.

Options:

• When the 'n' option is selected, if the value cannot be converted to a number, nil is returned.
• By passing an integer, you can read that many number of characters.

This function is equivalent to the standard io.read() function in Lua.

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IO.Write(string text…)

You can write text to the output object using this function.

• Behavior:
  • If the text is short enough, it is appended to the existing output string.
  • If the text is too long, the existing output string is overwritten.

This function is equivalent to the standard io.write() function in Lua.

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IO.Print(object…)

This function converts an object to a string and then writes the result to the output object.

This function is equivalent to the standard print() function in Lua.

2.2.3 Time

This library provides functions for time keeping and inserting delays in your scripts.

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integer time = Time.GetMs()

This function retrieves the current time in milliseconds since the device was powered on. The maximum value is limited to 2³² – 1.

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Time.WaitMs(integer time)

This function halts the script execution for a specified amount of time using this function.

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integer newStartTime = Time.WaitMsUntil(integer startTime, integer waitTime)

This function halts script execution for specified time from the provided starting time. This function can be used to implement periodic execution independent of logic execution duration.

2.2.3 CAN

This library is used to establish communication and transfer data over CAN. It provides functionality to send and receive CAN messages.

Note: This library does not support CAN FD (Flexible Data-rate).

___________________________________________________________________________________________________________________________________________

This library supports two modes of operation for CAN communication. The mode is selected during the initialization of CAN.

___________________________________________________________________________________________________________________________________________

CAN.Initialize(mode, boolean useExtendedFrame [, integer rxID, integer rxIDMask])

To use CAN communication, initialize CAN with this function. It can be called multiple times with different arguments, but only the last configuration will be used.

• rxIDMask Argument: Required only when the operating mode is set to CAN_RX_TX.

___________________________________________________________________________________________________________________________________________

CAN.Send(integer id, {integer [1:1-8]} data)

Use this function to send a CAN frame with a specified ID and data.

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CAN.Received({integer ID, integer Length, integer Data[1:1-8]} message)

This function is called whenever a CAN message is received.

• User Implementation Required: You must implement this function if CAN is initialized in CAN_RX_TX operating mode.

2.2.4 CANopen

This library is used to interact with the CANopen protocol stack.

• CANopen Object Representation: Internally, a CANopen object is represented as a table with two values: index and subindex.

___________________________________________________________________________________________________________________________________________

The CANopen stack includes a network management state machine that defines the communication behavior of a CANopen device. While there are multiple possible states, only a few are regularly used and available to the user.

___________________________________________________________________________________________________________________________________________

state = CANopen.GetNMTState()

Use this function to retrieve the currently set Network Management (NMT) state of the CANopen device.

___________________________________________________________________________________________________________________________________________

CANopen.SetNMTState(state)

Use this function to request the CANopen stack to change the Network Management (NMT) state of the device.

___________________________________________________________________________________________________________________________________________

number value = CANopen.GetObjectValue({integer, integer} object)

Use this function to retrieve the value of a specified object.

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CANopen.SetObjectValue({integer, integer} object, number value)

Use this function to set the value of a specified object.

2.2.5 Motor

This library is used to operate the motor. You can set operating parameters and retrieve the motor's current state and status.

___________________________________________________________________________________________________________________________________________

The motor can be controlled in three distinct modes. Depending on the chosen mode, the related reference will be used by the motor control algorithm.

___________________________________________________________________________________________________________________________________________

Motor control operates with a state machine that can be in one of multiple states. This state machine is responsible for top-level motor control functions such as initialization, execution, calibration, and error handling.

• State Execution: Some states are executed before the script runs and will not be visible to the user.

___________________________________________________________________________________________________________________________________________

Motor.Enable()

Enable motor control to have the motor operate according to the set mode and the corresponding reference value.

___________________________________________________________________________________________________________________________________________

Motor.Disable()

Disable motor control to stop the motor.

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Motor.Recover()

Use this function to attempt recovery from a motor control error.

Note: This function is only applicable when the motor control is in an error state.

___________________________________________________________________________________________________________________________________________

Motor.SetControlMode(mode)

Use this function to set the motor control mode.

___________________________________________________________________________________________________________________________________________

state = Motor.GetState()

Retrieve the current state of the motor control.

___________________________________________________________________________________________________________________________________________

integer warnings = Motor.GetWarnings()

Retrieve the currently active motor control warnings.

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number velocity = Motor.GetReferenceVelocity()

Retrieve the currently set reference velocity.

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Motor.SetReferenceVelocity(number velocity)

Set the reference velocity.

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number torque = Motor.GetReferenceTorque()

Retrieve the currently set reference torque.

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Motor.SetReferenceTorque(number torque)

Set the reference torque.

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number position = Motor.GetReferencePosition()

Retrieve the currently set reference position.

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Motor.SetReferencePosition(number position)

Set the reference position.

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number velocity = Motor.GetVelocity()

Retrieve the current motor velocity.

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number torque = Motor.GetTorque()

Retrieve the current motor torque.

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number position = Motor.GetPosition()

Retrieve the current motor position.

2.2.6 Digital

This library is used to manipulate digital I/Os (ports). It enables writing to and reading from digital ports.

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Every emDrive contains a set of digital ports that can be freely used by the user application. Some of these ports are writable, while others are read-only. Note that some ports might not be available on all emDrives. To see which ports are available, refer to the manual or the EDS of your emDrive

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number state = Digital.Get(port)

Retrieve the digital state of the port.

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Digital.Set(port, number state)

Set the digital state of the port.

2.2.7 Analog

This library is used to retrieve values from analog inputs (ports).

___________________________________________________________________________________________________________________________________________

Every emDrive contains a set of analog ports that can be freely used by the user application. All of these ports are read-only. Note that some ports might not be available on all emDrives. To see which ports are available, refer to the manual or the EDS of your emDrive.

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number value = Analog.Get(port)

Retrieve the analog value on the port.

3. Scripting

3.1 Setting Up Lua Scripting with Visual Studio Code

To make Lua scripting easier, follow these steps to set up Visual Studio Code with the Lua extension:

1. Install Visual Studio Code

   • If you don't have it yet, download and install Visual Studio Code.

2. Add the Lua Extension

   • Open Visual Studio Code.
   • Go to the Extensions view (click on the square icon on the sidebar or press Ctrl+Shift+X).
   • Search for "Lua" and install the Lua extension by sumneko.
     
     

3. Create a Folder for Libraries

   • Make a new folder on your computer to store the emdrive library. For example, you can name it D:\LuaLibraries.

4. Configure Developer Mode and Add Library Path

   • Open Visual Studio Code.
   • Press Ctrl+P to open the search bar.
   • Type >settings and select "Open User Settings (JSON)" from the list.
     
     
     
     

5. Edit User Settings (JSON)

   • In the opened settings.json file, add the following code.
     

     "Lua.misc.parameters": [
         "--develop=true"
     ],
     "Lua.workspace.checkThirdParty": true,
     "Lua.workspace.userThirdParty": ["path_to_our_library"]

   • Make sure to keep any existing code intact. Add a comma at the end of the last line of the existing code, then paste the new code below it. Update the path to match your folder (D:/LuaLibraries). Use forward slashes instead of backslashes.
     

6. Save and Close

   • Save the changes to settings.json.
   • Close Visual Studio Code.

Example of "settings.json":

3.2 Getting Started with Lua Scripting

3.2.1 Create "firstscript.lua"

1. Create a New Folder

   • Make a new folder for your project.

2. Open the Folder with Visual Studio Code

   • Right-click the folder and select "Open with Code."
     
     
   • This will open Visual Studio Code with your new folder as the workspace.

3. Create a New Lua Script

   • In the Explorer window of Visual Studio Code, right-click and select "New File."
     
     
   • Name the file firstscript.lua (valid files are also "firstscript.txt", "firstscript". But it is better to use .lua which can use our emdrive Library in VS-code).

Note: Only the content of the script is transferred, not the file name.

Limitation: You can store only one script at a time on the emDrive.

3.2.2 Structure

Initialization Routine

• Function Requirement: Your script must include a function named Initialize().
• Execution: This function is the first to run when the script is executed and runs only once.
• Purpose: Use this function to initialize hardware and firmware, such as:
  • Setting up CAN
  • Enabling the motor
  • Setting outputs
  • Setting global variables

Loop Routine

• Function Requirement: Your script must include a function named Loop().
• Periodic Execution: This function runs periodically based on the LoopPeriodMs variable, which represents the period in milliseconds.
  • Setting the Period: LoopPeriodMs can be set globally or within the Initialize() function.
• Purpose: Use the Loop() function for tasks that need regular updates, such as:
  • Setting motor velocity
  • Parsing CAN frames
  • Reading inputs and setting output ports

Minimum Loop Period: The minimum allowed loop period is 10 milliseconds.
Execution Time: Ensure the Loop() function completes within the set period to maintain deterministic execution. If the loop takes longer, it can cause unpredictable behavior.

Priority Consideration: The firmware on the emDrive has higher priority than the script, which means script execution may be interrupted by higher priority tasks.
Use the resource monitor (see the Resource Monitor section) to measure loop duration and determine the minimum possible loop period.
The resource monitor can also show the maximum loop duration when interrupted by higher priority tasks.

Data Transfer: Transferring large data over CAN/CANopen will completely block script execution.

3.3 Executing script

After you've created your script, it is time to download it to emDrive and execute it. For these purposes, a few CANopen objects are provided, as seen in Figure 3. They are grouped together and are accessible at index 0x2040.

Table 52 provides a short description of objects related to script execution. More detailed meanings and use cases will be presented in the following sections.

3.3.1 Download/Upload

• To download the script to emDrive

1. click on Script object (0x2040, 0x5),
2. check “Write from file”,
3. click the “…” button which brings up an open file dialog where you select your script,
4. click “Write” button which will download the script to emDrive,
5. after successful download you should see a green progress bar with “Successful” label.

• To upload the script – this reads back the script currently stored on emDrive:

1. click on Script object (0x2040, 0x5),
2. click the “Read” button which will upload the script from emDrive and display it in the “Description” text box.
   

3.3.2 Control

Once the script has been successfully downloaded and verified, three control options become available through the Control object (0x2040, 0x3).

If a script is already executing when a new script is downloaded, the executing script is terminated as the download is initiated. After the new script is successfully downloaded and verified, it is automatically executed.

NOTE: The script is executed only after motor control has been initialized, which may delay script execution after the device powers on (usually by approximately 100 ms, although this value may vary).

3.3.3 Errors

When an error with the script is detected, the Status object (0x2040, 0x2) is set to a value signaling the type of error. There are four distinct types of errors that are detectable at different stages of script execution:

1. File is non-existent or corrupted (Status = 0): This is set when the script is not stored on the emDrive, or the stored script is corrupted. This error is triggered when script verification fails, either when the device powers on or whenever a new script is downloaded.

2. Compilation failed (Status = 1): This is set when the script could not be compiled, which could be caused by syntax errors or running out of memory. This error is triggered every time script compilation fails, such as when the script is restarted, executed for the first time, or downloaded while another script is already executing, causing the new script to be automatically compiled after downloading.

3. Execution failed (Status = 2): This is set when an error occurs during runtime—such as in initialization, loop, or other required routines—caused by several reasons like accessing nil objects, passing invalid values, missing functions, running out of memory, and others. This error is also raised if the Error() function is called from within the script.

4. Script timed out and was stopped (Status = 6): This is set when the initialization, loop, or other required routines take longer to execute than expected.

The initialization routine must execute within 100 ms, while the loop and other routines are required to execute within 2 × LoopPeriodMs.

Further details of what went wrong with the script can be retrieved from the output object.

All the above-mentioned errors are permanent. When an error is raised, emDrive protection is activated, and emDrive enters an error state from which it cannot recover (refer to the emDrive manual for more details about protections and error states). At this point, the script should be corrected for errors, downloaded to the emDrive, and then the device should be reset to clear the error.

3.3.4 Debugging

There is no proper debugging mechanism in place; however, utilizing Lua I/O objects and general-purpose CANopen objects, some form of limited debugging is possible. Using the input object, the user can control the flow of the program. The user can also write debug information to the output object. Additionally, all objects at index 0x3020, can be used freely for debugging purposes.

3.3.5 Resource monitor

The resource monitor is used to measure characteristics of the script during compile-time, initialization, and runtime (loop). All available objects relevant to resource monitoring are shown under object 0x2031 and described in Table 53.

Initialization and compile-time measurements are performed every time a new script is downloaded and executed or when an existing script is restarted. Memory and loop time monitoring must be explicitly enabled by setting EnableLoopMonitor to 1. This is because these measurements are calculated every loop, thereby shortening the processing time allocated to the script.

3.4 Using the emdrive Library

3.4.1 Option 1: Automatic Setup

1. Add Code to Script

   • In firstscript.lua, add the following line:
     
     

     require('emdrive')

2. Apply Path Modification

   • A pop-up window will appear in the bottom right corner. Click "Apply and modify."
   • After applying, delete the require('emdrive') line.
     
     

3. Check .vscode Folder

   • A new folder named .vscode will be created.
   • Inside, there will be a settings.json file containing the path to the library.

3.4.2 Option 2: Manual Setup

1. Create .vscode Folder

   • Manually create a .vscode folder in your workspace.

2. Create settings.json File

   • Inside the .vscode folder, create a settings.json file.

3. Add Library Path to settings.json

   • Add the following code to settings.json:
     
     

     
     

     {
         "lua.workspace.library": [
             "D:/LuaLibraries"
         ]
     }

4. Examples

4.1 Example 1: "Hello World"

Description:

Print "Hello World" every 100ms to IO_Output.

To make the script work, you need to have two functions: Initialize and Loop.

1. Copy the Code

   Copy the following code to an example.lua file:

   function Initialize()	
   	LoopPeriodMs = 100
   end
   
   function Loop()
       IO.Write("Hello World ")
   end

2. Load the Script on the Inverter

   • Go to 0x2040 0x05 - Script.
   • Select "Write from file" and click "...".
   • A pop-up window will appear. Locate the saved script and click "Open".
   • Click "Write".
     
     
     
     

3. Check if the Script is Valid

   • Go to 0x2040 0x02 - Status.
   • The value "3" indicates the downloaded file is valid.

4. Run the Script

   • Set 0x2040 0x03 - Control to 2.
   • If the script is running, the status value should be "5".

5. View the Output

   • Go to 0x2040 0x07 - IO_output.
   • Click "Read" to see the "Hello World" string in the Description window.
     
     

4.2 Example 2: Data types & variables

4.2.1 Example 2.1: Data types

Lua is a lightweight, high-level programming language known for its simplicity and flexibility. It has several basic data types, each serving a different purpose. Here are the main data types in Lua along with examples for each:

1. Nil
   Represents the absence of a value.
2. Boolean
   Represents a boolean value, either true or false.
3. Number
   Represents both integer and floating-point numbers.
4. String
   Represents a sequence of characters.
5. Table
   Represents associative arrays, which can be used as arrays, dictionaries, or other data structures.
   
6. Function
   Represents a callable function.

function Initialize()	
	LoopPeriodMs = 100
end

function Loop()
    
    -- 1. Nil
    local myVariable = nil
    IO.Print(myVariable)  -- Output: nil

    -- 2. Boolean
    local isTrue = true
    local isFalse = false
    IO.Print(isTrue)  -- Output: true
    IO.Print(isFalse)  -- Output: false

    -- 3. Number
    local integerNumber = 42
    local floatingNumber = 3.14
    IO.Print(integerNumber)  -- Output: 42
    IO.Print(floatingNumber)  -- Output: 3.14

    -- 4. String
    local myString = "Hello, Lua!"
    IO.Print(myString)  -- Output: Hello, Lua!

    -- 5. Table
    local myTable = { key1 = "value1", key2 = "value2" }
    IO.Print(myTable.key1)  -- Output: value1
    IO.Print(myTable.key2)  -- Output: value2

    local arrayTable = { "apple", "banana", "cherry" }
    IO.Print(arrayTable[1])  -- Output: apple

    -- 6. Function
    local function myFunction(a, b)
      return a + b
    end
    IO.Print(myFunction(2, 3))  -- Output: 5
 
    -- 6. Anonymous function
    local anonFunction = function(x, y)
      return x * y
    end
    IO.Print(anonFunction(4, 5))  -- Output: 20

end

4.2.2 Example 2.2: Variables

1. Global variables
   Global variables are accessible from anywhere in the program unless shadowed by a local variable of the same name. By default, any variable declared without the local keyword is global.
   

   myGlobalVariable = 10  -- Global variable
   
   function printGlobal()
     print(myGlobalVariable)
   end
   
   printGlobal()  -- Output: 10

2. Local Variables
   Local variables are only accessible within the block or function where they are declared. They help avoid polluting the global namespace and can be used to manage scope more effectively.
   

   local myLocalVariable = 20  -- Local variable
   
   function printLocal()
     local myLocalVariable = 30  -- Local to this function
     print(myLocalVariable)
   end
   
   printLocal()  -- Output: 30
   print(myLocalVariable)  -- Output: 20

3. Table fields
   Variables can also be fields of tables, allowing for the creation of more complex data structures like arrays, dictionaries, and objects.
   

   local myTable = {
     field1 = "Hello",
     field2 = "World"
   }
   
   print(myTable.field1)  -- Output: Hello
   print(myTable.field2)  -- Output: World

Variable scope

• Global Scope: Variables declared outside of any function or block are global by default.
• Local Scope: Variables declared with the local keyword within a function, block, or loop are local to that block.

1. Global vs. Local
   

   myGlobal = "I am global"
   
   function testScope()
     local myLocal = "I am local"
     print(myGlobal)  -- Accessible
     print(myLocal)   -- Accessible
   end
   
   testScope()
   
   print(myGlobal)  -- Accessible
   -- print(myLocal) -- Error: myLocal is not accessible here

   
   
2. Local Variable Shadowing
   

   local x = 5  -- Local variable in the main chunk
   
   function shadowTest()
     local x = 10  -- Local variable in the function
     print(x)  -- Output: 10
   end
   
   shadowTest()
   print(x)  -- Output: 5

Global variables and tables use a lot of memory, especially in embedded systems. To save memory, it's best to use local variables whenever possible. 
If you use a global variable at the start of your code and don't need it later, clear the global variable to free up memory. You can do this by adding the following code:

myGlobalVariable = nil

4.3 Example 3: Inputs/Outputs

4.3.1 Example 3.1: Use of digital inputs & outputs

Turn low side 1 - ON when switch on digital pin 1 is switched ON.

function Initialize()	
	LoopPeriodMs = 10
end

function Loop()

    local switch = Digital.Get(DIGITAL_IN_1)

    if switch == 1.0 then
        Digital.Set(LOW_SIDE_1, 1)
    else
        Digital.Set(LOW_SIDE_1, 0)
    end
end

4.3.2 Example 3.2: Use of analog inputs

Print analog value of analog input 1 when switch on digital pin 1 is switched ON.

function Initialize()	
	LoopPeriodMs = 10
end

function Loop()

    local switch = Digital.Get(DIGITAL_IN_1)

    if switch == 1.0 then
        local rawVal = Analog.Get(ANALOG_IN_1)
        IO.Print(rawVal)    
    end
end

4.4 Example 4: Blink LED

4.4.1 Example 4.1: Blink LED - "delay"

Loop period is set to 1000ms
LED is connected on low side 1.
Blink LED every 0.5s with Time.WaitMs().

function Initialize()	
	LoopPeriodMs = 1000
end

function Loop()

    local ledState = Digital.Get(LOW_SIDE_1)

    if(ledState == 0.0) then
        Digital.Set(LOW_SIDE_1, 1.0)
    else
        Digital.Set(LOW_SIDE_1, 0.0)
    end

    Time.WaitMs(500)

end

If we set the LoopPeriodMs to 100ms, the script stops running and shows a status of "6", meaning "Script timed out and was stopped."

Here are the key points to understand:

• Time.WaitMs() Function: This function pauses the script for a specified time. In our example, it pauses for 0.5 seconds.
• LoopPeriodMs Setting: We set the script to loop every 100ms.
• Error Explanation: Since the script must loop every 100ms but pauses for 0.5 seconds, it causes an error.

Important Note: Be very careful when using the Time.WaitMs() function to avoid such errors.

4.4.2 Example 4.2: Blink LED - using loop time

We want the LED to blink every 0.5 seconds, while the main loop runs every 10ms. Here's how we do it:

Main_loop_period = 10
Counter = 1


function Initialize()	
	LoopPeriodMs = Main_loop_period
end

function Loop()

    if ((Counter)*Main_loop_period)%500==0 then
    
        local ledState = Digital.Get(LOW_SIDE_1)

        if(ledState == 0.0) then
            Digital.Set(LOW_SIDE_1, 1.0)
        else
            Digital.Set(LOW_SIDE_1, 0.0)
        end

    end
 
    if Counter<50 then
        Counter=Counter+1
    else
        Counter=1
    end

end

4.4.3 Example 4.3: Blink LED - using processor time

The script initializes a start time variable and defines two functions. In the Loop function, the script checks if the StartTime is nil and if so, sets it to the current time in milliseconds.
The Loop function then continuously gets the current time in milliseconds. If 500 milliseconds have passed since the StartTime, it resets the StartTime to the current time.
It then gets the state of a digital output LOW_SIDE_1.
If LOW_SIDE_1 is off (state is 0.0), it turns it on (state to 1.0).
If LOW_SIDE_1 is on (state is 1.0), it turns it off (state to 0.0).

This process repeats every 500 milliseconds, toggling the state of LOW_SIDE_1 each time.

StartTime = nil

function Initialize()	
	LoopPeriodMs = 10
end

function Loop()

    --Execute only once at the start of the loop
    if(StartTime == nil) then
        StartTime = Time.GetMs()
    end

    --Chechk every loop what is the time
    local CurrentTime = Time.GetMs() 

    if (CurrentTime - StartTime >= 500) then
        StartTime = CurrentTime

        local ledState = Digital.Get(LOW_SIDE_1)

        if(ledState == 0.0) then
            Digital.Set(LOW_SIDE_1, 1.0)
        else
            Digital.Set(LOW_SIDE_1, 0.0)
        end

    end
end

4.5 Example 5: CAN send

4.5.1 Example 5.1: (CAN send simple message)

To send a CAN message every 100ms with an ID of 0x205 and data value 500 using the first 2 bytes, follow these steps: 

1. Use Template:

   • Start with example 4.3 as a template.

2. Add Variables and Functions:

   • Define a CanID variable.
   • Initialize CAN with the CAN.Initialize() function.

3. Sending Parameters:

   • Use the CAN_TX_ONLY parameter for sending.
   • Messages will not be extended.
   • Set filters to 0 since we are only sending.

4. Modify the Code:

   • Delete the code for toggling the output.

5. Create Custom Function:

   • Create a function that is called every 100ms.
   • Name the argument Data_raw.
   • Split Data_raw into 2 bytes.
   • Send the data using the CAN.Send() function.

CanID = 0x205

StartTime = nil

function Initialize()

    CAN.Initialize(CAN_TX_ONLY,false,0,0)

	LoopPeriodMs = 10
end

function Loop()

    --Execute only once at the start of the loop
    if(StartTime == nil) then
        StartTime = Time.GetMs()
    end

    --Chechk every loop what is the time
    local CurrentTime = Time.GetMs() 

    if (CurrentTime - StartTime >= 100) then
        StartTime = CurrentTime
        SendData(500)
    end
end

function SendData(Data_raw)
    local val = Data_raw
    local byte0 = math.floor(val) & 0xFF
    local byte1 = (math.floor(val) & 0xFF00) >> 8
    CAN.Send(CanID,{byte0,byte1,0,0,0,0,0,0})
end

4.5.2 Example 5.2 : CAN send extended message (J1939)

We will do the same as in example 5.1 except we will send an extended message (It will be a J1939 message PH3 - the data order might be different in the standard).

 
ID = 0x18FF8203. 

The only thing we need to change is 2 lines, we need to change the CanID and in the CAN.Initialize() function, the boolean value to true. If we change only the CanID then the message will still be sent out but the ID will be 0x199 (last 3 digits of - ID 0x18FF8199).

CanID = 0x18FF8199
CAN.Initialize(CAN_TX_ONLY,true,0,0)

4.6 Example 6: CAN receive

4.6.1 Example 6.1 : CAN receive

In this example we will turn ON and OFF a LED that is connected on low side 1 with a received can message.
The Can ID has to be 0x123 and we will send only one byte of data. If the value of data is 1 then the LED will be turned ON, otherwise it will be turned OFF. 
 
To use the CAN receive function we need to change the CAN.Initialite() and add a function called "CAN.Received(message)". With the following code we always go into the CAN.Received() function when a message is received and then we check if the ID is correct.

function Initialize()
    CAN.Initialize(CAN_RX_TX,false,0,0)
	LoopPeriodMs = 10
end

function Loop()


end

function CAN.Received(message)
    if (message.ID == 0x123) then
        IO.Print(" Data1: ", message.Data[1])
        if(message.Data[1] == 1) then
            Digital.Set(LOW_SIDE_1, 1.0)
        else
            Digital.Set(LOW_SIDE_1, 0.0)
        end
    end
end

We can also add a filter so we only go into the CAN.Received() when the message has a proper ID. We achieve this with the following code.

function Initialize()
    CAN.Initialize(CAN_RX_TX,false,0x123,0x123)
	LoopPeriodMs = 10
end

function Loop()


end

function CAN.Received(message)
    --if (message.ID == 0x123) then
    IO.Print(" Data1: ", message.Data[1])
    if(message.Data[1] == 1) then
        Digital.Set(LOW_SIDE_1, 1.0)
    else
        Digital.Set(LOW_SIDE_1, 0.0)
    end
    --end
end

4.7 Example 7: Read & Set CANopen objects

In this example, we'll use an analog input (HW AIN1) as a throttle to set the motor velocity reference (object 0x3010 0x05). We will also read this object and print its value to the Lua output. Additionally, we'll limit the maximum RPM using the math library to prevent the motor from running away if there's a problem with the analog reading.

0V = 0RPM
5V = 200RPM

For this example to work you need an inverter that is configured to work with the connected motor. You need to be first able to spin it in velocity mode using the configurator.
When you start the script go to operational and turn on PWMs manually.

If the analog throttle is damaged (either a short circuit or a broken circuit), there is no safety system in place. Here’s what can happen:

If the circuit is broken, no voltage will be applied, and the RPM will be 0.
If there is a short circuit, the inverter will receive the full 5V on the analog input, causing the RPM to go to the maximum.

To prevent these issues, we need to add safety features. These will be demonstrated in Example 8.

VelocityRef = {0x3010, 0x05}

function Initialize()
	LoopPeriodMs = 10
end

function Loop()
   

    local rpm = Analog.Get(ANALOG_IN_1) * 40
    rpm = math.min(rpm,200)

    CANopen.SetObjectValue(VelocityRef, rpm)
    
    local VelRef_from_CANopen = CANopen.GetObjectValue(VelocityRef)

    IO.Print(VelRef_from_CANopen)
end

4.8 Example 8: Demo application

4.8.1 Example 8.1 : Demo application using CANopen objects.

In this example, we will demonstrate how to use the HW AIN1 input for a simple throttle control with a potentiometer (0-5V).

• Throttle Input: HW AIN1 (0-5V Potentiometer)
  • Minimum RPM: 0 (corresponds to 0.5V)
  • Maximum RPM: 200 (corresponds to 4.5V)
  • Motor Stop Conditions:
    • If the throttle voltage is below 0.2V or above 4.8V, the motor will stop to protect against short and break issues.
  • PWM Enable Condition:
    • If the throttle voltage is below 0.5V, the PWM signals will be enabled

function Initialize()

    CANopen.SetObjectValue(VelocityRef, 0) -- Set Velocity ref to 0
	CANopen.SetObjectValue(ControlMode, 1) -- Set velocity mode
	CANopen.SetNMTState(CO_OPERATIONAL)    -- Go into operational mode

	LoopPeriodMs = 100
end

function Loop()
    local throttleVoltage = Analog.Get(ANALOG_IN_1)
    -- Decide whether to enable or disable the motor
    if Digital.Get(DIGITAL_IN_1) == 1 then
        -- only enable if voltage on analog in 1 is < 0.5 V so the motor does not start ang goes to high RPM
        if (throttleVoltage < 0.5) then
            CANopen.SetObjectValue(PwmControl, 1)
        end
    else
        CANopen.SetObjectValue(PwmControl, 0)
    end

    if (throttleVoltage > 0.2 and throttleVoltage < 4.8) == true then
           -- Map values 0.5 - 4.5 V to 0 - 200 RPM and
            local rpm = (throttleVoltage - 0.5) / 4 * 200
            rpm = math.min(rpm, 200)
            rpm = math.max(rpm, 0)
            CANopen.SetObjectValue(VelocityRef, rpm)
    else
        CANopen.SetObjectValue(VelocityRef, 0)
        CANopen.SetObjectValue(PwmControl, 0)
    end
end

4.8.2 Example 8.2 : Demo application using dedicated motor library.

In this example we will have the same functionality of the code as in example 8.1. but with the use of motor library
With the use of the motor library the code is easier to read and write than example 8.1.

function Initialize()

    Motor.SetReferenceVelocity(0)       -- Set Velocity ref to 0
	Motor.SetControlMode(VELOCITY_MODE) -- Set velocity mode
	CANopen.SetNMTState(CO_OPERATIONAL) -- Go into operational mode

	LoopPeriodMs = 100
end

function Loop()
    local throttleVoltage = Analog.Get(ANALOG_IN_1)
    -- Decide whether to enable or disable the motor
    if Digital.Get(DIGITAL_IN_1) == 1 then
        -- only enable if voltage on analog in 1 is < 0.5 V so the motor does not start ang goes to high RPM
        if (throttleVoltage < 0.5) then
            Motor.Enable()
        end
    else
        Motor.Disable()
    end

    if (throttleVoltage > 0.2 and throttleVoltage < 4.8) == true then
           -- Map values 0.5 - 4.5 V to 0 - 200 RPM and
            local rpm = (throttleVoltage - 0.5) / 4 * 200
            rpm = math.min(rpm, 200)
            rpm = math.max(rpm, 0)
            Motor.SetReferenceVelocity(rpm)
    else
        Motor.SetReferenceVelocity(0)
        Motor.Disable()
    end
end

4.9 Example 9: Throttle script (state - machine)

Throttle Control

• Adjusting the Throttle: Use the potentiometer connected to Analog_IN_1.
• Protection: The potentiometer is protected against short and break circuits.
• Deadband: A deadband of 0.3V is set for the potentiometer.
• Speed Limits:
  • Minimum speed: 0 RPM
  • Maximum speed: 300 RPM

Motor Operation

• Activation:
  • The motor runs only when digital pin 1 (ON/OFF switch) is connected.
  • Change motor direction using a switch on digital pin 3.
• Speed Setting:
  • Forward max speed: Object 0x3020 0x0D
  • Reverse max speed: Object 0x3020 0x0E
  • Switching direction at max speed changes to the corresponding reverse speed.

LED Diagnostics

• LED Indicator (HS1):
  • On: System working normally.
  • Blinking: System in error mode.
• Error Blink Codes:
  • Error 2: Blinks twice, then pauses.
  • Error 3: Blinks three times, then pauses.

Voltage and RPM Details

• Working Voltage Range:
  • Minimum RPM: at 0.5V
  • Maximum RPM: at 4.5V
  • Deadband: 0.3V
• Error Conditions:
  • ERROR1: Voltage out of bounds
  • ERROR2: Analog_IN_1 < (Min_Volt - Deadband)
  • ERROR3: Analog_IN_1 > (Max_Volt + Deadband)

CANopen Error Messages

• Error Message (0x80 + nodeID):
  • Sent every 100ms in error state.
  • Data length: 8 bytes.
  • Byte 0 Mapping:
    • Bit 0: Throttle potentiometer error out of bounds
    • Bit 1: Throttle potentiometer break circuit error
    • Bit 2: Throttle potentiometer short circuit error
• Warning Message (0x180 + nodeID):
  • Sent every 100ms in start state.
  • Data length: 8 bytes.
  • Byte 0: Warning code 0x01 (Motor disabled, potentiometer not in min position)

If the motor spins at Forward max speed and you switch the direction with the switch then it will spin at Reverse max speed

-- Limits
MAX_RPM = 300
MIN_RPM = -300

-- Objects
FORWARD_MAX_SPEED_ID = {0x3020, 0xD}
REVERSE_MAX_SPEED_ID = {0x3020, 0xE}
LED_ID 				 = {0x30A4, 0x02}


-- Inputs
ENABLE_SW 	 = DIGITAL_IN_1
DIRECTION_SW = DIGITAL_IN_2
THROTTLE_IN  = ANALOG_IN_1
DIRECTION_IN = DIGITAL_IN_3


-- Voltage thresholds
THROTTLE_MIN_V = 0.5
THROTTLE_MAX_V = 4.5
DEADBAND 	 = 0.3


ERROR	  = 0
ERROR_reg = 0
WARNINGS  = 0


StartTime1	= nil
StartTIme2	= nil
StartTime3 	= nil
StartTime4 	= nil
FlagCounter = 0


DIN		  = {ON = 1, OFF = 0}
LED 	  = {OFF = 0x0, ON = 0x1}
DIRECTION = {FORWARD = 1, REVERSE = 0}

-- Application FSM
Application = {}


function Initialize()
	CAN.Initialize(CAN_TX_ONLY,false,0,0)

	Application.NextState = "Idle"

    Motor.SetReferenceVelocity(0)
	Motor.SetControlMode(VELOCITY_MODE)

	LoopPeriodMs = 10
end


function Loop()
	Application[Application.NextState]()
end


Application.Idle = function ()
	CANopen.SetObjectValue(LED_ID, LED.ON)
	CANopen.SetNMTState(CO_OPERATIONAL)
	Application.NextState = "Start"
end


Application.Start = function ()


    -- IF enable switch is off go to stop state
    if (Digital.Get(ENABLE_SW) == DIN.OFF ) then
		Application.NextState = "Stop"
		return
	end


    -- Get voltage
	local throttleVoltage = Analog.Get(THROTTLE_IN)


    -- Go into error state if throttle voltage is out of bounds
    if OutOfBounds(throttleVoltage, (THROTTLE_MIN_V - DEADBAND), (THROTTLE_MAX_V + DEADBAND)) == true then
		ERROR = (ERROR or 0) | 1
		Application.NextState = "Error"
		return
	end


    -- Check that voltage is bellow minimal throttle voltage - so that the motor does not start at high speed
	if Motor.GetState() == MOTOR_OFF then
		if throttleVoltage < (THROTTLE_MIN_V) then
            Motor.Enable()
			WARNINGS = WARNINGS & Negate_Xbit(1, 8)
            return
		else
			WARNINGS = (WARNINGS or 0) | 1
        end
	end

	-- Only set velocity reference when pwms are enabled
	if ((Motor.GetState() == MOTOR_RUN) and (throttleVoltage >= 0.5)) then
		-- Calculate Voltage
    	--local rpm = ((throttleVoltage - THROTTLE_MIN_V) * MAX_RPM) / (THROTTLE_MAX_V - THROTTLE_MIN_V)
		local rpm = ((throttleVoltage - THROTTLE_MIN_V) * GetMaxSpeed()) / (THROTTLE_MAX_V - THROTTLE_MIN_V)
    	-- Limit RPM
    	rpm = math.min(rpm, MAX_RPM)
    	rpm = math.max(rpm, MIN_RPM)
		IO.Print("REF: ", rpm)
    	-- Set ref
		Motor.SetReferenceVelocity(rpm)
	end

	-- Send warnings every 100ms
	local CurrentTime = Time.GetMs()
	if((StartTIme2 == nil) or (CurrentTime-StartTIme2) >= 100) then
		SendWarnings()
	end
end


Application.Stop = function ()
    Motor.SetReferenceVelocity(0)
	Motor.Disable()
    --When eneble sw is activated go to start state
	if (Digital.Get(ENABLE_SW) == DIN.ON) then
		Application.NextState = "Start"
	end
end

Application.Error = function ()

    Motor.Disable()
	Motor.SetReferenceVelocity(0)

	--local ledValue = CANopen.GetObjectValue(LED_ID)
    local throttleVoltage = Analog.Get(THROTTLE_IN)
	local ErrorBlinkCounter = 0
	local CurrentTime

	--If bit 0 = 1 then OutOfBounds is detected
	if (ERROR & 1) == 1 then
		if throttleVoltage < (THROTTLE_MIN_V - DEADBAND) then
			ERROR = ERROR | 2
			ERROR_reg = ERROR_reg | 1 -- set the generic error register
		elseif throttleVoltage > (THROTTLE_MAX_V + DEADBAND) then
			ERROR = ERROR | 4
			ERROR_reg = ERROR_reg | 1 -- set the generic error register
		else
			-- Clear ERROR bit 0, 1, 2
			ERROR = ERROR & Negate_Xbit(7, 16)
			-- Clear the generic error register
			ERROR_reg = ERROR_reg | Negate_Xbit(1, 8)
		end
	end

	-- Send Errors every 100ms
	CurrentTime = Time.GetMs()
	if ((StartTime1 == nil) or (CurrentTime - StartTime1) >= 100) then
		StartTime1 = CurrentTime
		SendError()
	end

	-- Determine how many times we want to blink the led
    if ((ERROR & 2) >> 1) == 1 then
        ErrorBlinkCounter = 2
    elseif ((ERROR & 4) >> 2) == 1 then
        ErrorBlinkCounter = 3
    end

    -- Start the blinking cycle if enough time has passed
	CurrentTime = Time.GetMs()
    if StartTime3 == nil or (CurrentTime - StartTime3) >= 3000 then
        StartTime3 = CurrentTime
        FlagCounter = 0
    end

    -- Handle the blinking logic
    if FlagCounter < 2 * ErrorBlinkCounter then
        if StartTime4 == nil or (CurrentTime - StartTime4) >= 300 then
            StartTime4 = CurrentTime
            FlagCounter = FlagCounter + 1

            -- Toggle LED
            --if ledValue == 0  then
            if FlagCounter % 2 == 1 then
				CANopen.SetObjectValue(LED_ID, LED.ON)
            else
                CANopen.SetObjectValue(LED_ID, LED.OFF)
            end
        end
	else
		-- Ensure the LED is off during the pause period
        CANopen.SetObjectValue(LED_ID, LED.OFF)
    end

    if ERROR == 0 then
		FlagCounter = 0
		Application.NextState = "Idle"
		return
	end
end


function GetMaxSpeed()
	if Digital.Get(DIRECTION_IN) == DIRECTION.FORWARD then
		return CANopen.GetObjectValue(FORWARD_MAX_SPEED_ID)
	end
	return CANopen.GetObjectValue(REVERSE_MAX_SPEED_ID)
end


function SendError()
	-- Send on ID + nodeID; we get the NodeId from CANopen off the inverter
	local CanID = 0x80 + CANopen.GetObjectValue({0x100B, 0x00})
	local byte0 = ERROR & 0xFF
	local byte1 = (ERROR & 0xFF00) >> 8
	local byte2 = ERROR_reg & 0xFF
	CAN.Send(CanID,{byte0, byte1, byte2, 0, 0, 0, 0, 0})
end

function SendWarnings()
	-- Send on PDO + nodeID;
	local CanID = 0x180 + CANopen.GetObjectValue({0x100B, 0x00})
	local byte0 = WARNINGS & 0xFF
	CAN.Send(CanID,{byte0, 0, 0, 0, 0, 0, 0, 0})
end


function OutOfBounds(throttleVoltage, minVal, maxVal)
    if (throttleVoltage < minVal) or (throttleVoltage > maxVal) then
        return true
    else
        return false
    end
end


--- Fuctino to negate bits
---@param value number Value to negate
---@param xBit number Number of bites e.g 16bit => xBit = 16
function Negate_Xbit(value, xBit)
    local negated = 0
    for i = 0, (xBit - 1) do
        if (value & (1 << i)) == 0 then
            negated = negated + (1 << i)
        end
    end
    return negated
end

5. Benchmark

	RAM usage [kB]	RAM free [kB]	Avg. loop duration [us]	Compile time [ms]	Initialization time [ms]
00Empty_script	12	24	13	2.7	0.175
01GetObject	11.728	24.112	5000	2.9	0.173
02GetObject_with_library	11.784	24.056	510	2.94	0.241
03GetSet	12.088	23.752	5000	3.178	0.177
04GetSet_with_library	12.128	23.712	450	3.149	0.174
05Timer_example_4_1	12.064	23.776	500407	3.294	0.242
06Timer_example_4_2	12.200	23.640	17	3.669	0.177
07Timer_example_4_3	12.232	23.608	19	3.747	0.175
08Example_5	12.104	23.736	18	4.332	0.213
09Example_6	15.512	20.328	9	3.468	0.225
10Example_7	22.048	12.792	125	3.506	0.191
11Example_8.1	13.472	22.368	110	5.030	0.293
12Example_8.2	13.072	22.768	50	4.628	0.250
13Example_9	21.112	14.728	250	15.756	0.742

6. Best practices

For further insights and practical tips, I recommend exploring "Programming in Lua," available at: Programming in Lua. Authored by experts in the field, this comprehensive resource offers invaluable guidance for Lua developers. It's worth noting that the entire topic is accessible free of charge as of April 24, 2024. Additionally, some sections of the topic include examples to further illustrate key concepts and techniques.

6.1 Minimizing Global Variables

In Lua scripting, it's imperative to exercise caution with global variables to prevent memory exhaustion and script failures, especially on embbeded systems. Emphasizing the utilization of local variables whenever possible is paramount. By minimizing global variable usage, we mitigate the risk of memory overflow and enhance script performance.

Example:

myGlobalVaribale = 10  --Global variable
local myLocalVaribale = 10  --Local variable

7. Known issues and limitations

This section describes known issues and limitations, their causes, and solutions or mitigations if they exist.

7.1 Issues

7.1.1

Error 0x06070010 when loading a script may indicate Lua object 0x2040 0x01 isn't set to 1. To resolve, ensure proper access level in Configurator to unlock this feature. If you do not have the proper access level contact us.

 

7.1.2 Output object out of memory error

When reading an output object whose value is periodically changing by the script, it is possible that an "Out of memory" error, as shown in Figure 8, may be reported by the emDrive Configurator.

Cause: unsynchronized reading and writing to output object by script and emDrive Configurator at the same time.

Solution: read output object again.

 

7.1.3 IO.Print() isn't functioning

If IO.Print() isn't functioning, it may signal an outdated firmware version. Firmware 0x10C01 lacks support, while 0x10D02 enables the function.

 

7.1.4