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Basic S-Functions and TLC Coding. Confidential Basic S-Functions and TLC Creating Custom Blocks for Simulink Simulink has the notion of S-functions to.

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Presentation on theme: "Basic S-Functions and TLC Coding. Confidential Basic S-Functions and TLC Creating Custom Blocks for Simulink Simulink has the notion of S-functions to."— Presentation transcript:

1 Basic S-Functions and TLC Coding

2 Confidential Basic S-Functions and TLC Creating Custom Blocks for Simulink Simulink has the notion of S-functions to create user defined blocks S-functions can be written in M, C, or FORTRAN We will focus on C Embedded Coder cannot code generate an S-Function without the help of a TLC (Target Language Compiler) All MotoHawk Blocks are created using S-Functions, Masks, and TLC using interfaces defined by Mathworks No sneaky “special” functions or APIs are used MotoHawk maintains a very thin interface to Simulink to simplify issues that can be caused during Matlab version changes

3 Confidential Help Material S-Functions are Described in the Simulink Help

4 Confidential S-Function Primer Add a S-Function from the Simulink Browser Set the Name and add any parameters Recommend using company_sfun_xxx

5 Confidential S-Function Primer (con’t) Copy \simulink\src\sfuntmpl_basic.c to your local project directory Rename to the same name you chose in the s-function block, in this case mototron_sfun_timesX.c Edit c file: > edit mototron_sfun_timesX.c This must be changed to match filename

6 Confidential Editing the S-Function C File Set the number of Parameters in the function ssSetNumSFcnParams(S, 1); One Parameter

7 Confidential Input Port Definition Set Input Port Attributes

8 Confidential Input Port Direct FeedThrough What does Input Port Direct Feed Through mean? This tells the block sorter that this input port is used as part of the calculation of the output ports Setting it to Zero means that the ports are independent and the sorter does not need to make sure that blocks upstream are calculated first…This is NOT usually the case. Setting it to One means that this input must be calculated prior to the execution of the block. This is USUALLY the case.

9 Confidential Output Port Definition Set Output Port Attributes

10 Confidential Set Options Set Code Generation Options

11 Confidential How Do I Know What Options to Set? \simulink\include\simstruc.h has the documentation

12 Confidential Setting the Sample Time Set to Inherited Sample Time

13 Confidential Creating the Simulation Behavior mdlOutputs contains code for simulation Example to multiply Input by Parameter Value

14 Confidential Build DLL Use Matlab’s mex command to compile file Choose LCC if asked Note resultant file (may be mex32 on newer versions)

15 Confidential Check Simulation Behavior Run in simulation to verify operation

16 Confidential Port Data Types We didn’t specify data types for the ports so they defaulted to double. To accommodate different datatypes requires deeper s- function knowledge

17 Confidential S-Function Wrapup S-function describes the block with respect to the Simulation Engine (and the Diagram Checker) S-Function describes port data types, sizes, number of parameters, sample times, and memory allocations S-Functions contain code that runs in the simulation but that code is not generated into a MotoHawk build, TLC will help us with that S-Function Syntax and Help are contained in Matlab’s Help and simstruc.h

18 Confidential Masks Interacting with the User is defined by a Mask Select S-function block, right click->Mask Subsystem See Matlab Help regarding Mask Details

19 Confidential Add a Parameter Parameters are design time choices needed from the Application Builder Evaluate as a MatLab expression Tunable means adjustable at run time (not available in MotoHawk)

20 Confidential Document on Mask Icon Show the designer’s choice on the block icon for documentation

21 Confidential Add some Help Text Add Mask Help, Copyright Recommended

22 Confidential Mask Wrapup Masks present the custom block to the user Masks can pre-compute via scripts in the Initialization pane Heavy lifting of sorting, querying the model for information, rationalizing the designers choices, etc should be done here. Masks should show as much of the Parameter choices as possible on the icon. Don’t make readers look for data in dialogue boxes Help text should not be overlooked. Too much help documentation is almost enough Good block design should also make the functions and parameters obvious Masks don’t do any code generation but can pre- compute information used by the code generator

23 Confidential TLC Telling the Code Generator What to Do TLC (Target Language Compiler) is the language that drives the Real Time Workshop code generator TLC can be thought of a as a Macro Expansion Language TLC has many computer language constructs like variables, loops, and functions TLC directives use the % sign to indicate that this is a TLC statement Anything without a % sign is either dumped to the current source file or ignored if no file is being created The code generator makes essentially 4 passes over the model to collect code generation directives

24 Confidential TLC Documentation TLC is descibed in Matlab’s Help under Real Time Workshop

25 Confidential TLC File Contents TLC Files Must have an Implements directive and certain “Callback” functions Must match the s- function name and TLC file name Run once if at least one instance of the block is in the model. Typically we add header files here. Note “VOID” means no active output file during this pass Run once for each instance of the block in the model. Note no output active. Usually we add blocks to lists here

26 Confidential TLC File Contents TLC Files Must have an Implements directive and certain “Callback” functions Generate code destined for Startup function Generate code destined for triggered susbsystems.

27 Confidential TLC File Contents Anything without a % directive is dumped to the output

28 Confidential Asking The Code Generator for Names LibBlockInputSignal() and LibBlockOutputSignal ask the code generator for signal names, Parameter[] gets parameter value % expands the TLC variable var into the output Note Constant value is expanded as the literal value. Output is actually a global variable.

29 Confidential Custom Blocks So Far First, we built the S-function DLL from a c file (language #1) Next, we masked the S-Function block to make it look good (language #2) Finally, we wrote a TLC file (language #3) to generated embedded C (language #4). Looking at the generated code, we see some issues A global variable was created when obviously the expression could have been inlined costing no RAM The S-Function C file is terribly complex (and we used the simple template) We can address these two issues by using a better template

30 Confidential A better Approach The MotoHawk Template s-function file contains all of the “Correct” settings for good code generation Simply fill out details at the top, add the simulation behavior and most everything else is taken care of (see motohawk_mex_templ ate.c for the details)

31 Confidential Reuse Outputs and Use Expressions Fix S-Function Options to Re-use outputs (save memory) and Use Expressions if possible Original required two global variables and a run time operation Better version uses stack variable and no run time operation.

32 Confidential Custom Block Wrapup Custom Blocks are Powerful Often times complex Simulink subsystems can be aggregated into a simple block Lower Block count = faster update and compile times Building them requires mastery of 4 languages TLC drives the code generator TLC documentation is readily available in Simulink Look at both MotoHawk and Simulink TLC files for lots of examples Warning, using MotoHawk provided TLC functions may break in the future. We don’t publish that as a public API so we reserve the right to change without notice.

33 Thanks for your attention! MotoTron Corporation

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