Chapter 4 DSP/BIOS

Chapter 4 DSP/BIOS Part 1 - Introduction

Learning Objectives Introduce DSP/BIOS and its components. Introduce the software tools for managing DSP/BIOS components and objects. Run some examples.

DSP/BIOS The DSP/BIOS is an operating system that can provide: A graphical interface for static system setup. Real-time scheduling. Real-time analysis (RTA). Real-time data exchange (RTDX).

DSP/BIOS Components The user writes code (‘C’/assembly) using the DSP/BIOS library. The user can use the configuration tools to setup the system. All the files generated constitute a project.

DSP/BIOS Components The project is then compiled, assembled and linked by the code generation tools in order to generate an executable file (*.out). There are also some DSP/BIOS plug-ins that can be used, for instance, as program test while the target is running.

DSP/BIOS Components Code composer simulator/debugger and the host emulator support are also part of the code composer studio. The host and target communicate through the JTAG (Joint Test Action Group) connection (ssya002c.pdf).

Graphical Interface for Static System Setup Static system setup is performed using the DSP/BIOS GUI configuration tool. The configuration tool has an interface similar to windows explorer. It lets you: Specify a wide range of parameters used by the DSP/BIOS real-time library. Create run-time objects that are used by the target application’s DSP/BIOS API calls. Note: API: Application Programming Interface

Graphical Interface for Static System Setup The DSP/BIOS main objects are: (1) Hardware interrupts (HWI). (2) Software interrupts (SWI). (3) Tasks (TSK, IDL). (4) Data and I/O streams (RTDX, SIO, PIP, HST). (5) Synchronisation and Communication (SEM, MBX, LCK). (6) Timing (PRD, CLK). (7) Logging and statistics (LOG, STS, TRC). For a complete list see: \Links\SPRU303.pdf (Page 1-5).

Graphical Interface for Static System Setup How to create a configuration file: Open CCS and create a new project and name it “lab1.pjt”. Create a new configuration file by using a pre-built template file: File:New:DSP/BIOS Configuration

Graphical Interface for Static System Setup How to create a configuration file: Double click on the “dsk6711.cdb” icon and the following configuration will appear:

Graphical Interface for Static System Setup How to create a configuration file: Now that you have selected the template, save it in your current working directory, e.g: Code\Chapter4 - DSP_BIOS\Lab1\lab1.cdb. Finally, add the “*.cdb” configuration file to the project.

Graphical Interface for Static System Setup Files created by the configuration tools: Once the lab1.cdb file is modified, saved and added to the project, the configuration manager will create and load the following files: lab1cfg.s62 Assembly file lab1cfg_c.c C file lab1cfg.h Header file for C lab1cfg.h62 Header file for assembly A file called “lab1cfg.cmd” is also created but must be loaded by the user. Note: the user must add the *.cdb and *.cmd files to the project.

Graphical Interface for Static System Setup Files used to create the DSP/BIOS program: The abbreviation 62 is used for the C6000 processors. Programs/Files generated by the configuration manager Programs generated by the user

Chapter 4 DSP/BIOS Part 2 - Real Time Scheduling

Learning Objectives What is a real-time scheduler? Why do we need a real-time scheduler? DSP/BIOS Thread Types. Example.

Real-time scheduling Before embarking into real-time scheduling let us first state the problem: main () { for (;;); } ISR1() algorithm1(); ISR2() algorithm2(); Once ISR1 or 2 is called, algorithm 1 or 2 runs to completion. Can this cause a problem?

Real-time scheduling Before embarking into real-time scheduling let us first state the problem: main () { for (;;); } ISR1() algorithm1(); ISR2() algorithm2(); There is no guarantee of meeting the real-time deadlines because: (1) The algorithms can run at different rates. (2) One algorithm can overshadow the other. (3) The timing can be non-deterministic. etc. Once ISR1 or ISR2 is called, algorithm 1 or 2 runs to completion. Can this cause a problem?

Real-time scheduling The answer depends on the application. If we want to process two algorithms in real-time then we have to answer the following questions: Are ISR1 and ISR2 synchronised? If yes, then we can use only an ISR that processes both algorithms (assuming that we have enough processing power to complete algorithm 1 and 2 on time). What happens if the algorithms are not synchronised? Which algorithm has a higher priority? Can the algorithm of lower priority be pre-empted (stopped)?

CPU processing Algorithm 1 CPU processing Algorithm 2 Real-time scheduling Example: Simple application. System description: Algorithm 1 and 2 are not synchronised. Assume algorithm 1 has the highest priority. Algorithm 2 can be pended. CPU processing Algorithm 1 MISSED! Algorithm 1 Algorithm 2 CPU processing Algorithm 2 Remember: there is only one CPU and therefore only one algorithm can be processed at a time.

Real-time scheduling Example: Simple application. Solution 1: Algorithm decomposition: The algorithm can be decomposed into sub-functions: When the CPU is not processing algorithm1 it can process one of the sub-functions (to completion) as shown: algorithm2 (); function1(); function2(); function3(); Algorithm 1 Algorithm 2 function1 function2 function3

Real-time scheduling Example: Simple application. Problems with this solution: Difficult to write (as timing is critical). Difficult to change (what happens if algorithm is modified or another algorithm is added).

Real-time scheduling Example: Simple application. Solution 2: Using an operating system Advantages: Easy to write (algorithms are written independently). Easy to maintain or change (operating system takes care of the scheduling). Enables fast time to market. Which operating system? Depends on: The processor being used. The DSP platform (single/multi processors).

Real-time scheduling: DSP/BIOS For all TI DSPs there is a DSP/BIOS operating system which includes: Small sized real-time library. An API for using the library services. Easy-to-use configuration tools. Real-time analysis programs. DSP/BIOS scheduling solution provides: Fixed-priority preemptive scheduler. Multiple thread types.

Real-time scheduling: Terminology No preemption: Resources cannot be preempted; which means that the only way of releasing a resource is by the process of holding it. Object: Term for data and code structures provided by DSP/BIOS, e.g. an event, task, semaphore. Pend: Wait for an event Resource preemption: Release of a resource. Post: Signal an event, e.g. post a software interrupt, that is make a software interrupt ready. Preemption: A higher priority function (or thread) interrupts other functions (or threads) of lower priority. Priority scheduling: Priority scheduling can be either preemptive or non-preemptive. A preemptive priority scheduling algorithm will preempt (release) the CPU if another process of higher priority arrives. Process: A task or thread of execution. Scheduler: System software to manage the execution of threads. Scheduling: The planning used to share a resource. Semaphore: Synchronisation system object that enables tasks to synchronise their activities. Thread: An independent function.

DSP/BIOS Thread Types Priority HWI HWI priorities set by hardware Hardware Interrupts HWI priorities set by hardware One ISR per interrupt. SWI Software Interrupts 14 SWI priority levels Multiple SWIs at each level. TSK Tasks 15 TSK priority levels Multiple TSKs at each level. IDL Background Multiple IDL functions Continuous loop. HWI triggered by hardware interrupt. IDL runs as the background thread. What causes a SWI or TSK to run?

Triggering SWI or TSK SWI start end SWI_post TSK start end block “run to completion” TSK SEM_pend start end block SEM_post SWI cannot pend. SWI always returns from function. TSK only returns when no longer needed, otherwise normally an infinite loop.

Considerations in Selecting Thread Types Thread latency and data rates. Multi-tiered response to interrupts: HWI is fast (for sample-by-sample response time). SWI is slower (triggered to process frame). Priority of thread. Stack needs: O.K. to share system stack? then use SWI. Need private stack? then use TSK. Synchronization and communication methods: SWI and TSK have different methods. User preference or ease-of-use.

Thread Preemption Example post swi1 post swi2 post sem2 post swi2 return return return return HWI post sem1 post sem2 return SWI 2 return return SWI 1 pend sem2 pend sem2 pend sem2 interrupt TSK 2 pend sem1 pend sem1 TSK 1 interrupt interrupt main() return IDL interrupt Events over time

Laboratory Exercise Laboratory objectives: (1) Set the internal timer 1 to generate ticks at 8kHz. (2) Set a hardware interrupt that is triggered by internal timer 1. (3) Create a software interrupt that can be posted by the hardware interrupt. (4) Create a task that can be posted by the hardware interrupt. (5) Create a semaphore that can be used by the task functions.

(1) Setting Internal Timer 1 (1) Create a new project and call it “bios_lab.pjt”. (2) Add the “dsk6711.cdb” file (see slide 10) and rename it “bios_lab2.cdb”. (3) Set a timer configuration by using the “Timer Configuration Manager” and call it “timerCfg0” and set the properties: The GUI interface will generate the “bios_labcfg.c”, see \Links\bios_labcfg.pdf

(2) Setting the Hardware Interrupt (1) Open the CDB file. (2) Select the “HWI - Hardware Interrupt Service …”. (3) Select HWI_INT15 and right click to select properties. Source = Timer_1 Function = _timerIsr

(2) Setting the Hardware Interrupt (4) Write the Interrupt Service Routine in C. void timerIsr (void) { /* Put your code here */ }

(3) Creating a Software Interrupt (1) Open the cdb file and select the “SWI - Software Interrupt Manager” and create a new software interrupt called “SWI_for_algorithm_1”.

(3) Creating a Software Interrupt (2) Change the properties of the “SWI_for_algorithm_1” to:

(3) Creating a Software Interrupt (3) Create a software interrupt function in C. void algorithm_1 (void) { /* Put your code here */ }

(4) Creating a Task (1) Open the cdb file and select the “TSK - Task Manager” and create a new task called “TaskOneTsk”.

(4) Creating a Task (2) Change the properties to:

(4) Creating a Task (3) Create a task function in C: void ProcessTask (void) { /* Put your algorithm here */ }

(5) Creating a Semaphore (1) Open the cdb file and select the “SEM - Semaphore Manager” and create a new semaphore called “taskOneSem”. (2) Change the properties of the “taskOneSem” to:

Posting Software Interrupts and Tasks The software interrupts can be posted simply by writing: SWI_post (&SWI_for_algorithm_1); (2) Tasks The task can be removed from semaphore queue and put it on the ready queue: SEM_post (&taskOneSem);

More on Tasks… A task can be pending where as Software Interrupts (SWI) run to completion. Tasks normally run in an infinite loop and within the loop the task tests for a semaphore. A task can preempt itself, e.g: void ProcessTask (void) { while (1) SEM_pend (&taskOneSem, SYS_FOREVER); /* Insert your code here */ }

Putting it all together… void main (void) { /* Put all your setup code here */ return; /*DSP BIOS starts after the return */ } /* Hardware Interrupt */ void timerIsr (void) /* Put your code here */ SWI_post (&SWI_for_algorithm_1); SEM_post (&taskOneSem); /*Software Interrupt */ void algorithm_1 (void) /* Task */ void ProcessTask (void) while (1) SEM_pend (&taskOneSem, SYS_FOREVER); /* Insert your code here */

Putting it all together… void main (void) { /* Put all your setup code here */ return; /*DSP BIOS starts after the return */ } /* Hardware Interrupt */ void timerIsr (void) /* Put your code here */ SWI_post (&SWI_for_algorithm_1); SEM_post (&taskOneSem); /*Software Interrupt */ void algorithm_1 (void) /* Task */ void ProcessTask (void) while (1) SEM_pend (&taskOneSem, SYS_FOREVER); /* Insert your code here */

Putting it all together… See example located in: …\ Chapter 04 - DSP BIOS\Bios_Lab2\bios_lab_2.pjt

Chapter 4 DSP/BIOS Part 3 - Real Time Analysis Tools

Learning Objectives Introduction to the analysis tools. Using the LOG module. Using the STS module. Defining DSP/BIOS objects using the configuration tools. Example.

Introduction Traditionally analysis was performed by halting the processor and examining variables or memory. This traditional method is invasive and does not represent the reality of real-time issues. Real-time analysis is the analysis of data acquired during real-time operation of a system without having to stop or interfere with the target. The API’s and Plug-ins provided with DSP/BIOS enable the programmer to monitor data while the target is running.

Introduction So how can data be monitored without stopping the target? Target-host communications is performed in the background (IDL) thread (e.g. the CPU is performing NOPs or waiting for an interrupt). Data formatting is done by the host and therefore releases the CPU to perform useful tasks. For more details see Chapter 3 of the DSP/BIOS Users Guide (Links\SPRU303.pdf).

DSP/BIOS - API Modules Comm/Synch between threads SEM Semaphores manager MBX Mailboxes manager LCK Resource lock manager Input/Output PIP Data pipe manager HST Host input/output manager SIO Stream I/O manager DEV Device driver interface Memory and Low-level Primitives MEM Memory manager SYS System services manager QUE Queue manager ATM Atomic functions GBL Global setting manager Instrumentation/Real-Time Analysis LOG Message Log manger STS Statistics accumulator manager TRC Trace manager RTDX Real-Time Data Exchange manager Thread Types HWI Hardware interrupt manager SWI Software interrupt manager TSK Multitasking manager IDL Idle function & processing loop manager Clock and Periodic Functions CLK System clock manager PRD Periodic function manger

LOG Module The LOG module contains functions that can be used to capture events in Real-Time while the target program is running. Functions in LOG module: (1) LOG_disable( ): Disable the system log (2) LOG_enable( ): Enable the system log (3) LOG_error( ): Write a user error event to the system log (4) LOG_event( ): Append unformatted message to a message log (5) LOG_message( ): Write a user message to the system log (6) LOG_printf( ): Append a formatted message to a message log (7) LOG_reset( ): Reset the system log

Moving from “printf” to the faster “LOG_printf” How many cycles does the printf() function require? > 34000

Moving from “printf” to the faster “LOG_printf” (1) Include the following headers in the C file: /* #include <stdio.h> NOT required */ #include <std.h> /* this is required by all DSP/BIOS modules */ #include <log.h> /* this is required by the LOG module */ (2) Include the following external reference to the DSP/BIOS object in the C code: extern far LOG_Obj fastprint; /*fastprint is a user chosen name */

Moving from “printf” to the faster “LOG_printf” (3) Create a LOG object using the configuration tool: (a) Open the cdb file, select instrumentation and open the “LOG - Event Log Manager”. (b) Create a new object, call it “fastprint” and change its properties as shown below:

Moving from “printf” to the faster “LOG_printf” (4) Use the following code when using the LOG_printf function: /* #include <stdio.h> NOT required */ #include <std.h> /* this is required by all DSP/BIOS modules */ #include <log.h> /* this is required by the LOG module */ extern far LOG_Obj fastprint; void algorithm_1 (void) { LOG_printf (&fastprint, “Algorithm 1 is running\n”); }

Moving from “printf” to the faster “LOG_printf” (5) To visualise the output of the fastprint log you must open the Message Log window, see below: Note: The complete code can be found in: \Code\Chapter 04 - DSP BIOS\Bios_Lab2\

STS Module The STS module manages objects called statistics accumulators. Each STS object accumulates the following information: Count: The number of values Total: The sum of count values Maximum: The longest value encountered Functions in the STS Module: (1) STS_add( ): Update statistics using provided value (2) STS_delta( ): Update statistics using the difference between the provided value and the set point (3) STS_reset( ): Reset the values stored in the STS object (4) STS_set( ): Save a setpoint value

Using the STS Module (1) Include the following headers in the C file: /* #include <stdio.h> NOT required */ #include <std.h> /* this is required by all DSP/BIOS modules */ /* #include <sts.h> : Created by the tools */ (2) Create an object with the configuration tool: (a) Open the cdb file, select “Instrumentation” and open the “STS - Statistics Object Manager”. (b) Create a new object and call it “mystsObj”.

Using the STS Module (3) You can use the following code to benchmark the printf function: #include <stdio.h> /* Needed for the printf function */ #include <std.h> /* this is required by all DSP/BIOS modules */ #include <sts.h> #include <clk.h> extern far STS_Obj mystsObj; void algorithm_1 (void) { STS_set (&mystsObj, CLK_gethtime()); printf (“Algorithm 1 is running\n”); STS_delta (&mystsObj, CLK_gethtime()); }

Moving from “printf” to the faster “LOG_printf” (4) To visualise the statistics, open the statistics window as shown below: (5) Exercise: Compare the number of cycles the printf and LOG_printf take. Note: The complete code can be found in: \Code\Chapter 04 - DSP BIOS\Bios_Lab3\

Low Instrumentation Overhead LOG, STS and TRC module operations are very fast and execute in constant time, as shown in the following list: LOG_printf and LOG_event: approx 32 cycles STS_add: approx 18 cycles STS_delta: approx 21 cycles TRC_enable and TRC disable: approx 6 cycles Each STS object uses only four words of data memory. This means that the host transfers only four words to upload data from a statistics object.

Chapter 4 DSP/BIOS Part 4 - Real-Time Data Exchange

Learning Objectives Introduction. Example: Send data from the target (DSK6711) to the host (PC).

RTDX: Real-Time Data Exchange PC TMS320 DSP IEEE JTAG EMU H/W R T D X USER CODE Third Party Display CCS User TI 3rd Party MS COM RTDX enables non-obtrusive two-way communication between the host PC and the DSP (during IDL). Since it runs in IDL (by default), it runs lower priority than your real-time code. RTDX is used by DSP/BIOS RTA, but it is also available directly to DSP programmer (useful for testing or if end-equipment is PC resident). Transfer speed limited by: JTAG connection type (parallel, PCI, etc.). DSP activity level.

RTDX: Flow of Data Code Composer Studio controls the flow of data between the host (PC) and the target.

RTDX: Example (1) Target DSK6711 Host In this application a program is written for sending data from the DSK6711 to the host. Code location: \CD ROM 2004\DSP Code 6711 Update\Chapter 04 - DSP BIOS\Bios_Lab3 DSK6711 bios_lab3.pjt Host s1l1.c s1l1.exe

RTDX: Example (2) - Testing the Code (1) Connect and power up the DSK. (2) Envoke CCS and load the program (bios_lab3.out). (3) Enable the RTDX as shown opposite. (4) Run the code. (5) Run the host code “s1l1.cpp.exe” and observe the output. The DSP C code is shown in: \Links\Main3.pdf

DSP/BIOS Feature Summary Features Benefits Easy to use Saves development time Small Footprint (<2Kw) Easily fits in limited memory systems Fast Execution Ideal for real time systems Real-Time Analysis View system parameters while system is executing without breakpoints and without additional overhead - “Test what you fly and fly what you test” Set of Library Functions Use only what you need to minimize footprint Extensible Full featured kernel allows additional OS functions in future

DSP/BIOS Summary At present DSP/BIOS does not support multiprocessors. The “VSPWorks” operating system from WindRiver Systems does support multiprocessing. www.windriver.com

DSP/BIOS Code location: Further Reading: Code\Chapter 04_- DSP BIOS\BIOS_Lab3\bios_lab_3.pjt Further Reading: (1) Use the help provided with the CCS (Help also includes tutorials c:\ti\tutorial\dsk6711). (2) TMS320C6000 DSP/BIOS: User Guide. (3) TMS320C6000 DSP/BIOS: Application Programming Interface (API) SPRU403. (4) Application Report: DSP/BIOS II Timing Benchmarks on the TMS320C6000 DSP SPRA662. (5) Application Report DSP/BIOS II Sizing Guidelines for the TMS320C62x DSP SPRA667.

Chapter 4 DSP/BIOS - End -