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LM3S6965, LM3S2965, LM3S1968 and LM3S8962 Demo
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The demo application has been tested on the following evaluation kits:
- EK-LM3S3768
- EK-LM3S3748
- EK-LM3S6965
- EK-LM3S2965
- EK-LM3S1968
- EK-LM3S8962
The LM3S6965 and LM3S8962 demos creates (amongst other tasks) a simple web server that can be used to both view run time information, and write data to the LED and OLED display on the EVB-LM3S6965/EVB-LM3S8962 evaluation board.
There is a separate documentation page describing how to build and debug the GCC version of this demo using the Eclipse Workbench and OpenOCD. Both of these tools are open source.
The demo uses:
- The FreeRTOS IAR and Keil ARM Cortex-M3 ports.
- Either of: IAR Embedded Workbench for ARM, or the Keil/ARM development tools.
- Adam Dunkels open source uIP embedded TCP/IP stack.
FreeRTOS has made some modifications to the uIP stack since this demo was created. See the Embedded Ethernet Examples List page for more information.
Note for LM3S2965 and LM3S6965 users: The display part number changed on REV C evaluation kit boards. If you are using a REV C board then:
- In the project or makefile, delete the reference to osram128x64x4.c and replace it with rit128x96x4.c. rit128x96x4.c and rit128x96x4.h can be located within the FreeRTOS download as they are already used for other projects.
- In main.c, within the case statement at the top of the vOLEDTask() function, ensure the LM3S2965 and LM3S6965 use the rit128x96x4 driver, as per the other devices initialised within the same case statement.
Note: If this project fails to build then it is likely the version of IAR Embedded Workbench being used is too old. If this is the case, then it is also likely that the project file has been (silently) corrupted and will need to be restored to its original state before it can be built even with an updated IAR version.
IMPORTANT! Notes on using the ARM Cortex-M3 Web Server Demo
Please read all the following points before using this RTOS port.See also the FAQ My application does not run, what could be wrong?
Source Code Organisation
See the Source Code Organization section of the FreeRTOS site for a description of the downloaded files and information on creating a new project.
IAR project files
- The IAR workspace file for the LM3S6965, LM3S2965, LM3S1968 and LM3S8962 FreeRTOS demos is called RTOSDemo.eww and is located in the FreeRTOS/Demo/CORTEX_LM3Sxxxx_IAR_Keil directory.
Keil uVision project files
- The Keil/ARM project file for the LM3S6965, LM3S2965, LM3S1968 and LM3S8962 FreeRTOS demos is called RTOSDemo.uv3 and is also located in the FreeRTOS/Demo/CORTEX_LM3Sxxxx_IAR_Keil directory.
The Demo Application
LM3S6965 / LM3S8962 Demo application setup
The web server will only be included in the build if mainINCLUDE_WEB_SERVER is set to 1 within main.c. Excluding the web server allows the application to be built using the KickStart version of the IAR Embedded Workbench.
Connect the EVB-LM3S6965 or EVB-LM3S8962 development board to a computer running a web browser either directly using a point to point (crossover) cable, or via a hub/router using a standard Ethernet cable. The prototyping board may also allow the use of a standard Ethernet cable when connecting point to point, but I have not tried this configuration.
The IP address used by the demo is set by the constants uipIP_ADDR0 to uipIP_ADDR3 within the file FreeRTOS/Demo/CORTEX_LM3Sxxxx_IAR_Keil/uIP_Task.c. The IP addresses used by the web browser computer and the prototyping board must be compatible. This can be ensured by making the first three octets of both IP addresses identical. For example, if the web browser computer uses IP address 192.168.100.1, then the prototyping board can be given any address in the range 192.168.100.2 to 192.168.100.254 (barring any addresses already present on the network).
The evaluation kits read their MAC address from their internal memory, removing the need for this to be manually configured.
The demo application uses the LED and OLED display built onto the prototyping board so no other hardware setup is required.
The EVB-LM3S6965 / EVB-LM3S8962 is powered, programmed and debugged through the single micro USB connector. You will be prompted to install various USB drivers the first time a USB connection is made between the evaluation board and a PC. The required USB drivers can be obtained from the Luminary Micro CD, or from the Luminary Micro website.
EVB-LM3S2965 / EVB-LM3S1968 demo application setup
Note the comments at the head of this page regarding the selection of the correct display driver.The LM3S2965 and LM3S1968 demos do not require any specific configuration.
Building and executing the demo application
-
Using the IAR development tools
- Set the required IP and MAC address as described above (LM3S6965 and LM3S8962 only).
- Open the FreeRTOS/Demo/CORTEX_LM3Sxxxx_IAR_Keil/RTOSDemo.eww project from within the Embedded Workbench IDE.
- Select 'Rebuild All' from the IDE 'Project' menu. The project should build with no errors or warnings.
- Select 'Debug' from the IDE 'Project' menu. The microcontroller flash memory will be programmed with the demo application, and the debugger will break at the start of the main() function.
The project includes a bitmap that is built into the binary. This increases the binary size and at some optimisation levels will take the build size above the 32K limit of the Embedded Workbench Kickstart edition. If this becomes an issue then the code size can be reduced by excluding the bitmap from the build (by removing the inclusion of the header file bitmap.h within main, and comment out the call to OSRAM128x64x4ImageDraw() within the same file).
-
Using the Keil ARM development tools
- Set the required IP and MAC address as described above (LM3S6965 and LM3S8962 only).
- Open the FreeRTOS/Demo/CORTEX_LM3Sxxxx_IAR_Keil/RTOSDemo.uv2 project from within the uVision IDE.
- Select 'Build Target' from the IDE 'Project' menu. The Keil build does unfortunately generate some warnings when compiling the uIP source.
- Select 'Download' from the 'Flash' menu. The microcontroller flash will be programmed and a debug session commenced.
The demo application is too large to be built using the uVision evaluation software, therefore a licensed copy is required.
The IAR demo was adapted for use with the Keil development tools by Luminary Micro (thanks guys!) and I am unable to test the port myself. The FreeRTOS.org port itself is identical to that used for pre-existing Keil/Cortex-M3 demos.
Functionality
The demo application creates 20 persistent tasks, and periodically dynamically creates and destroys another 2. These tasks consist predominantly of the standard demo application tasks (see the demo application section for details of the individual tasks).The following tasks and tests are created in addition to the standard demo tasks:
- High priority interrupt test [presently for the IAR build only]
A high frequency periodic interrupt is generated using a free running timer to demonstrate the use of the configKERNEL_INTERRUPT_PRIORITY configuration constant. The interrupt service routine measures the number of processor clocks that occur between each interrupt - and in so doing measures the jitter in the interrupt timing. The maximum measured jitter time is latched in the ulMaxJitter variable, and displayed on the OLED display by the 'Check' task as described below. The fast interrupt is configured and handled in the timertest.c source file. This demonstrates how the RTOS kernel can be configured so as to have no impact on higher priority interrupt processing.
The ARM Cortex-M3 core has the ability to hasten the entry into an interrupt service routine (and therefore reduce latency) by up to 8 cycles should a high priority interrupt occur while a lower priority interrupt is already being serviced. The measured jitter time should therefore be no more than 8 clock cycles.
- OLED task
The OLED task is a 'gatekeeper' task. It is the only task that is permitted to access the display directly. Other tasks wishing to write a message to the OLED send the message on a queue to the OLED task instead of accessing the OLED themselves. The OLED task just blocks on the queue waiting for messages - waking and displaying the messages as they arrive.
- Check function - called from the tick hook
This only executes every five seconds. Its main function is to check that all the standard demo tasks are still operational. Should any unexpected behaviour within a demo task be discovered the 'check' function will write an error to the OLED (via the OLED task). If all the demo tasks are executing with their expected behaviour then the check task writes PASS along with the max jitter time to the OLED (again via the OLED task), as described above.
- uIP task (LM3S6965 and LM3S8962 only)
This is the task that handles the uIP stack. All TCP/IP processing is performed in this task.
When executing correctly the demo application will behave as follows:
- The 'check' function will write "PASS" and the jitter time in nanoseconds to the display every 5 seconds.
- The target hardware will serve the web pages described below to a standard web browser (LM3S6965 and LM3S8962 only). To connect to the target:
- Open a web browser on the connected computer.
- Type "HTTP://" followed by the target IP address into the browsers address bar.
Entering the IP address into the web browser
(obviously use the correct IP address for your system)
Served Web Pages (LM3S6965 and LM3S8962 only)
The top of each served page includes a menu containing a link to every other page.
The served RTOS stats page
The RTOS stats page provides run time information on the state of each task within the system - including the stack high water mark (the minimum amount of stack there has been available at any time since the task started executing). The page will reload approximately every two seconds - depending on network load.
This page is transmitted in three sections - the HTML header and menu, the dynamically generated content, then finally the HTML footer. This makes the page relatively fast to load. It could be optimised further by transmitting the entire page in one go.
The continuous reloading can sometimes make navigating away from the RTOS stats page a little tricky.
The served IO page
The IO page provides a simple interface that permits data to be sent to the LED and OLED display on the development board.
The check box permits the state of the user LED to be set and queried. The text box can be used to write a message to the OLED display, but does not query the text currently being display. Changes are sent to the target hardware by clicking the "Update IO" button.
The TCP Stats and Connections pages display run time networking information. Note that these pages transmit each line individually so will not load quickly. This demonstrates how memory usage can be optimised through the use of a small transmit buffer by sacrificing the achieved data throughput.
RTOS Configuration and Usage Details
RTOS port specific configuration
Configuration items specific to these demos are contained in FreeRTOS/Demo/CORTEX_LM3Sxxxx_IAR_Keil/FreeRTOSConfig.h. The constants defined in this file can be edited to suit your application. In particular -- configTICK_RATE_HZ
This sets the frequency of the RTOS tick. The supplied value of 1000Hz is useful for testing the RTOS kernel functionality but is faster than most applications require. Lowering this value will improve efficiency.
- configKERNEL_INTERRUPT_PRIORITY and configMAX_SYSCALL_INTERRUPT_PRIORITY
See the RTOS kernel configuration documentation for full information on these configuration constants.
The lowest priority on a ARM Cortex-M3 core is in fact 255 - however different ARM Cortex-M3 vendors implement a different number of priority bits and supply library functions that expect priorities to be specified in different ways. Use the supplied examples as a reference.
Each port #defines 'BaseType_t' to equal the most efficient data type for that processor. This port defines BaseType_t to be of type long.
Note that vPortEndScheduler() has not been implemented.
Interrupt service routines
In the demo application the vector table remains in flash.Unlike most ports, interrupt service routines that cause a context switch have no special requirements and can be written as per the compiler documentation. The macro portEND_SWITCHING_ISR() can be used to request a context switch from within an ISR.
Note that portEND_SWITCHING_ISR() will leave interrupts enabled.
Switching between the pre-emptive and co-operative RTOS kernels
Set the definition configUSE_PREEMPTION within FreeRTOS/Demo/CORTEX_LM3Sxxxx_IAR_Keil/FreeRTOSConfig.h to 1 to use pre-emption or 0 to use co-operative.Compiler options
As with all the ports, it is essential that the correct compiler options are used. The best way to ensure this is to base your application on the provided demo application files.Memory allocation
Source/Portable/MemMang/heap_2.c is included in the ARM Cortex-M3 demo application project to provide the memory allocation required by the RTOS kernel. Please refer to the Memory Management section of the API documentation for full information.
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