The main purpose of integrating QP/C with conventional RTOSes is to enable you to incorporate various communication stacks (TCP/IP, USB, CAN, etc.) as well as other middleware, which requires the ability to **block** the task code.
You do **not** need to use a third-party RTOS just to achieve preemptive multitasking with QP/C. The framework contains a selection of built-in real-time kernels, such as the cooperative @ref qv "QV kernel", the preemptive non-blocking @ref qk "QK kernel", and the preemptive, dual-mode, blocking @ref qxk "QXK kernel". Specifically, the QXK kernel has been designed specifically for mixing event-driven active objects with traditional **blocking code**, such as commercial middleware (TCP/IP stacks, UDP stacks, embedded file systems, etc.) or legacy software.
The @ref dpp "DPP example" for embOS on STM32F4-Discovery board is located directory <span class="img folder">examples/embos/arm-cm/dpp_stm32f429-discovery</span>.
The sub-directory <span class="img folder">iar</span> contains the workspace and project file that you can open in IAR EWARM IDE.
After you load the DPP example into the STM32F4-Discovery board, the application should start blinking the 4 on-board LEDs. You can press the User button (blue) to PAUSE the philosophers for as long as the button is depressed. The philosophers resume dining when you release the User button. (In the PAUSED state the Table active object stops granting permissions to eat, so eventually all philosophers end in the "hungry" state.)
The DPP example for embOS on STM32F4-Discovery board provides the "Spy" build configuration, which outputs the QS (Quantum Spy) software tracing data through USART2. To get the data out of the board, you need to connect the TTL/RS232 converter as follows:
/*! @page freertos_start-stop_nucleo-h743zi Start-Stop on NUCLEO-H743ZI
@image html bd_NUCLEO-H743ZI.jpg NUCLEO-H743ZI
Start-Stop example for NUCLEO-H743ZI MCU (Cortex-M7) demonstrates staring and stopping active objects multiple times
during the runtime, as opposed to starting AOs only at the beginning.
The code for the example is generated automatically by the [QM Model-Based Design tool](https://www.state-machine.com/qm/) (QM version 4.5.0 or higher).
The start-stop application consists of two AOs:
- the Launcher AO is started at the beginning and its job is to periodically (re)start another AO
- the Worker AO is NOT started at the beginning, but instead it is instantiated and started by the Launcher AO.
The actual visible work is performed by the Worker AO, which blinks the yellow LED (LD1) on the NUCLEO-H743ZI board. After blinking the LED five times, the Worker AO publishes turns the blue LED (LD2), publishes the DONE event and stops itself (by calling QP::QActive::stop() on itself).
The Launcher AO subscribes to the DONE event. Upon reception of this event, The Launcher AO gives the Worker a bit of time (at least one clock tick) to cleanly terminate and then it explicitly destroys the Worker. The Worker destructor turns the blue LED (LD2) off.
Next the Launcher instantiates the Worker AO by means of the placement new operator and then it starts it again to repeat the cycle, which goes no forever.
@remarks
Because this application is intended for embedded real-time systems, it does not use the dynamic memory (heap). Instead it uses statically allocated memory (static mode of FreeRTOS) as well as **placement-new** and explicit destructor call.
It is possible to use the standard **new** and **delete** operators with the standard heap, or some customized memory allocation (overloaded new/delete). This goes beyond the scope of this example.
**Supported Toolchains** @n
This example contains sub-directories for building it with various toolchains. The following toolchains are supported:
This example demonstrates the [QP/Spy software tracing](https://www.state-machine.com/qtools/qpspy.html) in the **Spy build configuration**. The QP/Spy uses the virtual COM port provided by the NUCLEO-H743ZI board. To see the QP/Spy output, you need to launch the qspy host utility, as follows (Windows command prompt):
@verbatim
qspy -u -c COM4
@endverbatim
where COM4 is the particular virtual serial port registered by your NUCLEO board. You need to adjust the COM port number for your machine.
**Programming the NUCLEO Board** @n
The NUCLEO boards appear as a USB-flash drive in the file system. Programming of the board is done by simply copying the binary into
thy flash drive letter.
For example, assuming that the NUCLEO board appears as drive E:, you program it with the following command:
@verbatim
copy dbg\start-stop.bin E:
@endverbatim
**Demonstrated Features** @n
- multiple active objects (Launcher and Worker)
- instantiating, starting and stopping active objects multiple times
- [QP/Spy software tracing](https://www.state-machine.com/qtools/qpspy.html) using the virtual COM-port
- bi-directional [QP/Spy](https://www.state-machine.com/qtools/qs.html#qs_rx) (sending commands to the target)
The @ref dpp "DPP example" for ThreadX on STM32F4-Discovery board is located directory <span class="img folder">examples/threadx/arm-cm/dpp_stm32f429-discovery</span>.
The sub-directory <span class="img folder">iar</span> contains the workspace and project file that you can open in IAR EWARM IDE.
After you load the DPP example into the STM32F4-Discovery board, the application should start blinking the 4 on-board LEDs. You can press the User button (blue) to PAUSE the philosophers for as long as the button is depressed. The philosophers resume dining when you release the User button. (In the PAUSED state the Table active object stops granting permissions to eat, so eventually all philosophers end in the "hungry" state.)
The DPP example for ThreadX on STM32F4-Discovery board provides the "Spy" build configuration, which outputs the QS (Quantum Spy) software tracing data through USART2. To get the data out of the board, you need to connect the TTL/RS232 converter as follows:
