112 lines
3.6 KiB
Markdown
112 lines
3.6 KiB
Markdown
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# FreeRTOS Demo for the NEORV32 Processor
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This example shows how to run [FreeRTOS](https://www.freertos.org/) on the NEORV32 processor. It features the default
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"blinky_demo" and the more sophisticated "full_demo" demo applications. See the comments in `main.c` and the according
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source files for more information.
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The chip-specific extensions folder (`chip_specific_extensions/neorv32`) should be in `$(FREERTOS_HOME)/Source/portable/GCC/RISC-V/chip_specific_extensions`,
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but is placed in this source directory for simplicity.
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**:information_source: Tested with FreeRTOS version V10.4.4+**
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## Requirements
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* Hardware
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* DMEM/IMEM requirements depend on the actual application (for example: 16kB DMEM and 16kB IMEM for "blinky_demo")
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* peripherals: MTIME (machine timer), UART0, GPIO
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* CPU ISA extensions: `Zicsr`
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* Software
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* NEORV32 software framework
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* RISC-V gcc
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* FreeRTOS
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* application-specific configuration of `FreeRTOSConfig.h` (especially `configCPU_CLOCK_HZ`)
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* application-specific configuration of the NEORV32 linker script when using non-default IMEM or DMEM configurations (size!)
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## Instructions
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Download FreeRTOS from the [official GitHub repository](https://github.com/FreeRTOS/FreeRTOS) or from the its official homepage.
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$ git clone https://github.com/FreeRTOS/FreeRTOS.git
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Open the makefile from this example folder and configure the `FREERTOS_HOME` variable to point to your FreeRTOS home folder.
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FREERTOS_HOME ?= /mnt/n/Projects/FreeRTOSv10.4.1
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Compile the NEORV32 executable. Do not forget the `RUN_FREERTOS_DEMO` switch.
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$ make USER_FLAGS+=-DRUN_FREERTOS_DEMO clean_all exe
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Note: The *.c sources and the FreeRTOS-specific part of the makefile have (include) guards that test if `RUN_FREERTOS_DEMO` is defined.
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This has no practical usage for the user - it is just a work-around for the NEORV32 CI environment.
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Upload the executable (`neorv32_exe.bin`) to the processor via the bootloader and execute it.
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```
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CMD:> u
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Awaiting neorv32_exe.bin... OK
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CMD:> e
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Booting...
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FreeRTOS V10.4.4+ on NEORV32 Demo
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Blink
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Blink
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Blink
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Blink
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```
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## FreeRTOS Plus
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To automatically add source and include files from FreeRTOS plus extensions add one (or more) of the following arguments when invoking `make`:
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* FreeRTOS-Plus-CLI: `USER_FLAGS+=-FREERTOS_PLUS_CLI`
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* FreeRTOS-Plus-TCP: `USER_FLAGS+=-FREERTOS_PLUS_TCP`
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Example:
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$ make USER_FLAGS+=-DRUN_FREERTOS_DEMO USER_FLAGS+=-FREERTOS_PLUS_TCP clean_all exe
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## NEORV32-Specific Interrupts and Exceptions
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The `main.c` file provides two "trampolines" for NEORV32-specific interrupts/exceptions:
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```c
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/* Handle NEORV32-specific interrupts */
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void freertos_risc_v_application_interrupt_handler(void) {
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// acknowledge/clear ALL pending interrupt sources
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neorv32_cpu_csr_write(CSR_MIP, 0);
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// debug output
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neorv32_uart0_printf("\n<NEORV32-IRQ> mcause = 0x%x </NEORV32-IRQ>\n", neorv32_cpu_csr_read(CSR_MCAUSE));
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}
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/* Handle NEORV32-specific exceptions */
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void freertos_risc_v_application_exception_handler(void) {
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// debug output
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neorv32_uart0_printf("\n<NEORV32-EXC> mcause = 0x%x </NEORV32-EXC>\n", neorv32_cpu_csr_read(CSR_MCAUSE));
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}
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```
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This functions can be used to call specific handlers based on the value from the `mcause` CSR, which indicates
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the actual cause of the interrupt or exception (for example FIRQ channel or illegal instruction).
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## Notes
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The onfiguration of the FreeRTOS home folder (via `FREERTOS_HOME`) is corrupted if the compiler shows the following error:
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```
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main.c:36:10: fatal error: FreeRTOS.h: No such file or directory
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36 | #include <FreeRTOS.h>
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| ^~~~~~~~~~~~
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compilation terminated.
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make: *** [makefile:203: main.c.o] Error 1
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```
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