Compiling FreeRTOS Demo for LPC2106 using GCC on Linux
Introduction
FreeRTOS is an excellent Open Sourced Real Time Operating System, aka RTOS, supporting many different boards. The best way to learn it and start a new project is through their Demos directory, where you pick one that’s more appropriate to your use case. Needless to say, this will be an introductory post/hands-on to FreeRTOS.
One little downside is that a lot of these Demos are for proprietary compilers, or IDEs that no longer exist! Well, I’ve tried to pick a few GCC examples where they had a Makefile so I could work my way out to get a demo building.
In the following sections I’ll be showing you how I did to get the ARM7_LPC2106_GCC demo working on my Linux/Ubuntu machine.
NOTE FreeRTOS has been around for quite some time now, and although it has currently been maintained by Amazon, a lot of its code and demos was written on Windows machines for Windows deployments.
Steps
1. Out-of-the-box attempt
First thing to try was obviously running make out-of-the-box:
$ git clone https://github.com/FreeRTOS/FreeRTOS.git
$ cd FreeRTOS/FreeRTOS/Demo/ARM7_LPC2106_GCC
$ make
arm-elf-gcc -c -Wall -Wextra -Wshadow -Wpointer-arith -Wbad-function-cast -Wcast-align -Wsign-compare -Waggregate-return -Wstrict-prototypes -Wmissing-prototypes -Wmissing-declarations -Wunused -D -D GCC_ARM7 -I. -I../../Source/include -I../Common/include -mcpu=arm7tdmi -T -fomit-frame-pointer -fno-strict-aliasing -fno-dwarf2-cfi-asm ../../Source/portable/GCC/ARM7_LPC2000/portISR.c -o ../../Source/portable/GCC/ARM7_LPC2000/portISR.o
make: arm-elf-gcc: Command not found
Makefile:96: recipe for target '../../Source/portable/GCC/ARM7_LPC2000/portISR.o' failed
make: *** [../../Source/portable/GCC/ARM7_LPC2000/portISR.o] Error 127
As you would certainly expect, that didn’t work at all. Unless you’re into RTOS/Embedded Systems development, you probably won’t have arm-elf-gcc. At first glance, one would run apt sarch arm-elf-gcc and once realized that this returns nothing, one would use his/her Googlefu to try to get it installed.
Let me save some of your sitting hours by letting you know that arm-elf-gcc got incorporated into arm-none-eabi-gcc. This is probably my main motivation to write up this blog post: to let you know that arm-none-eabi-gcc is the thing you should use to compile embedded software, well for ARM boards at least.
Moving on, getting arm-none-eabi-gcc installed is trivial:
$ sudo apt install gcc-arm-none-eabi
# or you can download a newer from ARM's website, then unzip it with `tar xf`
$ wget https://developer.arm.com/-/media/Files/downloads/gnu-rm/10-2020q4/gcc-arm-none-eabi-10-2020-q4-major-x86_64-linux.tar.bz2
2. Tweaking the Makefile
Now that we know which compiler to use, let’s change it in the Demo’s makefile. Locate these lines:
CC=arm-elf-gcc
OBJCOPY=arm-elf-objcopy
ARCH=arm-elf-ar
and replace by these lines:
CC=arm-none-eabi-gcc
OBJCOPY=arm-none-eabi-objcopy
ARCH=arm-none-eabi-ar
It was basically replacing arm-elf- by arm-none-eabi-. Now let’s run it one more time:
$ make
arm-none-eabi-gcc -c -Wall -Wextra -Wshadow -Wpointer-arith -Wbad-function-cast -Wcast-align -Wsign-compare -Waggregate-return -Wstrict-prototypes -Wmissing-prototypes -Wmissing-declarations -Wunused -D -D GCC_ARM7 -I. -I../../Source/include -I../Common/include -mcpu=arm7tdmi -T -fomit-frame-pointer -fno-strict-aliasing -fno-dwarf2-cfi-asm ../../Source/portable/GCC/ARM7_LPC2000/portISR.c -o ../../Source/portable/GCC/ARM7_LPC2000/portISR.o
arm-none-eabi-gcc: error: GCC_ARM7: No such file or directory
Makefile:96: recipe for target '../../Source/portable/GCC/ARM7_LPC2000/portISR.o' failed
make: *** [../../Source/portable/GCC/ARM7_LPC2000/portISR.o] Error 1
Now that we past the compiler not being found error, we’re facing this error: GCC_ARM7: No such file or directory. I don’t know about you, but the first thing I do when I see No such file or directory is start grep’ing so:
$ grep -rn GCC_ARM7
Makefile:38:CFLAGS=$(WARNINGS) -D $(RUN_MODE) -D GCC_ARM7 -I. -I../../Source/include \
Let’s pay attention to this snippet of the Makefile:
28 CC=arm-none-eabi-gcc
29 OBJCOPY=arm-none-eabi-objcopy
30 ARCH=arm-none-eabi-ar
31 CRT0=boot.s
32 WARNINGS=-Wall -Wextra -Wshadow -Wpointer-arith -Wbad-function-cast -Wcast-align -Wsign-compare \
33 -Waggregate-return -Wstrict-prototypes -Wmissing-prototypes -Wmissing-declarations -Wunused
34
35 #
36 # CFLAGS common to both the THUMB and ARM mode builds
37 #
>38 CFLAGS=$(WARNINGS) -D $(RUN_MODE) -D GCC_ARM7 -I. -I../../Source/include \
We can see that, when defining CFLAGS, there are a couple of variables to be expanded: $(WARNINGS) and $(RUN_MODE). The first one is defined in line 32, but there are no definitions for RUN_MODE, thus CFLAGS will be evaluated to ... -D -D GCC_ARM7... that tells the compiler that a macro with name -D should be defined and that GCC_ARM7 is a file to be compiled/linked. As there’s no file like that, gcc will raise the No such file or directory error. We should be finding what $(RUN_MODE) is:
$ grep -rn RUN_MODE
rom_thumb.bat:4:set RUN_MODE=RUN_FROM_ROM
ram_thumb.bat:4:set RUN_MODE=RUN_FROM_RAM
rom_arm.bat:4:set RUN_MODE=RUN_FROM_ROM
ram_arm.bat:4:set RUN_MODE=RUN_FROM_RAM
Makefile:38:CFLAGS=$(WARNINGS) -D $(RUN_MODE) -D GCC_ARM7 -I. -I../../Source/include \
Remember the note in the introduction? Yeah, it’s biting us right here. The file rom_thumb.bat is:
set USE_THUMB_MODE=YES
set DEBUG=
set OPTIM=-O3
set RUN_MODE=RUN_FROM_ROM
set LDSCRIPT=lpc2106-rom.ld
make
This file prepares the environment variables prior to running make. Let’s convert that into a bash script:
export USE_THUMB_MODE=YES
export DEBUG=
export OPTIM=-O3
export RUN_MODE=RUN_FROM_ROM
export LDSCRIPT=lpc2106-rom.ld
make
Now let’s save it to rom_thumb.sh and run it:
$ . rom_thumb.sh
arm-none-eabi-gcc -c -Wall -Wextra -Wshadow -Wpointer-arith -Wbad-function-cast -Wcast-align -Wsign-compare -Waggregate-return -Wstrict-prototypes -Wmissing-prototypes -Wmissing-declarations -Wunused -D RUN_FROM_ROM -D GCC_ARM7 -I. -I../../Source/include -I../Common/include -mcpu=arm7tdmi -Tlpc2106-rom.ld -O3 -fomit-frame-pointer -fno-strict-aliasing -fno-dwarf2-cfi-asm -mthumb-interwork -D THUMB_INTERWORK ../../Source/portable/GCC/ARM7_LPC2000/portISR.c -o ../../Source/portable/GCC/ARM7_LPC2000/portISR.o
arm-none-eabi-gcc -c -Wall -Wextra -Wshadow -Wpointer-arith -Wbad-function-cast -Wcast-align -Wsign-compare -Waggregate-return -Wstrict-prototypes -Wmissing-prototypes -Wmissing-declarations -Wunused -D RUN_FROM_ROM -D GCC_ARM7 -I. -I../../Source/include -I../Common/include -mcpu=arm7tdmi -Tlpc2106-rom.ld -O3 -fomit-frame-pointer -fno-strict-aliasing -fno-dwarf2-cfi-asm -mthumb-interwork -D THUMB_INTERWORK serial/serialISR.c -o serial/serialISR.o
arm-none-eabi-gcc -c -mthumb -Wall -Wextra -Wshadow -Wpointer-arith -Wbad-function-cast -Wcast-align -Wsign-compare -Waggregate-return -Wstrict-prototypes -Wmissing-prototypes -Wmissing-declarations -Wunused -D RUN_FROM_ROM -D GCC_ARM7 -I. -I../../Source/include -I../Common/include -mcpu=arm7tdmi -Tlpc2106-rom.ld -O3 -fomit-frame-pointer -fno-strict-aliasing -fno-dwarf2-cfi-asm -mthumb-interwork -D THUMB_INTERWORK main.c -o main.o
arm-none-eabi-gcc -c -mthumb -Wall -Wextra -Wshadow -Wpointer-arith -Wbad-function-cast -Wcast-align -Wsign-compare -Waggregate-return -Wstrict-prototypes -Wmissing-prototypes -Wmissing-declarations -Wunused -D RUN_FROM_ROM -D GCC_ARM7 -I. -I../../Source/include -I../Common/include -mcpu=arm7tdmi -Tlpc2106-rom.ld -O3 -fomit-frame-pointer -fno-strict-aliasing -fno-dwarf2-cfi-asm -mthumb-interwork -D THUMB_INTERWORK serial/serial.c -o serial/serial.o
arm-none-eabi-gcc -c -mthumb -Wall -Wextra -Wshadow -Wpointer-arith -Wbad-function-cast -Wcast-align -Wsign-compare -Waggregate-return -Wstrict-prototypes -Wmissing-prototypes -Wmissing-declarations -Wunused -D RUN_FROM_ROM -D GCC_ARM7 -I. -I../../Source/include -I../Common/include -mcpu=arm7tdmi -Tlpc2106-rom.ld -O3 -fomit-frame-pointer -fno-strict-aliasing -fno-dwarf2-cfi-asm -mthumb-interwork -D THUMB_INTERWORK ParTest/ParTest.c -o ParTest/ParTest.o
arm-none-eabi-gcc -c -mthumb -Wall -Wextra -Wshadow -Wpointer-arith -Wbad-function-cast -Wcast-align -Wsign-compare -Waggregate-return -Wstrict-prototypes -Wmissing-prototypes -Wmissing-declarations -Wunused -D RUN_FROM_ROM -D GCC_ARM7 -I. -I../../Source/include -I../Common/include -mcpu=arm7tdmi -Tlpc2106-rom.ld -O3 -fomit-frame-pointer -fno-strict-aliasing -fno-dwarf2-cfi-asm -mthumb-interwork -D THUMB_INTERWORK ../Common/Minimal/integer.c -o ../Common/Minimal/integer.o
arm-none-eabi-gcc -c -mthumb -Wall -Wextra -Wshadow -Wpointer-arith -Wbad-function-cast -Wcast-align -Wsign-compare -Waggregate-return -Wstrict-prototypes -Wmissing-prototypes -Wmissing-declarations -Wunused -D RUN_FROM_ROM -D GCC_ARM7 -I. -I../../Source/include -I../Common/include -mcpu=arm7tdmi -Tlpc2106-rom.ld -O3 -fomit-frame-pointer -fno-strict-aliasing -fno-dwarf2-cfi-asm -mthumb-interwork -D THUMB_INTERWORK ../Common/Minimal/flash.c -o ../Common/Minimal/flash.o
arm-none-eabi-gcc -c -mthumb -Wall -Wextra -Wshadow -Wpointer-arith -Wbad-function-cast -Wcast-align -Wsign-compare -Waggregate-return -Wstrict-prototypes -Wmissing-prototypes -Wmissing-declarations -Wunused -D RUN_FROM_ROM -D GCC_ARM7 -I. -I../../Source/include -I../Common/include -mcpu=arm7tdmi -Tlpc2106-rom.ld -O3 -fomit-frame-pointer -fno-strict-aliasing -fno-dwarf2-cfi-asm -mthumb-interwork -D THUMB_INTERWORK ../Common/Minimal/PollQ.c -o ../Common/Minimal/PollQ.o
arm-none-eabi-gcc -c -mthumb -Wall -Wextra -Wshadow -Wpointer-arith -Wbad-function-cast -Wcast-align -Wsign-compare -Waggregate-return -Wstrict-prototypes -Wmissing-prototypes -Wmissing-declarations -Wunused -D RUN_FROM_ROM -D GCC_ARM7 -I. -I../../Source/include -I../Common/include -mcpu=arm7tdmi -Tlpc2106-rom.ld -O3 -fomit-frame-pointer -fno-strict-aliasing -fno-dwarf2-cfi-asm -mthumb-interwork -D THUMB_INTERWORK ../Common/Minimal/comtest.c -o ../Common/Minimal/comtest.o
arm-none-eabi-gcc -c -mthumb -Wall -Wextra -Wshadow -Wpointer-arith -Wbad-function-cast -Wcast-align -Wsign-compare -Waggregate-return -Wstrict-prototypes -Wmissing-prototypes -Wmissing-declarations -Wunused -D RUN_FROM_ROM -D GCC_ARM7 -I. -I../../Source/include -I../Common/include -mcpu=arm7tdmi -Tlpc2106-rom.ld -O3 -fomit-frame-pointer -fno-strict-aliasing -fno-dwarf2-cfi-asm -mthumb-interwork -D THUMB_INTERWORK ../Common/Minimal/flop.c -o ../Common/Minimal/flop.o
arm-none-eabi-gcc -c -mthumb -Wall -Wextra -Wshadow -Wpointer-arith -Wbad-function-cast -Wcast-align -Wsign-compare -Waggregate-return -Wstrict-prototypes -Wmissing-prototypes -Wmissing-declarations -Wunused -D RUN_FROM_ROM -D GCC_ARM7 -I. -I../../Source/include -I../Common/include -mcpu=arm7tdmi -Tlpc2106-rom.ld -O3 -fomit-frame-pointer -fno-strict-aliasing -fno-dwarf2-cfi-asm -mthumb-interwork -D THUMB_INTERWORK ../Common/Minimal/semtest.c -o ../Common/Minimal/semtest.o
arm-none-eabi-gcc -c -mthumb -Wall -Wextra -Wshadow -Wpointer-arith -Wbad-function-cast -Wcast-align -Wsign-compare -Waggregate-return -Wstrict-prototypes -Wmissing-prototypes -Wmissing-declarations -Wunused -D RUN_FROM_ROM -D GCC_ARM7 -I. -I../../Source/include -I../Common/include -mcpu=arm7tdmi -Tlpc2106-rom.ld -O3 -fomit-frame-pointer -fno-strict-aliasing -fno-dwarf2-cfi-asm -mthumb-interwork -D THUMB_INTERWORK ../Common/Minimal/dynamic.c -o ../Common/Minimal/dynamic.o
arm-none-eabi-gcc -c -mthumb -Wall -Wextra -Wshadow -Wpointer-arith -Wbad-function-cast -Wcast-align -Wsign-compare -Waggregate-return -Wstrict-prototypes -Wmissing-prototypes -Wmissing-declarations -Wunused -D RUN_FROM_ROM -D GCC_ARM7 -I. -I../../Source/include -I../Common/include -mcpu=arm7tdmi -Tlpc2106-rom.ld -O3 -fomit-frame-pointer -fno-strict-aliasing -fno-dwarf2-cfi-asm -mthumb-interwork -D THUMB_INTERWORK ../Common/Minimal/BlockQ.c -o ../Common/Minimal/BlockQ.o
arm-none-eabi-gcc -c -mthumb -Wall -Wextra -Wshadow -Wpointer-arith -Wbad-function-cast -Wcast-align -Wsign-compare -Waggregate-return -Wstrict-prototypes -Wmissing-prototypes -Wmissing-declarations -Wunused -D RUN_FROM_ROM -D GCC_ARM7 -I. -I../../Source/include -I../Common/include -mcpu=arm7tdmi -Tlpc2106-rom.ld -O3 -fomit-frame-pointer -fno-strict-aliasing -fno-dwarf2-cfi-asm -mthumb-interwork -D THUMB_INTERWORK ../../Source/tasks.c -o ../../Source/tasks.o
arm-none-eabi-gcc -c -mthumb -Wall -Wextra -Wshadow -Wpointer-arith -Wbad-function-cast -Wcast-align -Wsign-compare -Waggregate-return -Wstrict-prototypes -Wmissing-prototypes -Wmissing-declarations -Wunused -D RUN_FROM_ROM -D GCC_ARM7 -I. -I../../Source/include -I../Common/include -mcpu=arm7tdmi -Tlpc2106-rom.ld -O3 -fomit-frame-pointer -fno-strict-aliasing -fno-dwarf2-cfi-asm -mthumb-interwork -D THUMB_INTERWORK ../../Source/queue.c -o ../../Source/queue.o
arm-none-eabi-gcc -c -mthumb -Wall -Wextra -Wshadow -Wpointer-arith -Wbad-function-cast -Wcast-align -Wsign-compare -Waggregate-return -Wstrict-prototypes -Wmissing-prototypes -Wmissing-declarations -Wunused -D RUN_FROM_ROM -D GCC_ARM7 -I. -I../../Source/include -I../Common/include -mcpu=arm7tdmi -Tlpc2106-rom.ld -O3 -fomit-frame-pointer -fno-strict-aliasing -fno-dwarf2-cfi-asm -mthumb-interwork -D THUMB_INTERWORK ../../Source/list.c -o ../../Source/list.o
arm-none-eabi-gcc -c -mthumb -Wall -Wextra -Wshadow -Wpointer-arith -Wbad-function-cast -Wcast-align -Wsign-compare -Waggregate-return -Wstrict-prototypes -Wmissing-prototypes -Wmissing-declarations -Wunused -D RUN_FROM_ROM -D GCC_ARM7 -I. -I../../Source/include -I../Common/include -mcpu=arm7tdmi -Tlpc2106-rom.ld -O3 -fomit-frame-pointer -fno-strict-aliasing -fno-dwarf2-cfi-asm -mthumb-interwork -D THUMB_INTERWORK ../../Source/portable/MemMang/heap_2.c -o ../../Source/portable/MemMang/heap_2.o
arm-none-eabi-gcc -c -mthumb -Wall -Wextra -Wshadow -Wpointer-arith -Wbad-function-cast -Wcast-align -Wsign-compare -Waggregate-return -Wstrict-prototypes -Wmissing-prototypes -Wmissing-declarations -Wunused -D RUN_FROM_ROM -D GCC_ARM7 -I. -I../../Source/include -I../Common/include -mcpu=arm7tdmi -Tlpc2106-rom.ld -O3 -fomit-frame-pointer -fno-strict-aliasing -fno-dwarf2-cfi-asm -mthumb-interwork -D THUMB_INTERWORK ../../Source/portable/GCC/ARM7_LPC2000/port.c -o ../../Source/portable/GCC/ARM7_LPC2000/port.o
arm-none-eabi-gcc -Wall -Wextra -Wshadow -Wpointer-arith -Wbad-function-cast -Wcast-align -Wsign-compare -Waggregate-return -Wstrict-prototypes -Wmissing-prototypes -Wmissing-declarations -Wunused -D RUN_FROM_ROM -D GCC_ARM7 -I. -I../../Source/include -I../Common/include -mcpu=arm7tdmi -Tlpc2106-rom.ld -O3 -fomit-frame-pointer -fno-strict-aliasing -fno-dwarf2-cfi-asm -mthumb-interwork -D THUMB_INTERWORK ../../Source/portable/GCC/ARM7_LPC2000/portISR.o serial/serialISR.o main.o serial/serial.o ParTest/ParTest.o ../Common/Minimal/integer.o ../Common/Minimal/flash.o ../Common/Minimal/PollQ.o ../Common/Minimal/comtest.o ../Common/Minimal/flop.o ../Common/Minimal/semtest.o ../Common/Minimal/dynamic.o ../Common/Minimal/BlockQ.o ../../Source/tasks.o ../../Source/queue.o ../../Source/list.o ../../Source/portable/MemMang/heap_2.o ../../Source/portable/GCC/ARM7_LPC2000/port.o -nostartfiles boot.s -Xlinker -ortosdemo.elf -Xlinker -M -Xlinker -Map=rtosdemo.map
arm-none-eabi-objcopy rtosdemo.elf -O ihex rtosdemo.hex
And we got it working!
3. Is this correct?
Honestly, I don’t know. The post goal is just to get you up and running with basic changes that might need to be done to get some of FreeRTOS Demos working. I have an ESP32 Devkit laying around my desk, but I couldn’t find any Demos for it yet. The plan is to write another blog post about that in the future. Stay tuned and sorry if I disappointed you by not testing the binary :)
Thanks for your time and attention.
Chaws