commit 92cdbeda088e8ae76116d0a8d0b63e1a8fc0fcbf
Author: MikoĊaj Lenczewski <mikolaj@lenczewski.org>
Date: Thu, 21 May 2026 01:28:00 +0100
Initial commit
Diffstat:
17 files changed, 308 insertions(+), 0 deletions(-)
diff --git a/.gitignore b/.gitignore
@@ -0,0 +1,2 @@
+bin/
+obj/
diff --git a/LICENSE b/LICENSE
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diff --git a/README b/README
@@ -0,0 +1,87 @@
+gp24
+==============================================================================
+Example project on how to lay out a small, multi-language embedded codebase for
+controlling a greenpower racecar.
+
+gp24: Motivation
+==============================================================================
+A greenpower car consists of the following critical systems:
+- Batteries : We need to store energy to do anything
+- Motors : We need to move the car
+- Controls : We need to accept inputs from the driver (i.e. throttle)
+- Heads-Up Display : We need to show things to the driver (i.e. battery level)
+
+Optionally, it may also contain the following systems:
+- Telemetry : We might want to log debug and status information when running
+
+Fundamentally, greenpower is about optimising your battery usage. You want to
+minimise the work the motors have to do to accelerate you to speed and keep
+you there, and want to maximise the time the motors can keep you at speed for.
+
+To do that, we need to minimise the amount of work done by the control system
+beyond that which is absolutely necessary. That means minimal processing on any
+inputs taken from the driver, minimal processing on any inputs taken from the
+car itself, and a minimal GUI to display only the neccessary information.
+
+Alongside this goal of minimising work, however, is the need to know how the
+car is performing. Both for debugging failures, as well as helping with future
+development, we need to at least log the state of the car at regular intervals
+to an SD card (or other removable storage). If the power budget allows, there
+is also the option of using remote telemetry from the car to the pit, to store
+telemetry on the receiving device.
+
+gp24: Architecture
+==============================================================================
+We want to have the ability to target a variety of devices, to potentially
+do initial testing and prototyping on a more ergonomic development board, and
+then refine the result to run on a lower-power board when integrated into the
+final car. To achieve this goal, we need to abstract away from concrete
+microcontrollers as much as possible. To help with this, we write in mainly
+C/C++, with platform-specific assembly helpers and a hardware abstraction
+layer where necessary.
+
+Thus, for each platform that the project targets and builds for, we have
+the following:
+
+```
+<target>.lds - platform-specific linker script
+<target>/plat.S - platform-specific assembly code, used by HAL
+<target>/hal.c - platform-specific hardware abstraction layer
+<target>/*.c - additional platform-specific C source files
+<target>/*.h - additional platform-specific C header files
+```
+
+This HAL is then used by the platform-independent portion of the code,
+located under `src/*.{cpp,hpp,h}`. This is where the bulk of the code exists,
+including the main loop, the graphics code, and the telemetry code.
+
+The top-level source file to start from is `src/gp24.cpp`, which includes all
+further source files in a "unity build" fashion. This approach allows precise
+control over the placement of any static variables, control over the order of
+definition of symbols, avoids multiple rounds of header file parsing, as well
+as cleaning up and simplifying the build script.
+
+Any third-party dependencies, such as header-only libraries, or hardware
+definition headers (e.g. defining memory-mapped addresses), live under the
+`dep/` directory. These may be platform-dependent, and if so their use must
+be guarded by the relevant `#ifdef` guards.
+
+Any documentation is kept under `docs/`.
+
+gp24: Building
+==============================================================================
+To build the project, there exists `build.sh`. When ran without any arguments,
+it will build for the default platform. To specify what platform to build for,
+it is necessary to pass a commandline argument, as follows:
+
+```
+$ ./build.sh <platform> # see `build.sh` for available values for <platform>
+```
+
+Building the project results in an elf file, `bin/gp24.elf`. This is useful
+when debugging, to get symbol information to your debugger of choice. For
+flashing onto the target platform, however, there are also `bin/gp24.bin` and
+`bin/gp24.hex` that are generated. A symbol map is also generated for debugging
+purposes, and can be found at `bin/gp24.map`.
+
+To clean the project, there exists `clean.sh`.
diff --git a/atmega2560.lds b/atmega2560.lds
diff --git a/atmega2560/hal.c b/atmega2560/hal.c
diff --git a/atmega2560/plat.S b/atmega2560/plat.S
@@ -0,0 +1,4 @@
+.globl _start
+
+_start:
+ rjmp .
diff --git a/build.sh b/build.sh
@@ -0,0 +1,81 @@
+#!/bin/sh
+
+TARGET="${1:-atmega2560}"
+
+# toolchain
+AS="clang"
+CC="clang"
+CXX="clang++"
+LD="ld.lld"
+
+OBJCOPY="llvm-objcopy"
+
+# toolchain flags
+WARNINGS="-Wall -Wextra ${WERROR:+-Werror} -Wno-unused-parameter"
+FLAGS="-ffreestanding -fno-builtin"
+
+# generic language flags
+ASFLAGS="-g3"
+CFLAGS="-std=c11 -O0 -g3"
+CXXFLAGS="-std=c++11 -O0 -g3"
+
+CPPFLAGS="-Idep"
+LDFLAGS="-nostdlib"
+
+# target-specific toolchain flags
+# --
+# see: clang -target avr-none --print-supported-cpus
+# see: clang -target arm-none-eabi --print-supported-cpus
+# see: clang -target arm-none-eabi --print-supported-extensions
+#
+# see: https://gcc.gnu.org/onlinedocs/gcc/AVR-Options.html
+# see: https://gcc.gnu.org/onlinedocs/gcc/ARM-Options.html
+case $TARGET in
+ atmega2560) # arduino mega
+ TRIPLE="avr-none"
+ TARGET_FLAGS="-mmcu=atmega2560"
+ ;;
+
+ stm32-m3) # stm nucleo-64
+ TRIPLE="arm-none-eabi"
+ TARGET_FLAGS="-mcpu=cortex-m3 -march=armv7-m"
+ ;;
+
+ stm32-m4) # stm32 nucleo-144
+ TRIPLE="arm-none-eabi"
+ TARGET_FLAGS="-mcpu=cortex-m4 -march=armv7e-m+fp"
+ ;;
+
+ *)
+ echo "Unsupported target: $TARGET, must be one of: "
+ echo "\tatmega2560 stm32-m3 stm32-m4"
+ exit 1
+ ;;
+esac
+
+# target-specific language flags
+ARCH_ASFLAGS="-target $TRIPLE $TARGET_FLAGS $ASFLAGS $FLAGS"
+ARCH_CFLAGS="-target $TRIPLE $TARGET_FLAGS $CFLAGS $FLAGS"
+ARCH_CXXFLAGS="-target $TRIPLE $TARGET_FLAGS $CXXFLAGS $FLAGS"
+
+ARCH_CPPFLAGS="$CPPFLAGS"
+ARCH_LDFLAGS="-T $TARGET.lds $LDFLAGS"
+
+set -ex
+
+mkdir -p bin obj
+
+# build target-specific asm platform code and HAL implementation
+$AS $ARCH_ASFLAGS $ARCH_CPPFLAGS -o obj/plat.o -c $TARGET/plat.S -I$TARGET
+$CC $ARCH_CFLAGS $ARCH_CPPFLAGS -o obj/hal.o -c $TARGET/hal.c -I$TARGET
+
+# build target-independent code
+$CXX $ARCH_CXXFLAGS $ARCH_CPPFLAGS -o obj/gp24.o -c src/gp24.cpp
+
+# link together asm helpers, HAL, and main code
+$LD $ARCH_LDFLAGS --Map=bin/gp24.map --print-memory-usage \
+ obj/plat.o obj/hal.o obj/gp24.o -o bin/gp24.elf
+
+# prepare binary for flashing to target
+$OBJCOPY -S -O binary bin/gp24.elf bin/gp24.bin
+$OBJCOPY -S -O ihex bin/gp24.elf bin/gp24.hex
diff --git a/clean.sh b/clean.sh
@@ -0,0 +1,5 @@
+#!/bin/sh
+
+set -ex
+
+rm -rf bin obj
diff --git a/dep/.keep b/dep/.keep
diff --git a/docs/.keep b/docs/.keep
diff --git a/src/gp24.cpp b/src/gp24.cpp
diff --git a/stm32-m3.lds b/stm32-m3.lds
diff --git a/stm32-m3/hal.c b/stm32-m3/hal.c
diff --git a/stm32-m3/plat.S b/stm32-m3/plat.S
@@ -0,0 +1,4 @@
+.globl _start
+
+_start:
+ b .
diff --git a/stm32-m4.lds b/stm32-m4.lds
diff --git a/stm32-m4/hal.c b/stm32-m4/hal.c
diff --git a/stm32-m4/plat.S b/stm32-m4/plat.S
@@ -0,0 +1,4 @@
+.globl _start
+
+_start:
+ b .
