4.3 KiB
samd20-gcc-blackmagic
A simple GCC setup for Atmel SAM D20 development, intended for use with the blackmagic debug probe.
Prerequisites
GNU Make and the following
standard utilities are required: cat, echo, find, grep,
mkdir, rm, sed and tr. If you're running any sensible desktop
linux then these will already be installed.
You will also need to aquire GNU Tools for ARM Embedded Processors.
On Ubuntu
sudo add-apt-repository ppa:terry.guo/gcc-arm-embedded
sudo apt-get update && sudo apt-get install gcc-arm-none-eabi
Note about gcc-arm-embedded on Ubuntu 14.04 and later
If you are using Ubuntu 14.04 and later, please be careful because there are packages with same name but produced by Debian and inherited by Ubuntu. Simply follow the above 3 steps, you may end up with gcc-arm-none-eabi from Ubuntu. So to install gcc-arm-none-eabi from ARM, steps are:
1). sudo apt-get remove binutils-arm-none-eabi gcc-arm-none-eabi
2). sudo add-apt-repository ppa:terry.guo/gcc-arm-embedded
3). sudo apt-get update
4). sudo apt-get install gcc-arm-none-eabi=4-8-2014q2-0trusty10
Meanwhile we are working with Debian to consolidate and unify this toolchain.
Usage
Project Options
config.mk allows configuation for individual
projects. In particular the PROJECT_NAME and TARGET_CHIP variables
needs to be set.
Compiling
make
Backmagic
Download
Run arm-none-eabi-gdb. If you have set BLACKMAGIC_PATH in
config.mk then gdb will attempt to connect to the
blackmagic debugger. Otherwise you can use the blackmagic command to
connect a /dev/ttyACM<n> device. For example blackmagic 0 will
connect to a blackmagic at /dev/ttyACM0.
To attach to the SAM D20 chip itself you will need to run something like
monitor swdp_scan
attach 1
You can place these commands in a gdbscript-custom file so that in
future they will be run automatically. If monitor swdp_scan fails to
detect an attached SAM D20 device then you may need to upgrade the
firmware on your blackmagic to the latest version.
To download code run
monitor erase_mass
load
Debugging
You can start with the gdb command
run
You might want to use the command set confirm off so that you're not
prompted each time. You might also want to set mem inaccessible-by-default off so that you can look at memory locations
outside of RAM and ROM.
These commands can be automated by placing them in a gdbscript-custom file.
Semihosting
You can build for semihosting by defining the SEMIHOSTING variable
in make. Like this:
make -kB SEMIHOSTING=1
This build will be significantly larger (in terms of RAM and ROM).
For this build, when a debugger is present at startup the
semihost_printf, semihost_puts and semihost_putchar functions
will print to stdio on the host. The Blackmagic Debug Probe supports
this.
Emacs
The command make emacs can be used to quickly launch an instance of
emacs with all the relavent source code loaded.
A TAGS file can be generated with make all or make tags, and
this can be used to automat navigate the source code. See the
emacs manual
for more details.
A Directory Local Variables File .dir-locals.el
exists in the root of the project. This has the following effects
on emacs:
Fixed default-directory
The default directory is fixed as the root of the project wherever you
are within the project. As the makefile needs to be run from the root
of the project, this means that M+x compile will always run the
top-level makefile no matter which file you are editing.
Custom GDB
M+x gdb is set to use arm-none-eabi-gdb rather than the default GDB for your
machine.
Other notes
Wherever possible use Function Attributes and Variable Attrubutes rather than editing the project's linker files.
Sources & Licensing
See LICENSE.md