NuttX support for Gemstone is still in the development phase. It is not possible to use all peripherals on the board
such as I2C, SPI, PWM, CAN Bus.
nsh configuration has been created in the
boards/arm/am67/t3-gem-o1 directory. With this configuration, NuttX can be run on the R5F cores on our board, which
are suitable for real-time processing.
1. Compilation
To compile NuttX, the system must have several prerequisites installed. Additionally, we need a cross‑compiler that is
compatible with ARM Cortex‑R5F cores. The gcc-arm-none-eabi toolchain is the standard solution that fulfills this
requirement.
On Ubuntu/Debian systems, you can install the dependencies and toolchain using the package manager:
sudo apt update
sudo apt install \
bison flex gettext texinfo libncurses5-dev libncursesw5-dev xxd \
git gperf automake libtool pkg-config build-essential gperf genromfs \
libgmp-dev libmpc-dev libmpfr-dev libisl-dev binutils-dev libelf-dev \
libexpat1-dev gcc-multilib g++-multilib picocom u-boot-tools util-linux \
kconfig-frontends gcc-arm-none-eabi
arm-none-eabi-gcc --version command.
1.2. Downloading Source Codes
The NuttX ecosystem consists of two main repositories: the core operating system and the application framework. To
download the versions customized for the Gemstone board, follow these steps:
# Clone the main NuttX repository
git clone https://github.com/t3gemstone/nuttx.git
# Clone NuttX applications as the 'apps' folder
git clone https://github.com/t3gemstone/nuttx-apps.git apps
# Change to your main working directory
cd nuttx
apps folder contains the
applications and services that will run on the operating system.
1.3. Applying the Default Configuration
NuttX uses pre-prepared configurations for different hardware platforms. Let’s start by applying the t3-gem-o1:nsh
configuration for our Gemstone board:
./tools/configure.sh -l t3-gem-o1:nsh
1.5. Compiling the Project
After the configuration is complete, we can compile NuttX:
This command performs a parallel compilation using all the CPU cores available on your system. The compilation results
in an ELF file named nuttx. This file contains the operating system image to be loaded onto the R5F core.
1.6. Customizing the Configuration
Sometimes you may need to make changes to the default configuration. NuttX uses the menuconfig tool, similar to the
Linux kernel. Through this graphical interface, you can activate drivers, change memory settings, or add new features.
Your changes are stored in the .config file.
To make your changes permanent and able to be added to the version control system, use the savedefconfig command. This
command saves only the configurations that differ from the default settings, thus preventing the configuration file from
becoming unnecessarily large. You can copy the resulting defconfig file to the nsh default configuration under the
boards/arm/am67/t3-gem-o1/configs directory or create a new configuration with a different name.
1.7. Cleanup Operations
During development, you may sometimes need a fresh start. NuttX offers two levels of cleanup commands:
# Only cleans object files and binaries
make clean
# Cleans all build files and the configuration
make distclean
make clean command deletes the files resulting from the compilation but preserves the configuration. make distclean completely reverts the project to its initial state, in which case you need to perform the configuration
process again.
2. Running
While the NuttX operating system runs on the R5F cores, the Linux operating system also runs on the A53 cores. Code can
be loaded onto the R5F cores using the remoteproc mechanism present in the Linux operating system and U-Boot.
Program files to be loaded onto the cores via remoteproc must be copied to the /lib/firmware directory with predefined
names. At system startup, the remoteproc mechanism will automatically load the programs onto the relevant cores. Follow
the steps below to run NuttX using remoteproc.
- Copy the
nuttx file resulting from the compilation to the /lib/firmware directory with the name j722s-main-r5f0_0-fw.
- Reboot the board.
- You can access NuttShell by connecting a USB-to-TTL device to the UART-MAIN1’s GPIO-14 (TX) and GPIO-15 (RX) pins on the 40-pin HAT.
- From the opened
nsh console, you can run the program named blink and observe the user LEDs on the board blinking.
3. Debug
3.1. Enabling Debug Features
NuttX is configured in release mode by default, which produces a small-sized ELF file that is optimized but contains no
debug information. To perform step-by-step debugging during development, you will need to switch to debug mode.
Open the menuconfig tool and follow this path: Build Setup → Debug Options → Enable Debug Features. Also, enable
the Generate Debug Symbols option. These settings cause the compiler to embed debug information into the ELF, allowing
the debugger to debug at the source code level.
3.2. CCS IDE Integration
Texas Instruments Code Composer Studio (CCS) is a development environment specifically optimized for the AM67A SoC
family. To integrate your NuttX project into CCS, open the IDE and use File → Import → C/C++ → Existing Code as Makefile Project. Select the nuttx folder as the project directory.
3.3. Loading the Program onto the Core
To start the debug process via the CCS IDE, first create a Target Configuration by selecting the Debug Probe model you
will use (e.g., Texas Instruments XDS200) and the J722S_TDA4VEN_TDA4AEN_AM67 board. Then, start the Target
Configuration and connect to the AM67A SoC.
After the debugger connection is established, select the Main R5F core and use Run → Load → Load Program to select
the nuttx ELF file. This operation loads the NuttX operating system into the R5F core’s memory.
Once the program is loaded, you can set breakpoints, watch variables, and step through the code. You can examine
critical components of NuttX, such as its task scheduler and interrupt handlers, in detail this way.
