Lidar Mapping (PoC) »

Notes for Jetson Nano

Tips, hints, and tricks when working on Jetson Nano

Last update: 2022-06-29

Table of Content

Check log#

Get system log:

dmesg

Log file:

cat /var/log/syslog

List of built-in modules#

cat /lib/modules/$(uname -r)/modules.builtin | grep spi

kernel/drivers/media/spi/imx204.ko
kernel/drivers/mtd/devices/qspi_mtd.ko
kernel/drivers/mtd/spi-nor/spi-nor.ko
kernel/drivers/spi/spi-tegra114.ko
kernel/drivers/spi/spi-tegra124-slave.ko
kernel/drivers/spi/spi-tegra210-qspi.ko

Build kernel and modules#

This is a method to build Kernel image and modules directly on the Jetson board.

Firstly, clone build scripts:

git clone https://github.com/jetsonhacks/jetson-linux-build.git && \
cd jetson-linux-build

Download kernel source. The script will automatically detect the kernel version.

./getKernelSources.sh

Kernel modules can be configured using KConfig Menu:

./editConfig.sh

Example of reviewing SPI driver for Tegra114.

Browse to Device Drivers → SPI support and check detail of NVIDIA Tegra114 SPI Controller by pressing H:

.config - Linux/arm64 4.9.140 Kernel Configuration
> Device Drivers > SPI support ------------
------NVIDIA Tegra114 SPI Controller-------
│ CONFIG_SPI_TEGRA114:                    │
│                                         │
│ Symbol: SPI_TEGRA114 [=y]               │
│ Type  : tristate                        │
│ Prompt: NVIDIA Tegra114 SPI Controller  │
│   Location:                             │
│     -> Device Drivers                   │
│       -> SPI support (SPI [=y])         │
│   Defined at drivers/spi/Kconfig:626    │
│   Depends on:...

This driver uses the symbol SPI_TEGRA114 which is defined at drivers/spi/Kconfig:626.

Check the Makefile in /usr/src/kernel/$(uname -r)/drivers/spi/Makefile:
```
obj-$(CONFIG_SPI_MASTER)        += spi.o
obj-$(CONFIG_SPI_SPIDEV)        += spidev.o
obj-$(CONFIG_SPI_LOOPBACK_TEST) += spi-loopback-test.o
obj-$(CONFIG_SPI_TEGRA114)      += spi-tegra114.o
```
Trace to .config file in the kernel folder /usr/src/kernel/$(uname -r). Read more at Makefile.
```
CONFIG_SPI=y
CONFIG_SPI_MASTER=y
CONFIG_SPI_SPIDEV=m
CONFIG_SPI_TEGRA114=y
```
The CONFIG_SPI_TEGRA114=y means spi_tegra114 is a platform driver, not a module, therefore it needs to rebuild kernel image to include change in that driver.
Edit the source code or apply a patch
Rebuild kernel image
```
./makeKernel.sh
```
It takes about an hour at the first time.
Replace BOOT image at line LINUX /boot/Image by editing the boot file:
```
cat /boot/extlinux/extlinux.conf
```
Should back up the kernel image first.

Reboot!

Find in file#

grep --include=\*.{c,h} -rnw '.' -e "SPI_MODE_1"

Check shared libraries#

ld -lrf24 --verbose

Wrap C lib to C++ lib#

Add wrapper to the header file

#ifdef __cplusplus
extern "C" {
#endif

... header content here...

#ifdef __cplusplus
}
#endif

Device Tree Compile#

Decompile:

dtc -I dtb -O dts <input.dtb> -o <output.dts>

Edit .dts file, and then recompile:

dtc -I dts -O dtb <input.dts> -o <output.dtb>

Replace FDT file at line FDT /boot/xxx.dtb by editing the boot file cat /boot/extlinux/extlinux.conf. Should back up the kernel image first.

Fix USB Partition#

USB with wrong partition table can not be read. Erase the entire partition table is needed.

sudo dd if=/dev/zero of=/dev/sda bs=512 count=1

Then use fdisk to create GPT partition table and add new partition.

sudo fdisk /dev/sdx

The format the partition:

sudo mkfs.ext4 /dev/sdxy

Visual Studio Code#

Visual Studio Code is far better than Sublime Text. Here is a method to install it automatically:

wget -qO- https://packages.microsoft.com/keys/microsoft.asc \
    | gpg --dearmor \
    > packages.microsoft.gpg \
&& \
sudo install -o root -g root -m 644 \
    packages.microsoft.gpg \
    /etc/apt/trusted.gpg.d/ \
&& \
rm -f packages.microsoft.gpg \
&& \
sudo sh -c \
    'echo "\
        deb [signed-by=/etc/apt/trusted.gpg.d/packages.microsoft.gpg] \
        https://packages.microsoft.com/repos/code stable main\
    " \
    > /etc/apt/sources.list.d/vscode.list' \
&& \
sudo apt install -y apt-transport-https \
&& \
sudo apt update \
&& \
sudo apt install -y code

Plugins:

Sublime Text key map
C/C++

Configs:

.vscode\c_cpp_properties.json

{
    "configurations": [
        {
            "browse": {
                "databaseFilename": "",
                "limitSymbolsToIncludedHeaders": true
            },
            "includePath": [
                "${workspaceFolder}/devel/include",
                "/opt/ros/melodic/include/**",
                "/usr/include/**",
                "${workspaceFolder}/**"
            ],
            "name": "ROS",
            "configurationProvider": "ms-vscode.cmake-tools"
        }
    ],
    "version": 4
}

Submodule in Git#

Add a new module:

git submodule add <remote_url>

Initialize submodule:

git submodule init

Download submodule after initializing:

git submodule update

Remove a module:

git submodule deinit <submodule_name>

Clone and download all submodules:

git clone --recursive <repo_url>