NVIDIA Jetson nano L4T 32.2.1/32.3.1 Kernel modifications

This project aims to describe how to modify the L4T kernel in order to change the Sony IMX219 settings.

How to modify the imx219 driver

There are two important files that need to be modified:

1. The imx219 mode settings - imx219_mode_tbls.h
2. The device tree - tegra210-camera-rbpcv2-imx219.dtsi

The imx219 mode settings - imx219_mode_tbls.h

This file contains the settings of the imx219 camera sensors registry, that can be modified according to the sensors datasheet.

The device tree - tegra210-camera-rbpcv2-imx219.dtsi

The device tree contains camera mode settings needed by the OS.

Important notes

Check the following datasheet for guidance on how to set the different registers in order to configure the image sensor.

1. line blanking needs to be larger than 0xA8
2. line length should be between 0x0D78 and 0x7FF0
3. frame blanking needs to be larger than 0x20
4. frame Length should be between 0x0100 and 0xFFFE
5. The image stream should not exceed the bandwidth of the 2-lane CSI-2 connection. Therefore Width*Height*FPS < 2 * Pixelclock.

How to calculate frame and line length with a given image size and desired FPS?

Frame Length = 2*Pixelclock/(LineLength * FPS)

Our new settings

We managed to implement the following settings:

Sensor Mode	Width x Height	FPS
0	3280x1560	40
5	1640x1232	40

Furthermore, we needed a couple of special frame dimensions, therefore we added theses settings:

Sensor Mode	Width x Height	FPS
1	3280x2464	40
2	1640x780	40
3	1640x780	35
4	1640x780	30

Integration into the yocto build pipeline

We integrated the 0001-added-apic-cameramods.patch into our yocto image build pipeline in order to apply these changes to our build image.

If you are using the build pipeline for the BalenaOS you will need to add the patch into the layers/meta-balena-jetson/recipes-kernel/linux/linux-tegra/ folder and append the layers/meta-balena-jetson/recipes-kernel/linux/linux-tegra_%.bbappend accordingly.

Authors

The NVIDIA CORPORATION is the initial author of imx219_mode_tbls.h and tegra210-camera-rbpcv2-imx219.dtsi. We just modified it a bit to suite our requirements.