Compiling Kernel For Android ARM With Ender-3 Pro ch341 Driver (Galaxy S3 i9300)

Kernel Driver Support to Connect to Ender

For any rom, if you want to connect it to Ender 3, you need "ch341" driver added/activated in the kernel or you need a custom implementation of it (look for octo4a program). You could understand it by connecting the phone with a USB OTG cable to your printer and execute command "ls /dev | grep tty". If  there is "ttyusb" or "ttyacm" , it means that kernel has the driver. If kernel does not have the driver you have two options: 

1. You need to compile a kernel with driver support. Also keep in mind that kernel needs to support "loopback" functionality to host a virtual linux system and accept/direct connections to that virtual linux over its loopback.
2. You can install octo4a, which installs custom a ch34x driver. and you need to mount the serial pipe of the octo4a (you can check that part from: https://github.com/d4rk50ul1/klipper-on-android) 

• Terminal Emulator (you need to give root priviliges)
  

Compiling Kernel for ARM (Galaxy S3 i9300)

If you do not want to bother with all compiling, just download the boot.img that i compiled. It is for  CrDroid LineageOS rom install Galaxy s3 i9300s. 

I will be telling the procedure for Samsung galaxy s3 but it should be generally applicable to any ARM (not ARM64) android phone:

• Twrp installation on galaxy s3:
• Crdroid rom: which is pre-rooted and Lineageos based and Android 7.1.2. 

So i searched for Lineage os based 7.x kernels on github and found a one with "ch341" driver already included in its folders. 

• Kernel Github Link
• Kernel Github Link - Supported Devices

Good part is that this kernel supports many phones, loopback and usb audio/dock station mode. You need a linux environment to compile kernel (might be possible on windows too). First you need to download the kernel and a toolchain (Google) to compile it. 

We need programs/files listed below: 

• AIK KITCHEN folder (to split and merge new kernel into boot.img file) 
• arm-eabi folder (google toolchain to compile kernel) 
• Kernel folder (new kernel source code)
• boot.img file (we will replace the kernel in this original image file taken from firm zip file) 

1. Installing prerequisites 

sudo apt-get install libncurses5 libncurses5-dev
sudo apt-get install make
sudo apt-get install git

2. Install google toolchain

cd /home/ercin
git clone https://android.googlesource.com/platform/prebuilts/gcc/linux-x86/arm/arm-eabi-4.8 

3. Download Android image kitchen  and extract it to a folder. (/home/ercin/Downloads/AIK-Linux)

4. Download CrDroid rom and extract boot.img file

At the end you will have a Download folder  with folders and images like below: 

5. Edit kernel configuration file to include ch341 driver  (you need to find the defconfig file for your phone type, which is generally under /arch/arm/configs folder inside kernel folder)

6. Compile New Kernel

export ARCH=arm
export SUBARCH=arm
export CROSS_COMPILE=/home/ercin/Downloads/arm-eabi-4.8/arm-eabi-
cd /home/ercin/Downloads/elite-boeffla-kernel-lineage14.1-i9300-master/
make clean
make mrproper
make lineageos_i9300_defconfig
make -j$(nproc --all)

7.Now you have the kernel with name Zimage under arch/arm/boot folder: 

/home/ercin/downloads/elite-boeffla-kernel-lineage14.1-i9300-master/arch/arm/boot/Zimage

8. Unpack boot.img (taken from crdroid zip file) and change old kernel with newly compiled one. 

cd /home/ercin/Downloads/AIK-Linux/
./unpackimg.sh /home/ercin/Downloads/boot.img 
cd /home/ercin/Downloads/AIK-Linux/split_img/
rm boot.img-zImage
cp  /home/ercin/downloads/elite-boeffla-kernel-lineage14.1-i9300-master/arch/arm/boot/Zimage boot.img-zImage
cd /home/ercin/Downloads/AIK-Linux/
./repackimg.sh 

Now you have image-new.img file under folder /home/ercin/Downloads/AIK-Linux

8. Install image-new.img file to phone boot section using TWRP