Modifications and modules guide
Me and madmonkey spent many hours to create modules system for hakchi/hakchi2 (it's compatible) to let people create, share and download various modules for NES Classic Mini with custom skins, music, emulators, etc. It's time to write some guide to let you create your own modifications! I'll show you some examples below. So if you can't understand a word, please read until examples section.
At first time, we did not have feedback from NES Mini over USB connection, so we used UART cable which was soldered inside NES Mini:
So it was very difficult to create some mods without this cable and soldering skills. But I discovered method which allows to access NES Mini's file system and command line using only USB connection. I called it "clovershell" and it's built in hakchi2 since version 2.14. So you don't need any extra hardware to explore NES Mini. Yes, UART cable still recommended but everything can be done without soldering now, you need only software.
All required software is built in hakchi2 since version 2.16, check "Tools" menu:
But there are some extra tools recommended:
- clovershell client - my tool which allows to execute shell commands on NES Mini and push/pull files via USB.
- Telnet client - software to access NES Mini's command line, bundled with Windows "telnet.exe" is fine but putty is recommended.
- FTP client - software to transfer files, bundled with Windows will work but it's better to use something like FileZilla Client or FAR. FAR is my favorite one.
- It's good idea to install also MSYS - a collection of GNU utilities for Windows.
NES Classic Mini is just a tiny computer with ARM processor and Linux. So basic Linux knowledge will be very handy if you want to create some advanced scripts. It's not so difficult, really.
There are directories of NES Classic Mini after system boot by default (without hakchi installed):
The first thing you need to understand is mounting. In Linux devices and directories can be mounted on other directories. Internal flash memory devided into several partitions.
- ~20MB in size, factory pre-programmed, read-only, contains all system data and games, mounted on / (root)
- ~384MB in size, writable, contains all user settings and save-states, mounted on /var/lib
So you can't rewrite any original data but there are much free space for additional data. Also there are RAM disks:
- Mounted on /var
- Mounted on /run Data on this disks are stored in RAM only and erased every time you turn NES Mini off.
Note that the directories are nested inside each other. It means that:
- / - points to root of read-only, factory pre-programmed partition
- /etc - points to "/etc" folder on read-only, factory pre-programmed partition
- /usr/share/games - points to "/usr/share/games" folder on read-only, factory pre-programmed partition
- /tmp - points to other writable RAM disk
- /var/lib - points to writable partition on NAND flash memory
It can be difficult to understand for Windows users but you'll get it.
So, we can't edit any internal files or add some games to /usr/share/games directory, it's read-only file system. But actually we don't need to do it. We can create any files/directories into "**/var/lib" and overmount them over the original files/directories. So when hakchi during installation doing the following:
- Creates directory "/var/lib/hakchi" to store all additional data, it remains after system shutdown
- Creates directory "/var/lib/hakchi/rootfs" to store all files/directories which need to replace
- Creates directory "/var/lib/hakchi/rootfs/usr/share/games/nes/kachikachi"
- Copies all games from "/usr/share/games/nes/kachikachi" to "/var/lib/hakchi/rootfs/usr/share/games/nes/kachikachi"
- Overmounts "/var/lib/hakchi/rootfs/usr/share/games/nes/kachikachi" over "/usr/share/games/nes/kachikachi", so it's writable now
He is doing the same with "/etc" and "/bin", after this hakchi installs additional configs and scripts there. So we can write to "/etc" and "/bin" while original files will be untouched. It's very important. You can delete all data you want but your NES Mini will not be bricked since original files are safe.
So, why we need to install custom kernel? Actually it has only one important modification: When NES Mini boots up it executes "/etc/preinit" (or "/var/lib/hakchi/rootfs/etc/preinit", it's the same file) script on the very early boot stage. This script, in turn, executes files from "/etc/preinit.d" directory. So we can store our overmounting scripts there.
Lets sum everything up. To edit any file/directory on read-only file system you need:
- Create copy of this file/directory into "/var/lib/hakchi/rootfs/your_directory"
- Create script file into /etc/preinit.d" which overmounts "/var/lib/hakchi/rootfs/your_directory" on "/your_directory"
- After reboot edit this file/directory without any problems
I'll try to visualize it:
It's better to understand on practice, so keep reading.
There are some useful functions defined into ""/etc/preinit.d/b0010_functions" script. You can use them into your preinit scripts since "b0010_functions" executed before.
- overmount <file/directory> - overmounts file directory, example: "overmount /usr/share/games/nes/kachikachi" overmounts "/var/lib/hakchi/usr/share/games/nes/kachikachi" on "overmount /usr/share/games/nes/kachikachi" making it writable, it can be used with two arguments too to set custom destination mount point
- copy <path_a> <path_b> - copies file/directory using rsync (recommended to use instead of cp)
- copy_mask <path_a> <path_b> - same as copy but can be used with mask, this function is unsafe, avoid spaces in filenames!
Please read ""/etc/preinit.d/b0010_functions" to understand other functions. Also there are useful pre-defined variables:
- modname=hakchi
- modpath=/var/lib/hakchi (but really it's "/newroot/var/lib/hakchi" on pre-init stage)
- installpath=$mountpoint/var/lib/$modname
- firmwarepath=$installpath/firmware
- rootfs=$installpath/rootfs
- preinit=$rootfs/etc/preinit
- preinitpath=$preinit.d
- gamepath=/usr/share/games/nes/kachikachi
- temppath=/tmp
Modules for hakchi/hakchi2 should be distributed as files with ".hmod" extension. Actually it's just renamed .tar.gz archive, so you can rename any .hmod file, unpack and inspect how it's made. There are several such files into "mods\hmods" directory of hakchi2 (it's a pre-installed mods: controller hack, font hack and clovershell daemon). Also hakchi2 can install unpacked hmods if it's a directory, you can find one such example into "user_mods\music_hack.hmod", this mod replaces menu music (with silence by default but you can change wav file with your favorite music track).
So, what .hmod archive can contain:
- First of all, any files which you need to install on NES Mini, it's recommended keep directory structure
- Optional "install" script
- Optional "uninstall script
- Optional "readme.txt" file with some description/info
What happens during module installation:
- If "install" file exists, it will be executed, it can contain any hakchi functions and variables from above
- If "install" returned non-zero value or it not exists, all files will be copied to "/var/lib/hakchi/rootfs" directory (excluding "install", "uninstall" and readme files)
- If "uninstall" file exists it will be stored into "/var/lib/hakchi/hmod" directory
- If "uninstall" file does not exists, it will be created automatically based on installed files list
What happens during module uninstallation:
- Corresponding "uninstall" file will be executed and removed
Lets start with something very simple. Do you want to customize your NES Mini and create your own theme for it? So lets locate it inside NES Classic Mini. At first, enable FTP server:
And login into it using "127.0.0.1" as address, 1021 as port "root" as login and "clover" as password.
It's easy to realize that all images stored into /usr/share/clover-ui/resources/sprites/nes.png file:
So we can download this file and edit using your favorite graphic editor without any problems! But... we can't rewrite this file, it's stored on read-only file system inside NES Mini. But we can write files inside "/var/lib" directory, so lets save our modified file as /var/lib/hakchi/rootfs/usr/share/clover-ui/resources/sprites/nes.png:
It saved successfully but it will not replace original /usr/share/clover-ui/resources/sprites/nes.png on it's own. We need to create pre-init script to overmount this file on early boot stage. Actually it's very easy to do. All pre-init scripts are stored into "/etc/preinit.d" (actually it's "/var/lib/hakchi/rootfs/etc/preinit.d" but it's overmounted onto "/etc/preinit.d", so who cares) directory. We need to create new file here:
File must be named as pxxxx_name where "xxxx" is a hexadecimal digits and "name" is any text. You can choose any valid name but keep in mind that all pre-init scripts will be executed in alphabetical order. It can be important in some cases.
So lets create "/etc/preinit.d/p8032_skin" file with only one line:
overmount /usr/share/clover-ui/resources/sprites/nes.png
That's all. Just reboot your NES Classic Mini and you will see your custom theme:
But what if you want to share your mod? Open "user_mods" directory inside hakchi2's directory and create folder named "my_skin.hmod" here. You can choose any name but it must be with ".hmod" on the end. Then just copy all files that you created inside NES Mini into this "my_skin.hmod" folder. You must keep all directory structure under "/var/lib/hakchi/rootfs", so it must contain "\usr\share\clover-ui\resources\sprites\nes.png" and "etc\preinit.d\p8032_skin" files.
Also it's good idea to create some "readme.txt" file inside "my_skin.hmod" folder with some mod description. We can also create "install" and "uninstall" files but this is not required for such simple mod, hakchi will create install and uninstall scenarios automatically.
You should be able to install/uninstall this mod using hakchi2 now:
But you should distribute your mods not as directories but as single ".hmod" files which are actually tar.gz archives. So lets create this archive file using tar util from MSYS collection:
So we have "awesome_skin.hmod" file now which can be easily shared with other users. All they need to do is just drag-and-drop this file on hakchi2's window. And it's still compatible with original madmonkey's hakchi. But actually I'm not sure that it's totally legal to share skin files when they are based on original NES Mini's files.
You can use the same way to edit any other NES Mini's files: music, sounds, text, etc.
Many people asked me to remove thumbnails at the bottom of the screen. This feature was introduced in early versions but removed later. So lets create mod to do it!
Let's check files of NES Mini... There is "/usr/share/clover-ui/resources/prefab/sys_game_thumbnail.scn" file with some JSON data. And there is "enabled" boolean variable!
You already know what to do from previous example:
- Download "sys_game_thumbnail.scn" file to PC
- Edit it, change "enabled" from "true" to "false"
- Upload it to NES Mini as "/var/lib/hakchi/rootfs/usr/share/clover-ui/resources/prefab/sys_game_thumbnail.scn"
- Create pre-init script to overmount this file
But we will not do it. We will use other method. Open "user_mods" directory inside hakchi2's directory, create folder named "remove_thumbnails.hmod" here and create file "install" inside it. It's our installation script which will be executed during mod installation process. Lets write it:
# Lines started with "#" are ignored and can be used as comments
# Next line defines "scnfile" variable with path to "sys_game_thumbnail.scn" file
scnfile=/usr/share/clover-ui/resources/prefab/sys_game_thumbnail.scn
# This line defines "preinitfile" variable with pre-init file name
preinitfile=p81a8_hide_thumnbnails
# "restore" is hakchi function which copies original file to corresponding path in /var/lib/hakchi/rootfs
restore $scnfile
# sed is GNU util to modify file, this command replaces "enabled:true" to "enabled:false"
# Please note that we need to edit $rootfs$scnfile (writable file), not a just $scnfile (original read-only) file
sed -i -e 's/"enabled":true/"enabled":false/g' $rootfs$scnfile
# Create pre-init script and echo "overmount" command to it
echo "overmount $scnfile" > $preinitpath/$preinitfile
# We should return 1 to prevent execution of automatic installer
return 1
That's all. But don't forget to create "uninstall" script too:
# All we need is to delete created files, original file is safe and will be used again after reboot
scnfile=/usr/share/clover-ui/resources/prefab/sys_game_thumbnail.scn
preinitfile=p81a8_hide_thumnbnails
rm -f $preinitfile
rm -f $rootfs$scnfile
Lets install our mod...
Oops...
Thumbnails are removed but cursor is still there. It's part of skin, so we can just make it's transparent, but it will conflict with previous skin mod. It's very important to prevent mods conflicts.
There is other config file - "/usr/share/clover-ui/resources/sprites/nes.json", and it contains coordinates and properties for every sprite on the screen:
So lets change our "install" script to replace sprite properties:
# Lines started with "#" are ignored and can be used as comments
# Next line defines "scnfile" variable with path to "sys_game_thumbnail.scn" file
scnfile=/usr/share/clover-ui/resources/prefab/sys_game_thumbnail.scn
# Same with "nes.json" file
nesjson=/usr/share/clover-ui/resources/sprites/nes.json
# This line defines "preinitfile" variable with pre-init file name
preinitfile=p81a8_hide_thumnbnails
# "restore" is hakchi function which copies original file to corresponding path in /var/lib/hakchi/rootfs
restore $scnfile
restore $nesjson
# sed is GNU util to modify file, this command replaces "enabled:true" to "enabled:false"
# Please note that we need to edit $rootfs$scnfile (writable file), not a just $scnfile (original read-only) file
sed -i -e 's/"enabled":true/"enabled":false/g' $rootfs$scnfile
# Same with nes.json file, most simple way is to replace coordinates sprite coords with zeros
sed -i -e 's/\[93,861,12,8\]/\[0,0,0,0\]/g' $rootfs$nesjson
sed -i -e 's/\[93,871,12,8\]/\[0,0,0,0\]/g' $rootfs$nesjson
sed -i -e 's/\[107,861,12,8\]/\[0,0,0,0\]/g' $rootfs$nesjson
# Create pre-init script and echo "overmount" command to it
echo "overmount $scnfile" > $preinitpath/$preinitfile
echo "overmount $nesjson" >> $preinitpath/$preinitfile
# We should return 1 to prevent execution of automatic installer
return 1
Done! No more thumbnails and cursor at the bottom of the screen!
I'll bundle this mod with hakchi v2.17, so you can check and edit it on your own.
Are you ready to rock and create something really complicated? My child is playing too much, and I want to limit his access to NES Classic Mini somehow. So I desired to create password protection mod.
One of the coolest things in Linux is a ability to do near everything using only shell scripts. Another one cool thing is "everything is file" concept, so we can access devices as usual files. First of all, we need to enable Telnet server and connect to NES Mini's shell using Telnet client.
Lets find controller pseudo-file.
The "/dev/input/by-path/platform-twi.1-event-joystick" file is just what we need. It outputs data on every event from controller. But this is binary data, so we need "hexdump" util to convert this data into human readable hexademical format.
This is what I get after pressing "Up", "Up", "Down", "Down". There is too much data just for four button presses! It outputs 32 bytes on every button press and 32 bytes on every button release. But you don't need to be character from Matrix movie to find some pattern:
So button code is in 11th and 12th bytes of every packet. Lets trim them out... Enter command:
while [ true ]; do buttons=$(cat /dev/input/by-path/platform-twi.1-event-joystick | hexdump -v -e '1/1 "%02x"' -n 32); echo -n "${buttons:20:4} "; done
And press some buttons...
Wow, there are our button codes! But we also need to ask user for password somehow. I draw three simple images with "1280x720" resolution (it's screen resolution of NES Mini, e.g. 720p):
But we need to convert them into RAW format since there is no any software to show images on NES Mini. Of course, we can write this software, compile it for ARM processor and install on NES Mini but this is too much just for static images. There are many tools to convert images into RAW format, NES Mini uses "BGRA" byte order. RAW files are huge, so it's better to use gzip to compress them. I stored this files as "password.raw.gz", "password_fail.raw.gz" and "password_ok.raw.gz" into "/etc/" directory. So I can draw them on screen using simple command:
gunzip -c /etc/password.raw.gz > /dev/fb0
This command loads "/etc/password.raw.gz" file and writes unzipped data to "/dev/fb0" pseudo-file which is frame-buffer representation.
Finally, lets write password protection scrip.! I'll store it as "/etc/init.d/S810password" which is executed after "S79clovercon" (controller driver) but before "S81clover-mcp" (main GUI). Please note that line endings MUST be UNIX-style (\n instead of \r\n). Also please note that you can't brick your NES Mini but any error can cause boot loop or any other fail during startup. Don't panic, you can remove broken script using "uninstall" process. So, lets go!
#!/bin/sh
# Some constants
# Controller pseudo-file
clovercon=/dev/input/by-path/platform-twi.1-event-joystick
# Password pattern - it's Konami Code :)
password="c202 c202 c302 c302 c002 c102 c002 c102 3101 3001 3b01"
# Max tries
max_tries=30
# Init scripts are executed with "start" argument when system boots and with "stop" argument during shutdown
# So we need to check that it's boot state, not shutdown
[ -z "$1" ] || [ "$1" == "start" ] || exit 0
# Drawing "ENTER PASSWORD" image
gunzip -c /etc/password.raw.gz > /dev/fb0
# Endless loop
while [ true ]; do
# Wait while pseudo-file doesn't exists (controller is not connected or is not initialized yet)
while [ ! -e $clovercon ]; do usleep 100; done
# Reading buttons
buttons=$(cat $clovercon | hexdump -v -e '1/1 "%02x"' -n 32)
buttons=${buttons:20:4}
# Appending pressed button to "str" variable
str="$str $buttons"
# If "str" variable is longer than password string, cut it
# So we get only last presses
[ "${#str}" -gt "${#password}" ] && str="${str:$((${#str}-${#password})):${#password}}"
# Is password correct?
if [ "$str" == "$password" ]; then
# Display "OK" image
gunzip -c /etc/password_ok.raw.gz > /dev/fb0
# Exit and continue system loading
exit 0
fi
# Password is not correct yet, decrease tries counter
max_tries=$(($max_tries-1))
# Is it zero?
if [ "$max_tries" == "0" ]; then
# Display "ACCESS DENIED" image
gunzip -c /etc/password_fail.raw.gz > /dev/fb0
# Wait for three seconds
sleep 3
# Shutdown system
poweroff
fi
done
That's it! NES Mini will ask for password during boot now. I'll bundle this mod with hakchi v2.17 too.
Just in case you don't know - it's easy to transform your NES Classic Mini into Famicom Mini and vice-versa. All you need is to upload firmware file into "/var/lib/hakchi/firmware" folder (create it). Of course I can't share firmware files due to copyright violations but you can easily find them on torrents:
- dp-hvc-release-v1.0.5-0-g2f04d11.hsqs - to transform NES Mini into Famicom Mini
- dp-nes-release-v1.0.2-0-g99e37e1.hsqs - to transform Famicom Mini into NES Mini
Just upload one of those files using FTP and reboot your console. Don't forget also to change "Console type" in hakchi2, select foreign "Original 30 games" and sync if you want to get foreign games too, not only foreign GUI.
But what if you want to use Famicom Mini with NES Mini's language of interface? Actually it's very simple to do. You need:
- Overmount "/usr/share/clover-ui/resources/scripts/system.lua" file using this file from NES Mini, it will enable language selection dialog and icon
- Overmount the whole "/usr/share/clover-ui/resources/strings" folder, it contains strings for all languages (btw, you can edit them too if you want)
- Overmount "/usr/share/clover-ui/resources/fonts/hvc" folder with "/usr/share/clover-ui/resources/fonts/nes" folder extracted from NES Classic Mini.
Sorry, I can't share those files. But you can extract them on your own. Let's take this as your homework :)