Troubleshooting Reinstall

Location of the FEL button on the MOD Duo

Different MOD Duo models (older nand flash model on the left, newer eMMC model on the right

MOD does not boot, or boots into recovery mode automatically

If the main MOD OS kernel becomes unbootable, the MOD will automatically boot into restore mode (used for performing OS updates).
You know the MOD is in restore mode if the inputs and output leds are blue and the display says "plugin USB cable to PC" or "copy file, eject and unplug".

When this happens we need to force a new installation of the MOD OS.
We do this by starting the restore mode with a special "force install" flag.

The method for starting this special mode is:

1. Turn off your MOD
2. Hold the left knob and footswitch down
3. Turn on the MOD (while still holding the knob and footswitch down)
4. Wait 5 seconds and let go of the knob and footswitch
   The MOD is now booting into restore mode, but will allow the installation of any valid MOD release (including the same as already installed or downgrades).
5. Connect the MOD to your PC (if not done yet) and wait for a new mass storage drive to appear
6. Download the latest release from Releases
7. Copy the modduo*.tar file onto the new drive and use your OS option to safely remove the drive
8. Disconnect the USB cable

On some rare cases the MOD might boot again in restore mode after this.
If that happens please start over from step 1.

MOD does not boot at all, not even restore mode

If for some reason your MOD device does not boot at all - not even in forced-restore mode - we need to reinstall the bootloader or perhaps the entire OS inside.
This method is only possible for MOD Duo units.
If you have a MOD Duo X unit that cannot boot normally or in forced-restore mode, please contact support@moddevices.com.

Please note that there are 2 different kinds of MOD Duo units - older ones with nand flash and newer ones with eMMC.
The new unit models have "MOD Duo" written and engraved above the right display.
Knowing which type of unit you have is important as the reinstallation procedure is not the same for each one.

For older models:
You can first try to reinstall the bootloader, which will keep all data intact, but if the issue is somewhere else the MOD will continue to not boot.
This is the best option, if it works. (and applies to your unit, of course)

For all models:
You can also perform a factory reset (which will erase all your data) or keep your data by reinstalling the system over USB.
Note that reinstalling the system over USB only works on Linux at the moment.

Reinstall bootloader

Requirements: MOD Duo unit with nand flash; Linux or macOS, basic command-line knowledge

To begin:

1. Click and hold down the FEL button on the back of the MOD Duo (in tiny hole), while you power it on.
2. Hold it for 2 seconds, then release
3. Connect the MOD Duo to your computer via USB cable
4. Download https://github.com/moddevices/CT_NandBoot/archive/master.zip and extract it
5. Open a terminal and 'cd' to the directory where master.zip was extracted, ie:

cd ~/Downloads/CT_NandBoot-master/

If you're running macOS, run:
./bootfix.osx

If you're running Linux 64bit, run:
./bootfix
(sudo will likely be needed here)

For non-64bit Linux systems, run 'make clean' and 'make' beforehand.

After the command finishes running, just power the MOD off and on again.
If it still doesn't boot after 2 minutes, a factory reset or OS reinstall via USB is needed.

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MOD Duo Factory Reset

Requirements: MOD Duo unit with nand flash; Linux or macOS, basic command-line knowledge
For a factory reset under Windows, see Troubleshooting_Reinstall_via_LiveSuit. (also applies only to MOD Duo units with nand flash)

To begin:

1. Click and hold down the FEL button on the back of the MOD Duo (in tiny hole), while you power it on.
2. Hold it for 2 seconds, then release
3. Connect the MOD Duo to your computer via USB cable
4. Download this file: http://download.moddevices.com/releases/modduo/reset/modduo-latest-reset-image.raw
5. Download https://github.com/moddevices/CT_NandBoot/archive/master.zip and extract it
6. Open a terminal and 'cd' to the directory where master.zip was extracted, ie:

cd ~/Downloads/CT_NandBoot-master/

If you're running macOS, run:
./bootfix.osx -w ~/Downloads/modduo-latest-reset-image.raw
(adjust the path to 'modduo-latest-reset-image.raw' as needed)

If you're running Linux 64bit, run:
./bootfix -w ~/Downloads/modduo-latest-reset-image.raw
(adjust the path to 'modduo-latest-reset-image.raw' as needed, sudo will likely be needed here)

For non-64bit Linux systems, run 'make clean' and 'make' beforehand.

Continuing:

1. Wait until the 'bootfix' process finishes
2. Power off and on the MOD Duo (by replugging the power cable)
3. Wait until its LEDs turn blue, after around 30 seconds. If the LEDs don't light up after one minute, replug the power cable once again
4. Wait until the LEDs turn red, then green. This should take around 10 minutes.

Once the LEDs are green, the MOD Duo has finished its factory reset.
Power it off and on again one last time, and it will be good as new :)

If the LEDs are still blue for too long (actually they go to red and then return to blue) or the display shows the message "copy file, eject and unplug", please execute all this process again starting from the bootfix command.

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Reinstall via USB boot

Requirements: Linux, basic command-line usage

To begin:

1. Click and hold down the FEL button on the back of the MOD Duo (in tiny hole), while you power it on.
2. Hold it for 2 seconds, then release
3. Connect the MOD Duo to your computer via USB cable
4. Download http://download.moddevices.com/releases/modduo/tools/mod-boot-fel-restore.tar.gz and extract it
5. Open a terminal and 'cd' to the directory where mod-boot-fel-restore.zip was extracted, ie:

cd ~/Downloads/mod-boot-fel-restore/

If not you're running 64bit, install sunxi-tools from your Linux distribution, and copy /usr/bin/sunxi-fel to the current directory, overriding the existing file there.

Continuing:

1. Run: ./boot-fel-restore.sh
2. Wait for around 2 minutes, and the MOD Duo will boot into recovery mode.
3. Install a MOD OS release as usual.

Note: You can find all MOD OS software releases in the Releases section.