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ZPUI configuration files

ZPUI config.json


By default, ZeroPhone SD card images and ZPUI installs ship with config.json files that are suitable for usage out-of-the-box. Unless you want to tweak your IO drivers' initialization parameters or need to debug ZPUI in case of hardware trouble, you won't need to edit ZPUI configuration files.

ZPUI depends on a config.json file to initialize the input and output devices. To be exact, it expects a JSON-formatted file in one of the following paths (sorted by order in which ZPUI attempts to load them):

  • /boot/zpui_config.json
  • /boot/pylci_config.json
  • {ZPUI directory}/config.json
  • {ZPUI directory}/config.example.json (a fallback file that you shouldn't edit manually)


The config.json tells ZPUI which output and input hardware it needs to use, so invalid configuration might lock you out of the system. Thus, it's better to make changes in /boot/zpui_config.json - if you screw up and lock yourself out of ZPUI, it's easier to revert the changes since you can do it by just plugging your microSD card in another computer and editing the file. You can also delete (or rename) the file to make ZPUI fallback on a default config file.

ZPUI config format

Here's the default ZPUI config right now:

Here's the config file format:

    "args":[ "value1", "value2", "value3"...]
    "kwargs":{ "key":"value", "key2":"value2"}

Documentation for :doc:`input <input>` and :doc:`output <output>` drivers might have sample config.json sections for each driver. "args" and "kwargs" get passed directly to drivers' __init__ method, so you can read the driver documentation or source to see if there are options you could tweak.

Verifying your changes

You can use jq to verify that you didn't make any JSON formatting mistakes:

jq '.' config.json

If the file is correct, it'll print it back. If there's anything wrong with the JSON formatting, it'll print an error message:

pi@zerophone:~/ZPUI#$ jq '.' config.json parse error: Expected separator between values at line 7, column 10

You might need to install jq beforehand:

sudo apt-get install jq

If you're editing the config.json file externally, you might not have access to the command-line. In that case, you can use an online JSON validator, such as - copy-paste contents of config.json there to see if the syntax is correct.

App-specific configuration files


This section is not yet ready. Sorry for that!

Useful examples

Blacklisting the phone app to get access to UART console

You might find yourself with a cracked screen one day, and needing to connect to your ZeroPhone nevertheless. In the unfortunate case you can't connect it to a wireless network in order to SSH into it (as the interface is inaccessible with a cracked screen), you can use a USB-UART to get to a console accessible on the UART port.

Unfortunately, console on the UART is disabled by default - because UART is also used for the GSM modem. However, you can tell ZPUI to not disable UART by disabling the phone app, and thus enabling the USB-UART debugging. To do that, you need to:

  1. Power down your ZeroPhone - since you can't access the UI, you have no other choice but to shutdown it unsafely by unplugging the battery.
  2. Unplug the MicroSD card and plug it into another computer - both Windows and Linux will work
  3. On the first partition (the boot partition), locate the zpui_config.json file
  4. In that file, add an "app_manager" dictionary (a "collection" in JSON terms)
  5. Add the path to the phone app to a "do_not_load" list inside of it

The resulting file should look like this, as a result:

 "input": ... ,
 "output": ... ,
 "app_manager": {

Now, boot your phone with this config and you should be able to log in over UART!


Since you're editing the config.json file externally, you should make sure it's valid JSON - :ref:`here's a guide for that. <verify_json>`