The Picture Transfer Protocol (PTP) facilitates remote operations on a camera connected computer. Typical operations are uploading/downloading photos and remote captures.

Most cameras support some basic operations over PTP, but often only in a limited fashion. For example, downloading of files can be limited to just JPEG files.

The PTP extension for CHDK discussed in this article does not alter the standard operations but adds new CHDK-specific operations instead. This is due to the complexity involved in altering or complete overwriting the standard operations. It also means that special tools are required to access this new functionality.

If you want simple control over the camera without USB a protocol connection (for example, using a micro-controller or RC equipment) see USB Remote. Note the USB remote option must be disabled to use the PTP Extension.

The CHDK extension was first added to the CHDK trunk in changeset 957, and has been enabled for all cameras since changeset 1116

Related forum thread: CHDK PTP interface

Functionality Edit

An overview of the functionality available through the PTP interface is described below. The specific functionality and usage depends on which client application you use. The canonical reference to the CHDK PTP protocol is core/ptp.h in the CHDK source tree.

File transferEdit

Files can be uploaded to and downloaded from any part of the file system.

Script executionEdit

The PTP interface allows execution of lua scripts sent over PTP. In general, any scripting function available to normal CHDK scripts can be executed remotely. See CHDK Scripting Cross Reference Page for a list of CHDK script functions. There are some additional functions specific to PTP, described in Lua/PTP Scripting.

Some of the features available using Lua scripts include

  • Switch to and from record mode
  • Switch recording modes, e.g. Av, Tv, Video
  • Adjust exposure parameters, focus, zoom etc.
  • Shoot pictures or video
  • Manipulate Canon menus and settings with simulated key presses
  • List, create and delete files and directories
  • Return values from script, send and receive arbitrary messages between the camera and PC
  • Shutdown or reboot the camera

Remote displayEdit

CHDK 1.1 add support streaming the contents of the camera LCD display over PTP. (revision 1921 and later)

Remote shootingEdit

CHDK 1.2 added support for saving images directly over USB, without saving on the SD card. This is supported for raw and DNG on all cameras, and for jpeg on some cameras. For raw and DNGs capturing a subset of rows from the raw framebuffer is also supported.

Debugging featuresEdit

  • Read and write camera memory
  • call arbitrary camera functions

LibUSB Driver for Windows Edit

All the client applications below require libusb-win32 driver on Windows.

Installing LibUSB using ZadigEdit

Zadig is recommended, especially on Windows 8 and later which restrict the use of unsigned drivers. To install libusb using this tool:

  • Download the appropriate file for your OS from
  • Connect the camera via USB
    • If you have never connected the camera before, wait for Windows to install its default driver
  • Run zadig_2.2.exe
  • Click Options > List All Devices
  • Select in the dropdown (usually Canon Digital Camera)
    • If you have multiple Canon cameras, make sure only one is connected and powered on
    • You can edit the name to allow identifying the driver later
    • Be sure you have the camera selected. If you select the wrong device, the device you selected may become unusable until you remove the driver. The existing driver should be something like WUDFRd on Win7 or WUDFWpdMtp on Win10. The USB ID should be 04A9 for a Canon camera, and the second part will be the PID of your camera.
  • Select libusb-win32 by clicking the up/down arrows in the Driver box
  • Click Replace Driver
  • Restart the camera before attempting to access it with a CHDK client. There is no need to restart your PC.

Related forum post [1]

Removing the LibUSB driverEdit

To remove the driver installed by Zadig or the INF wizard

  • Open device manager
  • Select View - Show Hidden Devices
  • Find the driver under libusb-win32 Devices
  • Right click and select and uninstall
  • Check "Delete the driver software for this device" and click OK
  • Windows will re-install the default driver the next time you connect the camera

Installing LibUSB ManuallyEdit

If you are using an OS prior to Windows 8.1 and don't want to use Zadig, you can install libusb manually instead.

  • Windows 8 users should read the following guide: How to install an unsigned driver on Windows 8
  • Download the latest binary release from here
  • Extract archive
  • Connect camera via USB and turn on in Play mode
  • Let Windows install its built-in driver if not already installed
  • Run \bin\inf-wizard.exe from extracted archive
  • Select your camera from the list of attached USB devices
  • Hit Next and save the resulting INF file to a new folder
  • Hit Install Now...
  • It should appear in Device Manager as libusb-win32 devices > Canon Digital Camera
  • No PC reboot is needed

LibUSB NotesEdit

  • Installing the LibUSB driver normally prevents you from accessing the camera with standard windows software, so when it is installed, you will need to use one of the CHDK client programs to download files. If you want to go back to standard software, see the removal instructions above.
  • The installed driver is specific to the selected model. If you use more than one camera model with CHDK PTP clients, you may need to install a driver for each one.
  • Depending on the camera, the driver installation may be specific to the particular physical USB port. In this case, plugging the camera into a different port will allow you to access the camera using normal windows software. This probably applies to older cameras (vxworks?)
  • You may be able to get the filter driver to work on some OSes (XP) but the Zadig or INF wizard driver is strongly recommended.

Client applications Edit

As described above, a client program compatible that implements the CHDK protocol is required to access these features

ptpcam Edit


1) download and install libusb (see install instructions above)
2) go here (German CHDK forum topic on the development of ptpcam with CHDK extensions)
3) download at the end of the first message.

The version of ptpcam available in the forum link has CHDK extensions added to communicate to the CHDK code on your camera. This is a derivative of the official ptpcam available at (the CHDK extensions are not included in the official version of ptpcam).

If you are comfortable writing batch scripts (or perl/python/... scripts) for your PC, ptpcam can be used to download jpg files and upload lua scripts and execute CHDK lua scripts on your camera all while your camera is carefully lined up on your subject and mounted to a tripod (when, for most Canon cameras, removing the memory card is not possible).

Keep in mind the fact that commands sent to your camera via ptpcam will take more time to complete than it takes for ptpcam to return control to your script. So make sure that after you issue a ptpcam --chdk="blah blah" command, that you have inserted a delay in your (batch file, perl, ...) script running on your PC to give the camera time to finish its business before you go poking the camera again.

See PTP Extension/ptpcam Examples for some examples.

A version of ptpcam is maintained in the chdkde source tree, with builds available from the chdkde forum (download The ptpcam executable may be built for Windows or Linux.

ptpCamGui Edit



ptpCamGui is a graphical front end for ptpcam. Builds are available from the chdkde forum It's also part of CHDK Shell.

A forum thread including descriptions can be found here.

The source code for the frontend and the DLL is available on the ptpCamGui assembla project.

ptpCamGui is only available for Windows.

English translation of instructions for using can be found here. Note that despite coming from a German site, both English and German languages are supported in the same .exe and are set automatically (based on your Windows installation language setting).

First time users note that the big red camera icon is used both to enter camera mode and to shoot (when radio buttons to right select "Photo").

chdkptp Edit


chdkptp is a client created specifically for controlling CHDK cameras. It provides CLI and optional GUI based on IUP

chdkptp also provides a Lua API for the CHDK protocol on the PC. Because the GUI and CLI are also implemented in Lua, this makes chdkptp easy to extend and enables end users to implement complex interactions with code on the camera.

CHDK 1.1 remote display and CHDK 1.2 remote capture are supported.

Source and builds are available on the chdkptp assembla project. A thread in the chdk forum is available for support and discussion.

Build instructions are available in README.TXT in the source. Usage information is available in USAGE.TXT

chdkptp is currently considered alpha because functionality and APIs are subject to change. However, the snapshot builds are generally stable and suitable for everyday use.

The chdkptp code is based on the CHDK fork of ptpcam, but it does not use the same commands or command line options.

Platforms Edit

chdkptp is developed for MS Windows, Linux on x86/x64 and raspberry pi.

Additional Platforms Edit

OSX Edit

Several users have reported successfully building and running chdkptp under OSX. See README-OSX.TXT in the source for more information. chdkptp is not developed for or tested by the developer on OSX, so this may be out of date. Patches, comments and corrections welcome.

Other ARM SBCs Edit

Work is also on its way to get as least the CHDKPTP CLI running on an ODroid XU board and a BeagleBone Black. Help to make that a reality is appreciated, more information here :


Arch Linux Edit

chdkptp package is available from AUR, see package page.

Usage notes Edit

Windows Edit

In order to get CHDK clients to work properly you might need to disable the "Canon Camera Access Library" service (or, if that doesn't work, the "WIA" service).

Linux Edit

Make sure you've got access to USB; in some cases this means switching to root (or changing permissions). Some information can be found in this post:

If your distro's default configuration accesses the camera on connect, this may put the camera in a state where some functionality (such as switching to shooting mode) is not available, or prevent CHDK clients from accessing the camera. The camera screen generally goes black when this happens. See for additional information

FAQ Edit

  • The computer does not recognize the camera at all, chdk client software does not connect.
Make sure USB Remote is disabled.
  • Download/upload fails with code 0x2ff or the camera crashes when you try to transfer a file
Perhaps you didn't correctly specify the file on the camera. Always use the full path and start with a capitalised 'A'. For example: "download A/DCIM/100CANON/IMG_1234.jpg test.jpg"
note this mainly applies to ptpcam, chdkptp corrects the names for you.
  • The canon firmware does not recognize key presses (real or from script) when PTP is connected
There are two known workarounds:
  • Switch to record mode using switch_mode_usb script function. Keys will still be enabled if you switch back to play.
  • On many DryOS cameras, post_levent_to_ui(4484) will also unlock the keys.
  • The camera crashes after using remote shooting and switching back to play mode.
This is a known issue on some cameras, see User:Nafraf/RemoteShootIssues and
  • Switching to shooting mode fails, and the camera screen goes black when you plug in the USB cable.
This is usually the issue described in the Linux section, caused by default Linux software accessing the camera on connect. It can also happen on windows if you don't use the INF driver.

Development history Edit

The original PTP Extension was contributed by mweerden. At mweerden's github one can find the original sources as well as a follow-up attempt at a minimal version for inclusion in the SVN trunk. The proposal version, with some minor modifications, has been included in CHDK trunk since changeset 957. ewavr made additional contributions, including the first "live view" functionality and GUI client. You can find files related to this work on ewavr's site.

The full history can be found in the PTP development thread on the forum.

Useful External Links Edit