Today, I’m writing about two more pieces of digital camera control firmware that have being posted to PTP gihHub repository. Alex Gluschenko, the author of PTP library for Arduino, developed two sketches, one called EOSRemote and the other EOSCamController to demonstrate PTP library capabilities. The code allows requesting camera settings, such as shutter speed, aperture, ISO, etc., change them, as well as take shots. It supports Canon EOS cameras and was tested on EOS 400D, 450D, and 7D; other cameras with similar command set ( see my collection of PTP device info dumps ) may work as well.
This is how the code works: when connection is established, camera sends back an initial packet with all its current settings along with a list of all possible values for each setting. Possible values depend on a camera model as well as lens that are mounted. For example, some cameras may have exposure compensation range from -2 to +2, others from -5 to +5; some lens have max.aperture 1.4, others – 3.5, an so on. The list of values received from the camera is placed in built-in EEPROM of Arduino microcontroller. After that, values are used in setting (called “property” in PTP lingo) change commands sent to the camera. When camera mode, such as Av, Tv, or lens is changed, camera sends initial packet again. The Arduino code tracks changes and updates the list stored in EEPROM.
Hardware requirements for both controllers are pretty standard. The EOSRemote sketch uses Arduino serial port facility for I/O, and the only hardware necessary is Arduino Duemilanove, Uno, or compatible clone, as well as USB Host Shield. User interface is designed with simple terminal emulator program in mind. It can be used with a PC connected to Arduino directly or over some distance utilizing a pair of serial to RF converters, such as ever-popular Xbee. The following screenshot shows top-level menu with camera connected and recognized. Continue reading Arduino-based controller for Canon EOS cameras
New version of USB Host library has been uploaded to gitHub. I managed to find a couple of bugs and solve some compatibility issues. The biggest change, however, has been made on the very lowest level of the library – SPI transfers between Arduino and MAX3421E registers.
From the beginning, USB Host firmware relied on Arduino Playground SPI library. Starting from version 0018 of Arduino IDE, this library became part of the distro. Two versions after that, Arduino team decided to re-write SPI library, among other things changing function names. As a result, USB Host code became incompatible with “stock” SPI library. To remedy the situation, I incorporated SPI routines directly into MAX3421E support code. The new code is independent of Arduino SPI library and builds correctly on “old” (i.e. 0017) and “new” (0021) versions of Arduino IDE. In addition to that, new code accounts for SPI pinout difference between Arduino variants and works on both Atmega 328 and Atmega 1280/2560 based boards. ( Note: the current rev1.x USB Host Shield still needs to be modified to work with Megas )
The new library can be downloaded from USB Host Shield gitHub repository. If you are upgrading existing installation of the library, please make a backup copy before downoading! I checked it against all code examples and USB devices in my possession and everything works without a hitch. However, code written with tight timing may stop working because of speed difference since new SPI routines are slightly faster.
As you can see in the title picture ( click on it to enlarge ), the line #include "Spi.h" is no longer needed. In next several days I’m going to update all USB examples on this site to match the new code. If you have any any problems with the library, please let me know!
Another popular USB peripheral code for USB Host Shield has been implemented! Collin Cunningham from Collin’s Lab @ MAKE found a neat way of interfacing USB MIDI devices with Arduino. The video above demonstrates using Akai LPK25 keyboard and USB video game guitar to play music on Arduino. Quoting Collin, his setup is “USB MIDI to old-school MIDI converter”.
Make sure to check out Collin’s code – it’s one-piece sketch, short, clean and easy to understand. It is Richard Ibbotson’s PS3 code, re-purposed to parse MIDI data. While not a textbook implementation of USB MIDI, Collin’s code can be used to talk to MIDI keyboards, guitars, and consoles, to name a few. Good job, Collin!
Sandro Benigno from DIY Drones released camera control code for Arducam project. The goal of the project is to control Powershot camera mounted on UAV while feeding camera’s video output back to operator. Telemetry from UAV will also be sent back mixed in video using MAX7456 OSD ( on-screen display ) generator IC. Needless to say, I’m very interested in camera control side of this project.
The capabilities of the code can be seen in a video above. From my experience, Powershot cameras use identical control commands for different models so this code would work with other cameras with no or very minimal changes. For example, I tested it on my A640 and it works just fine. On the other hand, not every Powershot camera can be controlled over USB; suitable model numbers can be deduced from this gphoto list.
The project-related discussion is hosted on DIY Drones.
I am pleased to announce addition of Bluetooth dongles to the family of USB devices supported by USB Host Shield. Bluetooth dongles are affordable, interface is well documented, and USB transport layer is very simple. Even though full Bluetooth protocol is heavy and takes a lot of program space, it can be stripped down quite a bit for a particular application. One good example of such approach is Richard Ibbotson’s HID over Bluetooth implementation – see Wiimote Game Controller Interfacing article for details. I wanted to have simple communication transport over Bluetooth which would fit into Arduino and the code I’m presenting in this article is doing just that – it’s lightweight terminal program allowing two Arduinos talk to each other over Bluetooth. The code has been developed by George Lgotkin.
The source is hosted in GitHub repository. Standard Arduino library format of the code has not been tested yet, for now it’s easier to just copy all the files in a directory and open btclass_h.pde in Arduino IDE. To use the program, you need two Arduinos, two USB Host Shields, and two Bluetooth dongles. You need to compile and load the sketch into both Arduinos and then open two terminal windows, one to a serial port of each Arduino – this can be done from a single computer. Don’t use Arduino IDE built-in terminal. Also, SPI library shipped with recent versions of Arduino IDE is not compatible with USB Host library, if you have compiler errors related to SPI, replace your library with one from Arduino-0018 or the Playground. Serial port speed is set to 115200 in the sketch, it can be changed in setup(), if necessary.
Sketch starts by printing short help (see screenshot below) and then waits for the command. In order for two Bluetooth devices to talk to each other, one has to be the server and another one client. In one terminal, type ‘S’ and press Enter. This starts the server. If you are curious, type ‘M’, Enter – the address of the module will be printed. Note that if you send address request before starting the server, address containing all zeroes will be returned.
To establish connection, type ‘C’, Enter in other terminal. The sketch will print “Connecting…”. After some time ( 30 seconds or less ) both terminals will print “Connected”. Now type something in one terminal and press Enter – the string you just typed will appear in other terminal window. Easy.
This code is just a small example, error handling is minimal. It works better if no other Bluetooth radios are transmitting nearby. If client Arduino reports “Connected” but server doesn’t, it means that client has connected to some other server, most likely your laptop or phone. This can also be used to your advantage for testing – start Bluetooth on a PC and then see if both Arduinos are able to connect to it in client mode.
The first batch of USB Host Minis is built, tested, and boards are available in store. It is designed to be employed in lightweight, battery-operated circuits, for example, used for digital camera control. It can also be used as general MAX3421E breakout board. Title picture shows the board proudly sitting in its’ own ghetto-style Sparkfun-inspired pogo bed.
The design follows Arduino Mini minimalistic approach. It is 3.3V only and mates quite nicely with Sparkfun 3.3V Arduino Pro Mini. Only essential control and GPIO signals are available – no power supplies, level converters, or even jumpers are provided due to lack of space. However, since rearranging control signals is often necessary, extra pads have been placed for this purpose. They can be seen on product picture at the top and to the left of MAX3421E IC.
The board has VBUS routed to 3.3V. Even though the voltage is lower than specified 5V, the shield has been tested to work flawlessly with numerous self-powered devices, such as digital cameras, as well as some bus-powered devices, such as Sandisk Cruzer flash drive. However, if 5V VBUS is necessary, board can be easily modified – the trace from 3.3V to VBUS can be cut and 5V applied using a pad placed on the board for this purpose. It can be arranged using single 5V supply; since Arduino Pro Mini has on-board LDO, 5V can be applied to VRAW and VBUS while shield will be getting its’ 3.3V power from Arduino board, as usual.
Bottom picture shows my favourite arrangement – Arduino Pro Mini sits on top of the shield with its’ programming connector easily accessible from either side. Also, Arduino reset switch is easily accessible this way.
Project files and schematic are available in Downloads section. If you have any questions about this design, e-mail me or leave a comment here.
New version of PTP Library for Arduino USB Host Shield has been posted on GitHub. In this version, PTP::Task() has been completely rewritten to provide for non-blocking state machine-type execution. Another major addition is comprehensive support for Canon EOS cameras – many camera functions including changes of shooting parameters, Live View, focus move, are now well understood and supported. The library is released under GNU General Public License version 2.
In addition to the code library, a manual page has been created outlining EOS-specific extensions to PTP protocol, a code example, and library reference. Similar page for basic PTP functions is planned also.
The code is stable (more or less) and no application interface changes are planned at this moment. It is, however, incompatible with an old version, which is preserved in “legacy” branch of GitHub repo. The camera interface has not changed much and migration of old projects should be easy. If you have issues with migration, comment below and I will try to help.
This is the status update on Arduino USB Host Mini development, announced 3 weeks ago. I received rev.0 PCBs last Saturday – BatchPCB is faster than ever! I made a test build (see title picture) and after fixing one major and several minor mistakes placed an order for what I’m hoping will be the final pre-production sample.
The prototype was built to sit on top of Arduino Pro Mini to make access to the parts easier during troubleshooting. On the final board USB connector is placed slightly further away from the pins; it will be possible to place Arduino on top of the shield so that the height of the “sandwich” will be less or equal to the height of USB connector.
In 2-3 weeks I’m hoping to finalize the design and start producing the USB Host Mini. Stay tuned!
Many people asked me to post a video showing an arm from inverse kinematics article in action. While making a video, I realized that shots of the arm following a pattern of computer-generated coordinates is going to be less than exciting and decided to add manual control. The video below shows the result. In addition to the video, a HID introductory page has been written describing HID communication basics as well as some simple Arduino code. Enjoy! ( Youtube link, where HD quality video can be selected ).
This post announces starting of development of new Arduino USB Host Shield variant. There are several projects in the works (thanks, guys for letting me know!), where standard size Arduino board is too big. Since electronics of USB Host Shield is pretty simple, it was decided to shrink the board as much as possible. Here is the first iteration.
The initial revision of USB Host Shield in Mini form factor is shown on title picture, It is intended to be used with Sparkfun’s 3.3V Arduino Pro Mini. Intended applications include digital camera control devices, robots, as well as any other projects where size and weight has to be minimized. The Gerbers was sent to BatchPCB; I’m expecting boards back in couple of weeks. The main goals of this first prototype are manufacturability check as well as checking claims made below.
The Mini Host is simplified version of full-sized shield; only USB and GPIO are available. By default, VBUS is routed to VCC, therefore only self-powered USB devices are expected to function (even though I have at least one USB flash drive which works fine powered from 3.3V VBUS). I also provided extra pads to simplify signal re-routing, however, since there was no place left for jumpers a trace has to be cut instead. The same has been arranged for VBUS – if 5V power is necessary, Arduino Pro Mini/Shield combination can be powered with 5V on RAW pin, the VCC trace cut off VBUS and RAW and VBUS connected.
As soon as first prototype is tested, I will post CAD files and also make boards available at BatchPCB. Stay tuned!
