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 Scanning barcodes using Arduino and USB Host Shield An addition of Human Input Device Class support to USB Host Shield library 2.0, announced several days ago allows using powerful and inexpensive input devices with USB interface in Arduino projects. Sample sketches demonstrating sending and receiving data to one of the most useful HID device types – boot keyboard/mouse, has been released along with the library. The beauty of boot protocol lies in the simplicity of device report – a data packet containing information about button presses and mouse movements. However, samples were designed to demonstrate all features of the class and because of that, they are somewhat heavy. In real-life applications, it is often not necessary to implement each and every virtual function – only what is needed. In today’s article I will show practical application of HID boot device building a simple gadget.
Originally, HID boot protocol was meant to be used with keyboards and mice. When USB became popular, other keyboard-emulating devices, such as barcode scanners and magnetic card readers have been migrated from PS/2 standard to USB while keeping their keyboard-emulating property. As a result, many modern “not-so-human” input devices behave exactly like a keyboard including boot protocol support. A gadget that I demonstrate today is portable autonomous barcode scanner built using Arduino board, USB Host shield, handheld USB barcode scanner and LCD display (see title picture). The operation is simple – when handheld scanner button is pressed, it scans the barcode and sends it to Arduino symbol by symbol. Arduino then outputs these symbols on LCD display. LCD is erased before outputting each new barcode by tracking time between arrival of two consecutive symbols. To keep the code simple, I intentionally did not implement any data processing, however, since Arduino sketch for the gadget compiles in just a little over 14K, there is plenty of memory space left for expansion.
Continue reading Connecting barcode scanner to Arduino using USB Host Shield
 HID r.2.0 released I pleased to announce that after a long and difficult development period Human Input Device AKA HID class support has been added to USB Host Shield Library r.2.0 and is available on gitHub – I suggest downloading the whole directory, since some modifications has been also made to core files to accommodate a new class. HID devices include popular devices like keyboards, mice, joysticks, game controllers, bar code scanners, RFID and magnetic card readers, digital scales and UPSes, to name a few.
I previously wrote about interfacing to HID devices here, here, and here. The code examples in these articles were written for legacy USB Host Shield library and can’t be compiled with current revision, however, the basic principles are the same – the device is periodically polled by the host and sends back data block called report containing changes in device controls (buttons, switches, jog dials etc.) since the last poll. Even though different devices have different report formats, for a certain device, report format is stored in the device in data structure called report descriptor. Therefore, it is possible to learn about device controls from the device itself by parsing its report descriptor.
There is one special case where report format is known in advance. Almost all HID keyboards and mice support so-called boot protocol intended for communication to very simple systems like PC configuration screen when computer runs from BIOS. Keyboard boot protocol report consists of 8 bytes containing state of modifier keys (CTRL, SHIFT,etc.) in the first byte, second byte being reserved, and up to 6 key scan codes in the rest of the report. Mouse boot protocol report consists of 3 bytes, first of which contains state of left, right and middle buttons and other 2 store X and Y travel since last poll.
In many cases boot protocol capabilities are more than enough for an Arduino project; for this reason, boot protocol class is the first to be released. To demonstrate operations of this class, 2 simple sketches has been developed, one for mouse, another for keyboard.
Continue reading HID support for USB Host Shield Library 2.0 released
 Focus Stacking Assistant var.Mini After spending a week with focus stacking assistant I realized that I need more units. I’d like to have one unit dedicated for studio work, another to carry in camera bag and yet another one to control my Nikon (code for which I’m hoping to finish soon). Full-size Arduinos are big and expensive and I wanted this controller to be cheap and portable so I built my next controller using Arduino Pro Mini 3.3V, USB Host Mini, and a small home made PCB with buttons and LED. Finished mini-assistant can be seen on title picture and uses the same code as its big brother. What follows is a build log of mini-controller. It follows traditional layout, used, for example, here – a sandwich where Arduino Pro Mini sits on top of USB Host Mini. In addition to that, I needed to add another board on top of the sandwich to carry control and indication bits.
 Step 1. The base.
Continue reading Focus stacking assistant var.Mini – build log
 Focus Stacking Assistant [EDIT] Here is a build log of mini-variant of this device.[/EDIT]
One of my favorite shooting techniques is focus stacking. Many pictures on Circuits@Home site are made using this technique. I use Helicon Focus for post processing and even though this program has camera control built-in, it obviously requires a computer close to the object of shooting. In order to be able to control my camera in the field, I wanted to replace a laptop with simple lightweight controller able to move focus of camera lens and take pictures between steps. In this article, I will show how to build one from Arduino, USB Host Shield and several small parts.
Finished circuit can be seen on the title picture. As you may already have guessed, the sequence of shots used to produce the picture has been made with the very unit depicted on it. Focus stacking assistant is controlled by 3 buttons: first moves focus towards the camera, second moves focus away from the camera, third button starts shooting sequence. Long press on focus move button sets “near” of “far” points, after both points are set shooting sequence can be run – it always starts from “near” point. The sequence can be stopped at any time by pressing on any of focus move buttons. It is important to understand that after a point is set, subsequent focus moves must be performed with focus move buttons only.
The controller can also be set to “free run” mode. Long press on third button starts shooting sequence from current lens position (which in this case can be set by hand using lens’ focusing ring) towards infinity and will run indefinitely. It can be stopped at any moment by pressing on a focus move button.
A single LED shows states of the controller. Short blink once a second indicates “idle” state – controller is connected to the camera, PTP session is open. Continuous frequent blinking means some kind of an error – most likely, controller not being able to initialize the camera or open PTP session. 3 short blinks act as a feedback to long press, focus move, etc. Additionally, more detailed diagnostic is output to Arduino serial console.
Even while connected to the camera, Focus Stacking Assistant allows camera buttons to function as usual. For example, camera LCD can be turned on and zoom area can be moved to the area of interest and then zoomed in to help focusing. Shooting mode, as well as aperture/shutter speed/ISO can be changed. It is also possible to access or erase images on the card and perform other manipulations as necessary.
Continue reading Focus stacking assistant for EOS cameras
 ADK Teminal
This is a little Android application providing basic terminal emulator functionality over ADK interface. Its primary purpose is to be able to use Android phone as laptop replacement while debugging Arduino projects in the field. It can also be used to provide simple alphanumeric display. Victor Serbo, my long time friend, helped develop this application. It can be downloaded from here and currently in beta – as soon as code stabilizes I will make source code available. [EDIT] The source code is now available. It is released under GPL2, if you modify it, please make your modifications available. [/EDIT]
When Arduino is connected to the phone via USB Host Shield, it can send characters to the application’s screen and receive characters typed on application’s keyboard. Standard CR and LF control codes are also recognized so it is possible to output, for example, single line with changing content. Additionally, the appearance and behaviour of the screen can be customized – font size and type, foreground and background colors, local echo, screen rotation and more. The app has been thoroughly tested on Nexus One and Nexus S phones and works well.
Two demo sketches has been posted to gitHub. The functionality of term_test can be seen on title picture – strings sent from Android are output back on the screen. The term_time sketch demonstrates single line output. Below is brief explanation of ways to provide input/output on Arduino. I’ll start with term_test; all necessary functionality is implemented in loop().
Continue reading Android ADK terminal emulator for Arduino
In this article I’ll show how to build Wireless EOS Controller designed by Manishi Barosee. I’m building it for my Canons and if I like it, I’ll see if it’s possible to modify it for other camera systems. My controller is built around full-size USB Host Shield instead of Mini which Manishi used – I’m going to do some debuggung and need space to connect probes. Also, full-size shield is much easier to work with.
The design of Yanis is simple yet elegant. It consists of Arduino board, USB Host Shield and serial Bluetooth module. An Arduino sketch reads the serial port, generates camera control commands and sends them to the camera over USB. The Android application acts as a UI for the controller and sends control data over Bluetooth. Here is very basic schematic drawing of Arduino part of the controller showing necessary connections. USB Host connections are described in hardware manual and Bluetooth module connections are shown in detail below.
I’d like to start with radio link. The Bluetooth module used in this build is RN-42 from Roving networks. It is 3.3V device and its pins are not specified as 5V tolerant which means that Tx pin of standard 5V Arduino can’t be connected directly to Rx pin of [my] RN-42. Fortunately, the 5V to 3.3V level shifter on USB Host shield has 2 extra gates and I will be using one of them to “condition” the Tx. To do this, I need to cut ground trace going to pin 9 of D6 (marked ‘HCT’ on the PCB), connect it to Arduino pin 1 and then connect pin 8 of D6 to Rx of RN-42.
 Cut pin 9 |
 Tx to level shifter |
Continue reading Building YaNis Android Wireless EOS Controller
 PTP ver.2 Digital camera control code AKA PTP (Picture Transfer Protocol) compatible with USB Host Shield rev.2.0 Arduino library has been released and posted to GitHub. New code has all functionality of original camera control library and adds new elements, namely ability to control several cameras simultaneously and (finally!) support for Nikon DSLRs.
The code comes with numerous examples demonstrating various aspects of digital camera control. All examples were compiled using Arduino IDE rev.0022 with USB Host Shield 2.0 and PTP 2.0 libraries installed as usual (by copying the whole library directory in %arduino%/libraries) and tested on Arduino UNO equipped with USB Host Shield. There are also several examples which require Quantum Platform state machine framework, they can be recognized by qp_port.h header included in the text of the sketch. If you want to try one of those, install QP Development Kit for Arduino and then replace qp_port.cpp with this file.
More detailed explanation of library examples will follow soon. In the mean time, play with the library and try the examples. Stay tuned for the updates!
Oleg.
 ADK code
Google Open Accessory Interface is now included in USB Host Shield Library 2.0 package. It follows standard structure of rev2.0 device driver (wherever possible) and because of this is slightly different from original Arduino code developed by Google. The interface itself is pretty simple and there are many articles on the net describing it in details; in this article I will give brief overview of new code and explain the differences.
To test the code I made a little “shield” resembling Google’s one. Since the only thing I cared about while testing was data transfer in both directions, I implemented just one LED and one button. The demokit_20.pde Arduino sketch works with DemoKit.apk Android application, however, only “B1″ button and “LED 1 Red” are functional. To run the sketch, you will need an Arduino board, USB Host Shield, as well as USB Host Shield 2.0 library.
The ADK class contains all necessary functionality to communicate to Android phone via ADK interface. In order for USB subsystem to initialize the device when it is connected, the instantiation should look like the following code fragment. First, the USB class is instantiated, then ADK is instantiated taking address of USB instance as the first parameter. The rest of the parameters are ID strings for the phone – they are identical to the original code.
The initialization of Android device and switching it to accessory mode is performed automatically by USB subsystem. The ADK::Init() member function is called each time a new device is detected on a bus. It first tries to determine if a device is in accessory mode already by reading its VID, PID, and if yes, configures it and reports success to the system. If device fails accessory check, the standard probing and accessory switching method is performed. If successful, device resets and appears on USB bus as an “accessory mode-capable” unit. In certain cases, Init() may be executed two times.
Continue reading Google Open Accessory Interface for USB Host Shield Library 2.0 released
 Navibee GM720 connected to Arduino
Here is another quick demonstration of USB Host Shield 2.0 Library. This article describes how to communicate to Navibee GM720 GPS receiver based on SiRF Star III chipset and PL2303 USB to serial converter. This GPS device is available on eBay for around $25 new, used units can sometimes be found for $10 or even less. The receiver has waterproof case, magnet mount and comes with 6 foot cable. Another nice feature of this device is its 40mA current consumption. Here are some pictures of the unit – PCB, internal antenna, as well as front and back of the original packaging.
“Classic” GPS receiver sends and receives NMEA 0183 messages via serial port at 4800 bps. Modern GPS units often support faster speeds and vendor-specific messages. However, they mimic classic GPS unit behavior – at power-on they start sending basic navigation messages at 4800 bps. The following sketch outputs messages, received from Navibee GM720 GPS unit via its built-in PL2303 USB to serial converter connected to USB Host Shield. Full text of the sketch is available on gitHub, below is just a fragment where speed is set to 4800.
The OnInit() member function is called to change serial parameters after initialization. A lc structure of type LINE_CODING is declared on line 14. It is filled with baud rate (line 15) and number of data bits per byte (line 18) and then sent to Pl instance in line 20.
Compile the sketch, load and run. The output is depicted on a screenshot after the code fragment.
Continue reading Communicating to GPS Receiver using USB Host Shield
 Motorola RAZR talks to Arduino
One of the main motivations for adding asynchronous CDC support code to rev.2.0 of USB Host Library was to be able to use cell phones in Arduino projects – establish simple data exchange via SMS, take pictures or connect to the Internet. Second hand phones are inexpensive yet quite capable. Also, m2m (machine to machine) SIM cards start at $4-$6/mo, some even allow for free incoming SMS. All that makes a cell phone an attractive communication option for hobby projects. In this post, I will be talking about basics of cell phone control using data port and AT commands. I will also present simple terminal emulator sketch – to use the code you will need an Arduino board, USB Host Shield, as well as USB Host Shield 2.0 library.
Modern (<10 year old) phones have standard GSM chip interface implemented and accessible via so-called “data port”. The oldest phones implement TTL level asynchronous serial interface by means of “custom” USB data cable, which is just proprietary connector on one end, standard USB connector on the other end, and USB-to-serial converter chip (almost always Prolific PL2303) between them. Newer cell phones have USB-to-serial converter built-in. Motorola phones usually terminate data port on standard mini-USB connector, others, like Samsung and Sony Ericsson, use proprietary cable. The USB-to-serial converter in these phones is almost always standard CDC ACM type.
Many functions of the phone can be accessed by AT commands, similar to commands used to control Hayes phone modems. Standard GSM commands are defined in 3GPP TS 07.07 (look for the latest version, which is 7.8.0). Cell phone manufacturers also define their own AT commands. In documentation AT commands are usually presented in uppercase, however, most phones accept lowercase just as well. A command shall be followed by CR,LF (usually Enter key). If a command is accepted, OK is returned, along with response. If command is not recognized, ERROR is returned. Some commands will be accepted in certain phone states and rejected in others.
Continue reading Interfacing Arduino to a Cellular Phone
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