{"id":13408,"date":"2024-11-21T01:42:36","date_gmt":"2024-11-21T06:42:36","guid":{"rendered":"http:\/\/engineersgarag-main\/atmega-32u4-based-edit-keypad-part-4-25\/"},"modified":"2024-11-21T05:46:21","modified_gmt":"2024-11-21T10:46:21","slug":"atmega-32u4-based-edit-keypad-part-4-25","status":"publish","type":"post","link":"https:\/\/www.engineersgarage.com\/atmega-32u4-based-edit-keypad-part-4-25\/","title":{"rendered":"Atmega 32u4 Based Edit Keypad (Part 4\/25)"},"content":{"rendered":"

In <\/span>Atmega 32u4 based Generic USB Keyboard project<\/strong><\/a> is already learnt that How a generic USB Keyboard is made. Building upon the same project, this project is about building a special keypad to interact with the windows operating system. The keypad will be called Edit keypad and will have three buttons to do cut copy and paste functions. On a typical generic keyboard, for doing cut copy and paste, combination of keys is required to press together. The edit keypad will do the stated operations just by pressing individual keys of the keypad. The project utilizes 8-bit USB AVR – Atmega 32u4 as the USB controller chip and uses AVR based Lightweight USB Framework (LUFA) as the firmware which is modified to work for the edit keypad.<\/span><\/p>\n

\"Prototype<\/span><\/p>\n

Fig. 1:\u00a0Prototype of Arduino based DIY Editing Special USB Keyboard for Windows<\/em><\/p>\n

The LUFA firmware is used and its HID device driver class for keyboard is modified to program the project. The edit keypad has the keys for the following tasks – :<\/p>\n

\u2022 Cut selected item or text<\/p>\n

\u2022 Copy selected item or text<\/p>\n

\u2022 Paste selected item or text<\/p>\n

The project is developed to work with the windows operating system and has been successfully tested on it. \u00a0The keypad works on the windows based office applications for text editing as well provided the application has the same shortcut keys assigned for the edit operations as the default windows system.<\/p>\n

The project uses tactile switches as keypad buttons, Atmega 32u4 as the controller chip (on board Arduino Pro Micro) and USB cable to connect with the personal computer.<\/p>\n

PREREQUISITES<\/h4>\n

This project is based on Arduino Pro Micro which has the USB AVR – Atmega 32u4 as the sitting MCU. In order to understand this project, one must have basic knowledge of the AVR microcontrollers and the embedded C programming for AVRs. WinAVR Studio is used to write, edit and compile the project code, so closely following the project shall require familiarizing with the above stated IDE as well. Though LUFA framework takes care of implementing the USB protocol and has APIs to abstract the lower level codes, understanding USB protocol<\/strong> is recommended to understand how actually the project is working. In fact, if anyone has already worked on some other microcontroller, it will not be much pain to understand and follow this project as the project code is more or less about getting input from the GPIO pins of AVR MCU and modifying the LUFA device driver of generic keyboard accordingly.<\/p>\n

\"Image<\/p>\n

Fig. 2:\u00a0<\/em>Image showing Editing Special USB Keypad in use on Windows PC<\/span><\/p>\n

COMPONENTS REQUIRED<\/h4>\n

1. Arduino Pro Micro<\/p>\n

2. Breadboard<\/p>\n

3. Connecting wires<\/p>\n

4. Push buttons<\/p>\n

5. Micro USB cable<\/p>\n

6. 10K resistors<\/p>\n

SOFTWARE TOOLS REQUIRED<\/h4>\n

1. WinAVR Studio<\/p>\n

2. AVR Dude<\/p>\n

3. LUFA Firmware<\/p>\n

BLOCK DIAGRAM<\/strong><\/p>\n

 <\/p>\n

\"Block<\/p>\n

Fig. 3:\u00a0\u00a0<\/em>Block Diagram of Arduino based DIY Editing Special USB Keyboard for Windows<\/span><\/p>\n

CIRCUIT CONNECTIONS<\/span><\/strong><\/p>\n

The project uses Arduino Pro Micro as the USB controller chip. A set of three tactile switches are connected at the port B of the Arduino. The switches are connected at pins 4, 5 and 6 of the port B with functions assigned to them according to the following table – :<\/p>\n

\"Table<\/p>\n

Fig. 4:\u00a0<\/em>Table listing Editing functions and Key Combinations<\/span><\/p>\n

The tactile switches are connected between the port and ground. The pins of port B by default are connected to VCC and receive a HIGH logic. Pressing a tactile switch changes the status at the respective pin to LOW by short circuiting to the ground.<\/p>\n

The Program code for the project is burnt to the Arduino Pro Micro using AVR Dude. The Arduino board is connected to the USB port of a PC by a USB cable.<\/p>\n

HOW THE PROJECT WORKS<\/h4>\n

For configuring the controller chip to work as a Keypad controller, the HID Class Driver for keyboard of the LUFA framework is employed. The Human Interface Device (HID) class takes care of the transfers between the host device and the human controlled USB peripherals like USB Keyboard, Mouse or Joystick. The implementation of the USB protocol is carried out by the open-source drivers of the LUFA framework.<\/p>\n

Like any HID device, when the edit keypad is attached to the host computer (PC), the host sends request for configuration details in the form of control transfer. The controller chip on keypad has to respond with appropriate descriptors to get configured and ready for further operations. Only after configuration, the keypad can transfer user inputs with the host in the form of interrupt transfers for executing the desired operations on the windows OS. The process of identification and configuration of any USB device with the host is called enumeration.<\/p>\n

\"Image<\/p>\n

Fig. 5:\u00a0<\/em>Image showing Editing Special USB Keypad in use on Windows PC<\/span><\/p>\n

Any device using HID class for keyboards identifies the key pressed by the keycode or combination of keycodes sent from the controller chip of the device to the host in the data input report. Any keyboard device sends a usage report and data input report to the host and receives data output report from the host at the application layer to work like a keyboard. The reports are a medium at application layer as per the USB protocol to facilitate enumeration and communication between the host and the device. To learn about HID Class for Keyboard and how the usage report, data input report and data output report are structured in the HID Class for Keyboard, go through the Atmega 32u4 based Generic USB Keyboard project<\/strong>. To learn about the keycodes assigned to different ASCII characters and modifier keys on a generic keyboard, check out the HID Usage Table provided by the USB Implementers Forum<\/strong>.<\/p>\n

The keycode that have to be passed to the host on pressing a key is managed by the program code of USB controller chip. Even a combination of keycodes can also be passed to the host on pressing key if the program code of the USB controller chip has the provision for that. This project uses the same feature. While on a generic keyboard, a set of keys is required to press together for passing a combination of keycodes (Maximum six keycodes along with a modifier key can be passed in a single data input report) to the host. In this project, the controller chip is programmed to pass the required combination of keycodes on pressing single key at a time (which on typical keyboard is passed on pressing a combination of keys together). The buttons on the keypad passes the keycodes for the following keys altogether – :<\/p>\n

\"Table<\/p>\n

Fig. 6:\u00a0Table listing Arduino pins and respective keypad functions and executable key combinations<\/em><\/p>\n

This keypad is just a custom built keyboard. A keyboard is HID class USB device and LUFA framework has HID class related modules \u00a0in the LUFA-Source-Folder \/LUFA\/Drivers\/USB\/Class\/Device folder. Other device class related module are also in the same folder. The LUFA framework has demo projects for different USB device classes in the LUFA-Source-FolderDemosDeviceClassDriver folder. For implementing the project, demo project for keyboard provided in the LUFA framework is modified and complied. The demo project for keyboard is in the LUFA-Source-FolderDemosDeviceClassDriverKeyboard folder. The folder contains keyboard.c file which will be modified to work for the custom edit keypad.<\/p>\n

How Keyboard.c identifies HID device being Keyboard<\/u><\/h4>\n

The keyboard.c uses Keyboard_HID_Interface interface in HID_Device_USBTask() function which is being imported from the HIDDeviceClass.c (from LUFA-Source-Folder LUFADriversUSBClassDevice) to configure the device as keyboard. The interface abstracts the low-level descriptor codes and identifies the device as keyboard through an InterfaceNumber variable.<\/span><\/p>\n

From Where Keyboard.C gets the USAGE and Data Reports Descriptors<\/u><\/h4>\n

In the LUFA framework’s demo project for Keyboard, descriptor.c file is imported in keyboard.c to send the relevant usage and data reports descriptors to the host device. The descriptor.c defines a KeyboardReport[] structure \u00a0which is used in the CALLBACK_HID_Device_CreateHIDReport() function of the keyboard.c to generate keyboard specific usage and data reports descriptors. Inside descriptor.c the KeyboardReport[] structure has the values returned by HID_DESCRIPTOR_KEYBOARD () function. The HID_DESCRIPTOR_KEYBOARD() is defined in HIDClassCommon.h (located in LUFA-Source-FolderLUFADriversUSBClassCommon folder). The keyboard.c imports keyboard.h which imports usb.h. USB.h imports HIDCLass.h. In HIDClass.h is imported HIDClassDevice.h if the USB_CAN_BE_DEVICE is true for the controller chip to being a USB device not the host. The HIDClassDevice.h imports HIDClassCommon.h where the HID device specific descriptor fields have been defined.<\/p>\n

\"Image<\/p>\n

Fig. 7:\u00a0<\/em>Image showing implementation of Cut Function by Editing Special USB Keypad<\/span><\/p>\n

HOW THE DEVICE WORKS<\/u><\/h4>\n

The AVR microcontroller is programmed to get the user inputs from the tactile switches that work as the keypad buttons. The main() function and CALLBACK_HID_Device_CreateHIDReport() function of the keyboard.c are modified to customize the program code to send the respective combination of keycodes in the data input report. Check out the program code to see the modifications implemented for this customized edit keypad.<\/span><\/p>\n

PROGRAMMING GUIDE<\/span><\/h4>\n

For building the project download the LUFA framework<\/a> from the github.com.\u00a0<\/span>The demo project provided with the LUFA framework is modified to make this edit keypad. In the extracted LUFA zip file, open Demos\/Device\/ClassDriver\/Keyboard folder. The folder has the following files and folders.<\/span><\/p>\n

\"Screenshot<\/span><\/p>\n

Fig. 8:\u00a0<\/em>Screenshot of LUFA Library Folder on Windows<\/span><\/p>\n

Of these, Keyboard.h, Keyboard.c and Makefile needs to be modified for this project.\u00a0<\/span>The modified files (provided at the bottom of the article in zip format) can also be downloaded from the engineersgarage and replaced with the original files.<\/span>\u00a0Either open the files in WinAVR Studio or Notepad++ and modify original files or replace files with the already modified one. The modified or replaced Keyboard.c needs to be compiled from within the LUFA’s Source folder to get the object code.<\/span><\/p>\n

Modifying Keyboard.h<\/span><\/u><\/h4>\n

The Keyboard.h library file is imported in the Keyboard.c file and includes a set of additional libraries and defines the constants and functions for the keyboard device. These include the additional libraries for the joystick, button and LEDs which should be commented out as the project is not using these HID features. So open Keyboard.h and make the following changes – :<\/span><\/p>\n

\u2022 Comment the #include library statements for Joystick.h, LEDS.h, and Buttons.h (The include statements for these libraries are commented as any joystick, buttons board and LED board is not used in the project)<\/span><\/p>\n

\u2022 Comment the #define statements for LEDMASK_USB_NOTREADY, LEDMASK_USB_ENUMERATING, LEDMASK_USB_READY, LEDMASK_USB_ERROR<\/div>\n

Save the file with changes.<\/p>\n

Modifying Keyboard.C file<\/u><\/h4>\n

Again in the Keyboard.c, the code sections for Joystick, button board and LEDs need to be commented out. \u00a0So open Keyboard.c and make the following changes – :<\/span><\/p>\n

\u2022 In the main loop, comment the LEDs_SetAllLEDs()<\/span><\/p>\n

\u2022 In SetupHardware() function, comment the Joystick_Init(), LEDs_Init(), Buttons_Init()<\/p>\n

\u2022 In EVENT_USB_Device_Connect() function, comment the LEDs_SetAllLEDs()<\/p>\n

\u2022 In EVENT_USB_Device_Disconnect() function, comment LEDs_SetAllLEDs()<\/p>\n

\u2022 In EVENT_USB_Device_ConfigurationChanged() function, comment the LEDs_SetAllLEDs()<\/p>\n

In Keyboard.c the main() function executes the functioning of the Keypad. Inside the main function, Port B where the tactile switches have been connected needs to be defined as input and all the pins of port B has to be raised to HIGH logic by default as the microcontroller will need to detect LOW logic for input from the tactile switches. Therefore, modify the body of main() function as the code given below – :<\/p>\n

\u00a0 \u00a0 \u00a0 \u00a0int main(void)<\/div>\n
{<\/div>\n
\u00a0 \u00a0 \u00a0 SetupHardware();<\/div>\n
\u00a0 \u00a0 \u00a0 DDRB = 0x00;<\/div>\n
\u00a0 \u00a0 \u00a0 PORTB = 0xff;<\/div>\n
<\/div>\n
\u00a0 \u00a0 \u00a0 \/\/LEDs_SetAllLEDs(LEDMASK_USB_NOTREADY);<\/div>\n
\u00a0 \u00a0 \u00a0 GlobalInterruptEnable();<\/div>\n
<\/div>\n
\u00a0 \u00a0 \u00a0 for (;;)<\/div>\n
\u00a0 \u00a0 \u00a0{<\/div>\n
\u00a0 \u00a0 \u00a0 \u00a0 HID_Device_USBTask(&Keyboard_HID_Interface);<\/div>\n
\u00a0 \u00a0 \u00a0 \u00a0 USB_USBTask();<\/div>\n
\u00a0 \u00a0 \u00a0}<\/div>\n
}<\/div>\n
<\/div>\n
The statements should be added before the infinite loop otherwise the microcontroller ports could not be configured for the user inputs.<\/div>\n
Inside the infinite for loop the HID_Device_USBTask() function is called where Keyboard_HID_Interface interface is passed as parameter. The interface identifies the device as keyboard and abstracts the low level program code specific to keyboard HID class. The function is coming from the HIDClassDevice.c module (located in LUFA\/Drivers\/USB\/Class\/Device\/HIDClassDevice.c) and is used for general management task for a given HID class interface, required for the correct operation of the interface. It should be called in the main program loop, before the master USB management task USB_USBTask(). The \u00a0USB_USBTask() is the main USB management task. The USB driver requires this task to be executed continuously when the USB system is active (device attached in host mode, or attached to a host in device mode) in order to manage USB communications. The function is defined in USBTask.c (Located in LUFA-Source-FolderLUFADriversUSBCore folder)<\/div>\n

For creating Keyboard Data Input report to pass the desired combination of keycodes according to the pressed keypad button.CALLBACK_HID_Device_CreateHIDReport() needs to be modified. The default file has the function body to detect joystick movement as well.<\/p>\n

\"Screenshot<\/p>\n

Fig. 9:\u00a0Screenshot of CALLBACK_HID_Device_CreateHIDReport Function in LUFA Library<\/em><\/p>\n

The edit keypad is using tactile switches to get the hint of keycode combination that needs to be passed. Therefore, LOW bit at each button is detected and the corresponding keycode combination is sent via data input report for the keyboard HID Class. So replace the body of the CALLBACK_HID_Device_CreateHIDReport() function with the following code -:<\/p>\n

bool<\/div>\n
CALLBACK_HID_Device_CreateHIDReport(USB_ClassInfo_HID_Device_t* const HIDInterfaceInfo,<\/div>\n
\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0uint8_t* const ReportID,<\/div>\n
\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0const uint8_t ReportType,<\/div>\n
\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0void* ReportData,<\/div>\n
\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0uint16_t* const ReportSize)<\/div>\n
{<\/div>\n
\u00a0 \u00a0 \u00a0 USB_KeyboardReport_Data_t* KeyboardReport = (USB_KeyboardReport_Data_t*)ReportData;<\/div>\n
<\/div>\n
<\/div>\n
\u00a0 \u00a0 \u00a0 uint8_t UsedKeyCodes = 0;<\/div>\n
<\/div>\n
\u00a0 \u00a0 \u00a0 if(!(PINB & _BV(PB4))) {<\/div>\n
\u00a0 \u00a0 \u00a0 \/\/ change report for cut functionality<\/div>\n
\u00a0 \u00a0 \u00a0 \/\/ add keycode for \u2018x\u2019 alphabet in the report<\/div>\n
\u00a0 \u00a0 \u00a0 KeyboardReport->KeyCode[UsedKeyCodes++] = HID_KEYBOARD_SC_X;<\/div>\n
\u00a0 \u00a0 \u00a0 \/\/ add keycode for modifier ctrl key in the report<\/div>\n
\u00a0 \u00a0 \u00a0 KeyboardReport->Modifier = HID_KEYBOARD_MODIFIER_LEFTCTRL;<\/div>\n
<\/div>\n
\u00a0 \u00a0 \u00a0 \u00a0}<\/div>\n
\u00a0 \u00a0 \u00a0 else if(!(PINB& _BV(PB5))) {<\/div>\n
\u00a0 \u00a0 \u00a0 \/\/ change report for copy functionality<\/div>\n
\u00a0 \u00a0 \u00a0 \/\/ add keycode for \u2018c\u2019 alphabet in the report<\/div>\n
\u00a0 \u00a0 \u00a0 KeyboardReport->KeyCode[UsedKeyCodes++] = HID_KEYBOARD_SC_C;<\/div>\n
\u00a0 \u00a0 \u00a0 \/\/ add keycode for modifier ctrl key in the report<\/div>\n
\u00a0 \u00a0 \u00a0 KeyboardReport->Modifier = HID_KEYBOARD_MODIFIER_LEFTCTRL;<\/div>\n
\u00a0 \u00a0 \u00a0 }<\/div>\n
<\/div>\n
\u00a0 \u00a0 \u00a0 else if(!(PINB & _BV(PB6))) {<\/div>\n
\u00a0 \u00a0 \u00a0 \/\/ change report for paste functionality<\/div>\n
\u00a0 \u00a0 \u00a0 \/\/ add keycode for \u2018v\u2019 alphabet in the report<\/div>\n
\u00a0 \u00a0 \u00a0 KeyboardReport->KeyCode[UsedKeyCodes++] = HID_KEYBOARD_SC_V;<\/div>\n
\u00a0 \u00a0 \u00a0 \/\/ add keycode for modifier ctrl key in the report<\/div>\n
\u00a0 \u00a0 \u00a0 KeyboardReport->Modifier = HID_KEYBOARD_MODIFIER_LEFTCTRL;<\/div>\n
\u00a0 \u00a0 \u00a0 }<\/div>\n
<\/div>\n
*ReportSize = sizeof(USB_KeyboardReport_Data_t);<\/div>\n
return false; }<\/div>\n

In the body _BV() function is used to map the respective bit as a byte with only the respective bit changed in the returned byte. In the code, the constants to represent the following generic keyboard keys are used (defined in HIDCommonClass.h, header file located in \u00a0LUFA-Source-FolderLUFADriversUSBClassCommon folder)<\/p>\n

\"Table<\/p>\n

Fig. 10:\u00a0Table listing keys and respective constants used in LUFA Library<\/em><\/p>\n

The Data Output Report is not utilized in the project execution therefore the CALLBACK_HID_Device_ProcessHIDReport() function which process Data Output report has been kept unchanged.<\/p>\n

Save the file and create Make file for the project.<\/p>\n

Modifying Make File<\/u><\/h4>\n

In the Keyboard folder there is a make file that needs to be edited. The file can be edited using Notepad++. The following information needs to be edited – :<\/span><\/p>\n

\u2022 MCU = atmega32u4<\/p>\n

\u2022 ARCH = AVR8<\/p>\n

\u2022 BOARD = LEONARDO<\/p>\n

\u2022 F_CPU = 16000000<\/p>\n

Save the file and exit. Now all the files are edited completely for the Edit Keypad project.<\/p>\n

Compiling Keyboard.c<\/u><\/h4>\n

For compiling the source code, WinAVR Programmers Notepad or Arduino IDE can be used. Open the modified Keyboard.c file and compile the code.<\/span><\/p>\n

BURNING HEX CODE<\/span><\/u><\/h4>\n

The hex file is generated on compiling the keyboard.c file. For burning the object code to microcontroller open the Command Prompt, change the current directory to the directory containing the Hex file. This can be done using command: CD <address of the directory>. Now reset the Arduino and instantly run the command: : avrdude -v -p atmega32u4 -c avr109 -P COM20 -b 57600 -D -Uflash:w:Keyboard.hex:i after replacing the COM Port with the recognized one.<\/span><\/p>\n

If the uploading process is successful, the Arduino board will be shown as HID Keyboard in the Device Manager. There is no need of installing any driver in the computer as Generic HID Keyboard is used for the project implementation. Select files or text and press the buttons to test the working of edit keypad.<\/span><\/p>\n

In the next project – Atmega 32u4 based Digital Business Card<\/strong><\/a>, learn how to make a digital business card with USB Plug In.<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

In Atmega 32u4 based Generic USB Keyboard project is already learnt that How a generic USB Keyboard is made. Building upon the same project, this project is about building a special keypad to interact with the windows operating system. The keypad will be called Edit keypad and will have three buttons to do cut copy and paste functions. On a typical generic keyboard, for doing cut copy and paste, combination of keys is required to press together. The edit keypad will do the stated operations just by pressing individual keys of the keypad. The project utilizes 8-bit USB AVR – Atmega 32u4 as the USB controller chip and uses AVR based Lightweight USB Framework (LUFA) as the firmware which is modified to work for the edit keypad.<\/p>\n","protected":false},"author":311,"featured_media":53886,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_genesis_hide_title":false,"_genesis_hide_breadcrumbs":false,"_genesis_hide_singular_image":false,"_genesis_hide_footer_widgets":false,"_genesis_custom_body_class":"","_genesis_custom_post_class":"","_genesis_layout":"","footnotes":""},"categories":[13],"tags":[],"class_list":{"2":"type-post","8":"entry","9":"has-post-thumbnail"},"acf":[],"yoast_head":"\nAtmega 32u4 Based Edit Keypad (Part 4\/25)<\/title>\n<meta name=\"description\" content=\"This project is about building a special edit keypad to interact with the windows operating system to do cut copy and paste functions.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.engineersgarage.com\/atmega-32u4-based-edit-keypad-part-4-25\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Atmega 32u4 Based Edit Keypad (Part 4\/25)\" \/>\n<meta property=\"og:description\" content=\"This project is about building a special edit keypad to interact with the windows operating system to do cut copy and paste functions.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.engineersgarage.com\/atmega-32u4-based-edit-keypad-part-4-25\/\" \/>\n<meta property=\"og:site_name\" content=\"Engineers Garage\" \/>\n<meta property=\"article:publisher\" content=\"https:\/\/www.facebook.com\/engineersgarage\" \/>\n<meta property=\"og:image\" 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