{"id":13417,"date":"2024-11-21T01:45:19","date_gmt":"2024-11-21T06:45:19","guid":{"rendered":"http:\/\/engineersgarag-main\/atmega-32u4-based-usb-number-pad-part-7-25\/"},"modified":"2024-11-21T05:45:52","modified_gmt":"2024-11-21T10:45:52","slug":"atmega-32u4-based-usb-number-pad-part-7-25","status":"publish","type":"post","link":"https:\/\/www.engineersgarage.com\/atmega-32u4-based-usb-number-pad-part-7-25\/","title":{"rendered":"Atmega 32u4 Based USB Number Pad (Part 7\/25)"},"content":{"rendered":"

How keyboards are made? This has been already discussed in Atmega 32u4 based Generic USB Keyboard project<\/strong><\/a>. A number pad is also a kind of keyboard having the keys for decimal digits and the basic arithmetic operations. Building from the keyboard project, a basic numeric keypad that will work with all the operating systems is designed in the following project. The keypad will have ten keys for the decimal digits and one key for multiplication, division, subtraction, addition and equals each. Each of these digits or operations has unique keycode assigned. The project utilizes 8-bit USB AVR – Atmega 32u4 as the USB controller chip to pass the keycodes to the computer in a format dictated by the USB protocol and uses AVR based Lightweight USB Framework (LUFA) as the firmware to implement the protocol itself.<\/span><\/p>\n

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

Fig. 1: Prototype of Arduino Based USB Number Keypad\u00a0<\/em><\/p>\n

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

\u2022 Ten Digit Keys (0-9)<\/p>\n

\u2022 Addition<\/p>\n

\u2022 Subtraction<\/p>\n

\u2022 Multiplication<\/p>\n

\u2022 Division<\/p>\n

\u2022 Equals<\/p>\n

This number pad can be used with any USB enabled computing device and any operating system. 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: Image demonstrating working of Arduino Based USB Number Keypad\u00a0<\/em><\/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

\"Block<\/p>\n

Fig. 3: Block Diagram of Arduino Based USB Number Keypad\u00a0<\/em><\/p>\n

CIRCUIT CONNECTIONS<\/h4>\n

The project uses Arduino Pro Micro as the USB controller chip. A set of fifteen tactile switches is connected to the port B, D, and F of the Arduino. The switches are connected to pins 1, 2, 4, 5 and 6 of the port B, 0, 1, 2, 3, 4 and 7 of Port D and 4, 5, 6 and 7 of Port F with functions assigned to them according to the following table -:<\/p>\n

\"Table<\/p>\n

Fig. 4:\u00a0Table listing Arduino pins and respective keypad functions<\/em><\/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

 <\/p>\n

HOW THE PROJECT WORKS<\/h2>\n

For configuring the controller chip to work as a Keypad controller, the \u00a0HID Class Driver for keyboard of the LUFA framework is used. 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 \u00a0of the LUFA framework.<\/p>\n

Like any HID device, when the numeric 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 numeric operations. The process of identification and configuration of any USB device with the host is called enumeration.<\/p>\n

\"Image<\/p>\n

Fig. 5:\u00a0Image showing number 0 typed from Arduino USB Keypad<\/em><\/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<\/a> 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. For this project, each key has a unique keycode which needs to be passed by the controller chip on detecting the pressing of respective button The buttons on the keypad passes the keycodes for the following keys.<\/p>\n

\"Table<\/p>\n

Fig. 6: Table listing Arduino pins and respective keypad functions and keycodes<\/em><\/p>\n

The numeric 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 numeric 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.<\/span><\/p>\n

HOW THE DEVICE WORKS<\/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 keycodes in the data input report. Check out the program code to see the modifications implemented for this numeric keypad.<\/p>\n

\"Image<\/p>\n

Fig. 7:\u00a0Image showing numerals typed from Arduino based USB Keypad<\/span><\/em><\/p>\n

PROGRAMMING GUIDE<\/h4>\n

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

\"Screenshot<\/p>\n

Fig. 8:\u00a0Screenshot of LUFA Library Folder on Windows<\/span><\/em><\/p>\n

Of these, Keyboard.h, Keyboard.c and Makefile needs to be modified for this project.\u00a0The 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.<\/p>\n

Modifying Keyboard.h<\/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 – :<\/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)<\/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()<\/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, D and F 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 int main(void)<\/div>\n
{<\/div>\n
\u00a0 \u00a0 SetupHardware();<\/div>\n
<\/div>\n
\u00a0 \u00a0 DDRB = 0x00;<\/div>\n
\u00a0 \u00a0 DDRD = 0x00;<\/div>\n
\u00a0 \u00a0 DDRF = 0x00;<\/div>\n
\u00a0 \u00a0 PORTB = 0xff;<\/div>\n
\u00a0 \u00a0 PORTD = 0xff;<\/div>\n
\u00a0 \u00a0 PORTF = 0xff;<\/div>\n
\u00a0 \u00a0 \/\/LEDs_SetAllLEDs(LEDMASK_USB_NOTREADY);<\/div>\n
\u00a0 \u00a0 GlobalInterruptEnable();<\/div>\n
<\/div>\n
\u00a0 \u00a0 for (;;)<\/div>\n
\u00a0 \u00a0 {<\/div>\n
\u00a0 \u00a0 \u00a0 HID_Device_USBTask(&Keyboard_HID_Interface);<\/div>\n
\u00a0 \u00a0 \u00a0 USB_USBTask();<\/div>\n
\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).<\/p>\n

For creating Keyboard Data Input report to pass the 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 of LUFA library<\/em><\/p>\n

The numeric keypad is using tactile switches to get the hint of keycode that needs to be passed. Therefore, LOW bit at each button is detected and the corresponding keycode 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
USB_KeyboardReport_Data_t* KeyboardReport = (USB_KeyboardReport_Data_t*)ReportData;<\/div>\n
<\/div>\n
<\/div>\n
uint8_t UsedKeyCodes = 0;<\/div>\n
<\/div>\n
\u00a0 if(!(PIND & _BV(PD3))) {<\/div>\n
\/\/ add keycode for numeric 0 in the report<\/div>\n
KeyboardReport->KeyCode[UsedKeyCodes++] = HID_KEYBOARD_SC_KEYPAD_0_AND_INSERT;<\/div>\n
}<\/div>\n
else if(!(PIND & _BV(PD2))) {<\/div>\n
\/\/ add keycode for numeric 1 in the report<\/div>\n
KeyboardReport->KeyCode[UsedKeyCodes++] = HID_KEYBOARD_SC_KEYPAD_1_AND_END;<\/div>\n
}<\/div>\n
else if(!(PIND & _BV(PD1))) {<\/div>\n
\/\/ add keycode for numeric 2 in the report<\/div>\n
KeyboardReport->KeyCode[UsedKeyCodes++] = HID_KEYBOARD_SC_KEYPAD_2_AND_DOWN_ARROW;<\/div>\n
}<\/div>\n
else if(!(PIND & _BV(PD0))) {<\/div>\n
\/\/ add keycode for numeric 3 in the report<\/div>\n
KeyboardReport->KeyCode[UsedKeyCodes++] = HID_KEYBOARD_SC_KEYPAD_3_AND_PAGE_DOWN;<\/div>\n
}<\/div>\n
else if(!(PIND & _BV(PD4))) {<\/div>\n
\/\/ add keycode for numeric 4 in the report<\/div>\n
KeyboardReport->KeyCode[UsedKeyCodes++] = HID_KEYBOARD_SC_KEYPAD_4_AND_LEFT_ARROW;<\/div>\n
}<\/div>\n
else if(!(PIND & _BV(PD7))) {<\/div>\n
\/\/ add keycode for numeric 5 in the report<\/div>\n
KeyboardReport->KeyCode[UsedKeyCodes++] = HID_KEYBOARD_SC_KEYPAD_5;<\/div>\n
}<\/div>\n
else if(!(PINB & _BV(PB4))) {<\/div>\n
\/\/ add keycode for numeric 6 in the report<\/div>\n
KeyboardReport->KeyCode[UsedKeyCodes++] = HID_KEYBOARD_SC_KEYPAD_6_AND_RIGHT_ARROW;<\/div>\n
}<\/div>\n
else if(!(PINB & _BV(PB5))) {<\/div>\n
\/\/ add keycode for numeric 7 in the report<\/div>\n
KeyboardReport->KeyCode[UsedKeyCodes++] = HID_KEYBOARD_SC_KEYPAD_7_AND_HOME;<\/div>\n
}<\/div>\n
else if(!(PINB & _BV(PB6))) {<\/div>\n
\/\/ add keycode for numeric 8 in the report<\/div>\n
KeyboardReport->KeyCode[UsedKeyCodes++] = HID_KEYBOARD_SC_KEYPAD_8_AND_UP_ARROW;<\/div>\n
}<\/div>\n
else if(!(PINB & _BV(PB2))) {<\/div>\n
\/\/ add keycode for numeric 9 in the report<\/div>\n
KeyboardReport->KeyCode[UsedKeyCodes++] = HID_KEYBOARD_SC_KEYPAD_9_AND_PAGE_UP;<\/div>\n
}<\/div>\n
else if(!(PINB & _BV(PB1))) {<\/div>\n
\/\/ add keycode for dot in the report<\/div>\n
KeyboardReport->KeyCode[UsedKeyCodes++] = HID_KEYBOARD_SC_KEYPAD_DOT_AND_DELETE;<\/div>\n
}<\/div>\n
else if(!(PINF & _BV(PF7))) {<\/div>\n
\/\/ add keycode for – in the report<\/div>\n
KeyboardReport->KeyCode[UsedKeyCodes++] = HID_KEYBOARD_SC_KEYPAD_MINUS;<\/div>\n
}<\/div>\n
else if(!(PINF & _BV(PF6))) {<\/div>\n
\/\/ add keycode for + in the report<\/div>\n
KeyboardReport->KeyCode[UsedKeyCodes++] = HID_KEYBOARD_SC_KEYPAD_PLUS;<\/div>\n
}<\/div>\n
else if(!(PINF & _BV(PF5))) {<\/div>\n
\/\/ add keycode for del in the report<\/div>\n
KeyboardReport->KeyCode[UsedKeyCodes++] = HID_KEYBOARD_SC_SLASH;<\/div>\n
}<\/div>\n
else if(!(PINF & _BV(PF4))) {<\/div>\n
\/\/ add keycode for enter in the report<\/div>\n
KeyboardReport->KeyCode[UsedKeyCodes++] = HID_KEYBOARD_SC_KEYPAD_ENTER;<\/div>\n
}<\/div>\n
<\/div>\n
<\/div>\n
*ReportSize = sizeof(USB_KeyboardReport_Data_t);<\/div>\n
return false;<\/div>\n
}<\/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 numeric keys are used (defined in HIDCommonClass.h, header file located in \u00a0LUFA-Source-FolderLUFADriversUSBClassCommon folder).<\/p>\n

\"Table<\/p>\n

Fig. 9:\u00a0Table listing keys and respective constants used in LUFA<\/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<\/span><\/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 numeric 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.<\/p>\n

BURNING HEX CODE<\/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.<\/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. Use the numeric keypad similar to number pad of any generic USB keyboard.<\/p>\n

In the next project – Atmega 32u4 based Multimedia Keypad<\/strong><\/a>, learn how to make a keypad to control multimedia operations.<\/div>\n","protected":false},"excerpt":{"rendered":"

How keyboards are made? This has been already discussed in Atmega 32u4 based Generic USB Keyboard project. A number pad is also a kind of keyboard having the keys for decimal digits and the basic arithmetic operations. Building from the keyboard project, a basic numeric keypad that will work with all the operating systems is designed in the following project. The keypad will have ten keys for the decimal digits and one key for multiplication, division, subtraction, addition and equals each. Each of these digits or operations has unique keycode assigned. The project utilizes 8-bit USB AVR – Atmega 32u4 as the USB controller chip to pass the keycodes to the computer in a format dictated by the USB protocol and uses AVR based Lightweight USB Framework (LUFA) as the firmware to implement the protocol itself.<\/p>\n","protected":false},"author":311,"featured_media":51419,"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 USB Number Pad (Part 7\/25)<\/title>\n<meta name=\"description\" content=\"We will design a basic numeric keypad which has ten keys for the decimal digits and one key for multiplication, division, subtraction etc.\" \/>\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-usb-number-pad-part-7-25\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Atmega 32u4 Based USB Number Pad (Part 7\/25)\" \/>\n<meta property=\"og:description\" content=\"We will design a basic numeric keypad which has ten keys for the decimal digits and one key for multiplication, division, subtraction etc.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.engineersgarage.com\/atmega-32u4-based-usb-number-pad-part-7-25\/\" \/>\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\" content=\"https:\/\/www.engineersgarage.com\/wp-content\/uploads\/2019\/07\/Prototype-Arduino-Based-USB-Number-Keypad-.jpg\" \/>\n\t<meta property=\"og:image:width\" content=\"600\" \/>\n\t<meta property=\"og:image:height\" content=\"338\" \/>\n\t<meta property=\"og:image:type\" content=\"image\/jpeg\" \/>\n<meta name=\"author\" content=\"Amanpreet Singh\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:creator\" content=\"@EngineersGarage\" \/>\n<meta name=\"twitter:site\" content=\"@EngineersGarage\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"Amanpreet Singh\" \/>\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"14 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"Article\",\"@id\":\"https:\/\/www.engineersgarage.com\/atmega-32u4-based-usb-number-pad-part-7-25\/#article\",\"isPartOf\":{\"@id\":\"https:\/\/www.engineersgarage.com\/atmega-32u4-based-usb-number-pad-part-7-25\/\"},\"author\":{\"name\":\"Amanpreet Singh\",\"@id\":\"https:\/\/www.engineersgarage.com\/#\/schema\/person\/526929dd58916ffb049da3e9adae8ead\"},\"headline\":\"Atmega 32u4 Based USB Number Pad (Part 7\/25)\",\"datePublished\":\"2024-11-21T06:45:19+00:00\",\"dateModified\":\"2024-11-21T10:45:52+00:00\",\"mainEntityOfPage\":{\"@id\":\"https:\/\/www.engineersgarage.com\/atmega-32u4-based-usb-number-pad-part-7-25\/\"},\"wordCount\":2824,\"commentCount\":0,\"publisher\":{\"@id\":\"https:\/\/www.engineersgarage.com\/#organization\"},\"image\":{\"@id\":\"https:\/\/www.engineersgarage.com\/atmega-32u4-based-usb-number-pad-part-7-25\/#primaryimage\"},\"thumbnailUrl\":\"https:\/\/www.engineersgarage.com\/wp-content\/uploads\/2019\/07\/Prototype-Arduino-Based-USB-Number-Keypad-.jpg\",\"articleSection\":[\"Electronic Projects\"],\"inLanguage\":\"en-US\",\"potentialAction\":[{\"@type\":\"CommentAction\",\"name\":\"Comment\",\"target\":[\"https:\/\/www.engineersgarage.com\/atmega-32u4-based-usb-number-pad-part-7-25\/#respond\"]}]},{\"@type\":\"WebPage\",\"@id\":\"https:\/\/www.engineersgarage.com\/atmega-32u4-based-usb-number-pad-part-7-25\/\",\"url\":\"https:\/\/www.engineersgarage.com\/atmega-32u4-based-usb-number-pad-part-7-25\/\",\"name\":\"Atmega 32u4 Based USB Number Pad (Part 7\/25)\",\"isPartOf\":{\"@id\":\"https:\/\/www.engineersgarage.com\/#website\"},\"primaryImageOfPage\":{\"@id\":\"https:\/\/www.engineersgarage.com\/atmega-32u4-based-usb-number-pad-part-7-25\/#primaryimage\"},\"image\":{\"@id\":\"https:\/\/www.engineersgarage.com\/atmega-32u4-based-usb-number-pad-part-7-25\/#primaryimage\"},\"thumbnailUrl\":\"https:\/\/www.engineersgarage.com\/wp-content\/uploads\/2019\/07\/Prototype-Arduino-Based-USB-Number-Keypad-.jpg\",\"datePublished\":\"2024-11-21T06:45:19+00:00\",\"dateModified\":\"2024-11-21T10:45:52+00:00\",\"description\":\"We will design a basic numeric keypad which has ten keys for the decimal digits and one key for multiplication, division, subtraction etc.\",\"breadcrumb\":{\"@id\":\"https:\/\/www.engineersgarage.com\/atmega-32u4-based-usb-number-pad-part-7-25\/#breadcrumb\"},\"inLanguage\":\"en-US\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\/\/www.engineersgarage.com\/atmega-32u4-based-usb-number-pad-part-7-25\/\"]}]},{\"@type\":\"ImageObject\",\"inLanguage\":\"en-US\",\"@id\":\"https:\/\/www.engineersgarage.com\/atmega-32u4-based-usb-number-pad-part-7-25\/#primaryimage\",\"url\":\"https:\/\/www.engineersgarage.com\/wp-content\/uploads\/2019\/07\/Prototype-Arduino-Based-USB-Number-Keypad-.jpg\",\"contentUrl\":\"https:\/\/www.engineersgarage.com\/wp-content\/uploads\/2019\/07\/Prototype-Arduino-Based-USB-Number-Keypad-.jpg\",\"width\":600,\"height\":338,\"caption\":\"\"},{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\/\/www.engineersgarage.com\/atmega-32u4-based-usb-number-pad-part-7-25\/#breadcrumb\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\/\/www.engineersgarage.com\/\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"Atmega 32u4 Based USB Number Pad (Part 7\/25)\"}]},{\"@type\":\"WebSite\",\"@id\":\"https:\/\/www.engineersgarage.com\/#website\",\"url\":\"https:\/\/www.engineersgarage.com\/\",\"name\":\"Engineers Garage\",\"description\":\"Electronic Projects, Electrical Engineering Resources, Makers Articles and Product News\",\"publisher\":{\"@id\":\"https:\/\/www.engineersgarage.com\/#organization\"},\"potentialAction\":[{\"@type\":\"SearchAction\",\"target\":{\"@type\":\"EntryPoint\",\"urlTemplate\":\"https:\/\/www.engineersgarage.com\/?s={search_term_string}\"},\"query-input\":{\"@type\":\"PropertyValueSpecification\",\"valueRequired\":true,\"valueName\":\"search_term_string\"}}],\"inLanguage\":\"en-US\"},{\"@type\":\"Organization\",\"@id\":\"https:\/\/www.engineersgarage.com\/#organization\",\"name\":\"Engineer's Garage - WTWH Media\",\"url\":\"https:\/\/www.engineersgarage.com\/\",\"logo\":{\"@type\":\"ImageObject\",\"inLanguage\":\"en-US\",\"@id\":\"https:\/\/www.engineersgarage.com\/#\/schema\/logo\/image\/\",\"url\":\"https:\/\/www.engineersgarage.com\/wp-content\/uploads\/2019\/08\/EGlogo.png\",\"contentUrl\":\"https:\/\/www.engineersgarage.com\/wp-content\/uploads\/2019\/08\/EGlogo.png\",\"width\":372,\"height\":52,\"caption\":\"Engineer's Garage - WTWH Media\"},\"image\":{\"@id\":\"https:\/\/www.engineersgarage.com\/#\/schema\/logo\/image\/\"},\"sameAs\":[\"https:\/\/www.facebook.com\/engineersgarage\",\"https:\/\/x.com\/EngineersGarage\",\"https:\/\/www.youtube.com\/channel\/UC0VITh11JSYk-UW7toLebUw\"]},{\"@type\":\"Person\",\"@id\":\"https:\/\/www.engineersgarage.com\/#\/schema\/person\/526929dd58916ffb049da3e9adae8ead\",\"name\":\"Amanpreet Singh\",\"image\":{\"@type\":\"ImageObject\",\"inLanguage\":\"en-US\",\"@id\":\"https:\/\/www.engineersgarage.com\/#\/schema\/person\/image\/\",\"url\":\"https:\/\/secure.gravatar.com\/avatar\/ae10b6a902c38b371923411a43a9bfe57a88c4fdcc00744c0ece299e5401ae17?s=96&r=g\",\"contentUrl\":\"https:\/\/secure.gravatar.com\/avatar\/ae10b6a902c38b371923411a43a9bfe57a88c4fdcc00744c0ece299e5401ae17?s=96&r=g\",\"caption\":\"Amanpreet Singh\"},\"url\":\"https:\/\/www.engineersgarage.com\/author\/asingh\/\"}]}<\/script>\n<!-- \/ Yoast SEO Premium plugin. -->","yoast_head_json":{"title":"Atmega 32u4 Based USB Number Pad (Part 7\/25)","description":"We will design a basic numeric keypad which has ten keys for the decimal digits and one key for multiplication, division, subtraction etc.","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/www.engineersgarage.com\/atmega-32u4-based-usb-number-pad-part-7-25\/","og_locale":"en_US","og_type":"article","og_title":"Atmega 32u4 Based USB Number Pad (Part 7\/25)","og_description":"We will design a basic numeric keypad which has ten keys for the decimal digits and one key for multiplication, division, subtraction etc.","og_url":"https:\/\/www.engineersgarage.com\/atmega-32u4-based-usb-number-pad-part-7-25\/","og_site_name":"Engineers Garage","article_publisher":"https:\/\/www.facebook.com\/engineersgarage","og_image":[{"width":600,"height":338,"url":"https:\/\/www.engineersgarage.com\/wp-content\/uploads\/2019\/07\/Prototype-Arduino-Based-USB-Number-Keypad-.jpg","type":"image\/jpeg"}],"author":"Amanpreet Singh","twitter_card":"summary_large_image","twitter_creator":"@EngineersGarage","twitter_site":"@EngineersGarage","twitter_misc":{"Written by":"Amanpreet Singh","Est. reading time":"14 minutes"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"Article","@id":"https:\/\/www.engineersgarage.com\/atmega-32u4-based-usb-number-pad-part-7-25\/#article","isPartOf":{"@id":"https:\/\/www.engineersgarage.com\/atmega-32u4-based-usb-number-pad-part-7-25\/"},"author":{"name":"Amanpreet Singh","@id":"https:\/\/www.engineersgarage.com\/#\/schema\/person\/526929dd58916ffb049da3e9adae8ead"},"headline":"Atmega 32u4 Based USB Number Pad (Part 7\/25)","datePublished":"2024-11-21T06:45:19+00:00","dateModified":"2024-11-21T10:45:52+00:00","mainEntityOfPage":{"@id":"https:\/\/www.engineersgarage.com\/atmega-32u4-based-usb-number-pad-part-7-25\/"},"wordCount":2824,"commentCount":0,"publisher":{"@id":"https:\/\/www.engineersgarage.com\/#organization"},"image":{"@id":"https:\/\/www.engineersgarage.com\/atmega-32u4-based-usb-number-pad-part-7-25\/#primaryimage"},"thumbnailUrl":"https:\/\/www.engineersgarage.com\/wp-content\/uploads\/2019\/07\/Prototype-Arduino-Based-USB-Number-Keypad-.jpg","articleSection":["Electronic Projects"],"inLanguage":"en-US","potentialAction":[{"@type":"CommentAction","name":"Comment","target":["https:\/\/www.engineersgarage.com\/atmega-32u4-based-usb-number-pad-part-7-25\/#respond"]}]},{"@type":"WebPage","@id":"https:\/\/www.engineersgarage.com\/atmega-32u4-based-usb-number-pad-part-7-25\/","url":"https:\/\/www.engineersgarage.com\/atmega-32u4-based-usb-number-pad-part-7-25\/","name":"Atmega 32u4 Based USB Number Pad (Part 7\/25)","isPartOf":{"@id":"https:\/\/www.engineersgarage.com\/#website"},"primaryImageOfPage":{"@id":"https:\/\/www.engineersgarage.com\/atmega-32u4-based-usb-number-pad-part-7-25\/#primaryimage"},"image":{"@id":"https:\/\/www.engineersgarage.com\/atmega-32u4-based-usb-number-pad-part-7-25\/#primaryimage"},"thumbnailUrl":"https:\/\/www.engineersgarage.com\/wp-content\/uploads\/2019\/07\/Prototype-Arduino-Based-USB-Number-Keypad-.jpg","datePublished":"2024-11-21T06:45:19+00:00","dateModified":"2024-11-21T10:45:52+00:00","description":"We will design a basic numeric keypad which has ten keys for the decimal digits and one key for multiplication, division, subtraction etc.","breadcrumb":{"@id":"https:\/\/www.engineersgarage.com\/atmega-32u4-based-usb-number-pad-part-7-25\/#breadcrumb"},"inLanguage":"en-US","potentialAction":[{"@type":"ReadAction","target":["https:\/\/www.engineersgarage.com\/atmega-32u4-based-usb-number-pad-part-7-25\/"]}]},{"@type":"ImageObject","inLanguage":"en-US","@id":"https:\/\/www.engineersgarage.com\/atmega-32u4-based-usb-number-pad-part-7-25\/#primaryimage","url":"https:\/\/www.engineersgarage.com\/wp-content\/uploads\/2019\/07\/Prototype-Arduino-Based-USB-Number-Keypad-.jpg","contentUrl":"https:\/\/www.engineersgarage.com\/wp-content\/uploads\/2019\/07\/Prototype-Arduino-Based-USB-Number-Keypad-.jpg","width":600,"height":338,"caption":""},{"@type":"BreadcrumbList","@id":"https:\/\/www.engineersgarage.com\/atmega-32u4-based-usb-number-pad-part-7-25\/#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https:\/\/www.engineersgarage.com\/"},{"@type":"ListItem","position":2,"name":"Atmega 32u4 Based USB Number Pad (Part 7\/25)"}]},{"@type":"WebSite","@id":"https:\/\/www.engineersgarage.com\/#website","url":"https:\/\/www.engineersgarage.com\/","name":"Engineers Garage","description":"Electronic Projects, Electrical Engineering Resources, Makers Articles and Product News","publisher":{"@id":"https:\/\/www.engineersgarage.com\/#organization"},"potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https:\/\/www.engineersgarage.com\/?s={search_term_string}"},"query-input":{"@type":"PropertyValueSpecification","valueRequired":true,"valueName":"search_term_string"}}],"inLanguage":"en-US"},{"@type":"Organization","@id":"https:\/\/www.engineersgarage.com\/#organization","name":"Engineer's Garage - WTWH Media","url":"https:\/\/www.engineersgarage.com\/","logo":{"@type":"ImageObject","inLanguage":"en-US","@id":"https:\/\/www.engineersgarage.com\/#\/schema\/logo\/image\/","url":"https:\/\/www.engineersgarage.com\/wp-content\/uploads\/2019\/08\/EGlogo.png","contentUrl":"https:\/\/www.engineersgarage.com\/wp-content\/uploads\/2019\/08\/EGlogo.png","width":372,"height":52,"caption":"Engineer's Garage - WTWH Media"},"image":{"@id":"https:\/\/www.engineersgarage.com\/#\/schema\/logo\/image\/"},"sameAs":["https:\/\/www.facebook.com\/engineersgarage","https:\/\/x.com\/EngineersGarage","https:\/\/www.youtube.com\/channel\/UC0VITh11JSYk-UW7toLebUw"]},{"@type":"Person","@id":"https:\/\/www.engineersgarage.com\/#\/schema\/person\/526929dd58916ffb049da3e9adae8ead","name":"Amanpreet Singh","image":{"@type":"ImageObject","inLanguage":"en-US","@id":"https:\/\/www.engineersgarage.com\/#\/schema\/person\/image\/","url":"https:\/\/secure.gravatar.com\/avatar\/ae10b6a902c38b371923411a43a9bfe57a88c4fdcc00744c0ece299e5401ae17?s=96&r=g","contentUrl":"https:\/\/secure.gravatar.com\/avatar\/ae10b6a902c38b371923411a43a9bfe57a88c4fdcc00744c0ece299e5401ae17?s=96&r=g","caption":"Amanpreet Singh"},"url":"https:\/\/www.engineersgarage.com\/author\/asingh\/"}]}},"featured_image_src":"https:\/\/www.engineersgarage.com\/wp-content\/uploads\/2019\/07\/Prototype-Arduino-Based-USB-Number-Keypad-.jpg","featured_image_src_square":"https:\/\/www.engineersgarage.com\/wp-content\/uploads\/2019\/07\/Prototype-Arduino-Based-USB-Number-Keypad-.jpg","author_info":{"display_name":"Amanpreet Singh","author_link":"https:\/\/www.engineersgarage.com\/author\/asingh\/"},"_links":{"self":[{"href":"https:\/\/www.engineersgarage.com\/wp-json\/wp\/v2\/posts\/13417","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.engineersgarage.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.engineersgarage.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.engineersgarage.com\/wp-json\/wp\/v2\/users\/311"}],"replies":[{"embeddable":true,"href":"https:\/\/www.engineersgarage.com\/wp-json\/wp\/v2\/comments?post=13417"}],"version-history":[{"count":0,"href":"https:\/\/www.engineersgarage.com\/wp-json\/wp\/v2\/posts\/13417\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.engineersgarage.com\/wp-json\/wp\/v2\/media\/51419"}],"wp:attachment":[{"href":"https:\/\/www.engineersgarage.com\/wp-json\/wp\/v2\/media?parent=13417"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.engineersgarage.com\/wp-json\/wp\/v2\/categories?post=13417"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.engineersgarage.com\/wp-json\/wp\/v2\/tags?post=13417"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}