USB Keyboard & Barcode Decoder - Serial Output

The product is a USB Host which accepts any USB Keyboard at its USB port and decodes the button presses. The data is output as serial TTL UART at 9600 baud rate for easy interfacing with various applications. The output is suitable for 3V or 5V level microcontroller applications.

Features

• Easy to Use with variety of keyboard types (including wireless keyboard but excluding gaming type composite keyboard)
• Keyboard status LEDs supported
• Multicolor Status LEDs for Error, Activity and Power
• Simple output can work with any type of microcontroller
• Also accepts Wireless Keyboard also by inserting its RF receiver into USB host port
• Also accepts simple 17 key USB Keypad
• All keys including multimedia,windows keys supported
• Full support for Caps Lock, Num Lock, Alt+CTRL+<Key>

Various Keyboard with USB Interface Supported

Apart from standard full size keyboard, The decoder also supports custom made or small numeric keypads.

Pinouts

• TX-OUT - Transmit output, usually goes to your microcontroller receive pin RXD
• +5V - Regulated +5V power input
• GND - Common Ground
• DET - Idle Low, Goes High when keyboard activity happens. Goes low again after data transfer at TX pin is finished. Useful for input to external microcontroller for polling or interrupt to process the data from board.

Note: RX-IN pin and other pins are not used in this application, leave it floating. Below you can see, we have provided holes for mounting header of 2.54mm pitch if required.

Status LEDs

• Board has three LEDs
• PWR - Green LED indicate that board is getting power
• STS - Yellow LED indicate any keyboard activity
• ERR - Red LED indicate any error like keyboard not detected

Output Data Format

• 9600 bps - 8 - N - 1 (No parity)
• Output voltage level 3.3V TTL UART (Can also connect to 5V operated MCU RX pin directly.)
• Data is sent out only when any button is pressed.

There can be three type of key types by user

Case#1: Simple ASCII keys - Single Byte Output

The output is simple ASCII values for each key as shown below. If Caps lock is ON, all values are capital and if Shift+key is pressed the character is upper case just like in PC. For enter key, its CR+LF type two byte output like shown below, else all output keys are of single byte.

Case#2: ALT+<KEY> or CTRL+<KEY> or Special Keys

See below on pressing
CTRL+C gives out 0x02 and 0x043 where 0x02 is code for Control Key followed by Key value 0x43 for ASCII 'C'.
ALT+C gives out 0x01 and 0x43 where 0x01 is code fr Alter Key followed by Key value 0x43 for ASCII 'C'.
If any special keys except ASCII Key on keyboard like arrow key is pressed it gives out value as 0x00 following by key value like below arrow key value of 0x52. If same arrow key was combined with CTRL then the output would be 0x02+0x52 or with ALT would be 0x01+0x52.

Case #3 CTRL+ALT+DEL - Key Combinations

Decoder supports 3 key combination also just like windows. You can combine the third key with any other key on keyboard. So output would be 0x01+0x02+<KEY CODE>, Also windows GUI key is supported, it always gives out 0x03 value which cannot be combined with any other key.