Turning Ideas Into Reality ABCircuits www.abcircuits.com POB 123 New Hill NC 27562 (919) 290-7104 KBDGRAY IC Serial output encoder for Grayhill and other keyboards up to 16 switches General Description The KBDGRAY IC is designed to provide a serial ASCII output encoder for Grayhill 96 series and other keyboards up to 16 keys. The KBDGRAY IC contains all the logic necessary to encode a SPST keyboard switch array up to 4 by 4 in size and provide a serial ASCII output. The output is standard asynchronous format, using 8 bits, 1 stop and no parity at 9600 BPS. Other formats and encoding are available, contact the factory. The array can be a 4 x 4 array, but smaller arrays such as a 3 x 4 array or any smaller size may be used. The KBDGRAY IC handles debouncing and encodes the keys with no external parts. All timing is internally generated. No external diodes are required in the array to prevent key ghosting in a two key rollover situation. A .1 uF bypass capacitor is suggested across the VDD and VSS pins. The part uses the standard 20 pin .3 inch width SOIC package. Features • Asynchronous serial output. • • • • • • • • • • • • • ASCII 0-9, #, *, and A-D (on 16 key keypads) Fully encodes a key switch array. (up to 4 x 4) No external parts required. Low power consumption 5 mA typical. Supply voltage 2.4 to 5.25 volts. All timing internally generated. Applications • Data Entry • Security Alarms • Handheld devices • Machine Control • Numeric Entry • Telephones • Computers • Controls • Gaming 2 Key rollover. On chip row input resistors. Internal key bounce elimination. TTL and CMOS compatible outputs. Part is in full production. SOIC and DIP 20 Pin Package. ROHS Compliant Low EMI Part Number 74C922-SO Copyright © 2014 ABCircuits. Revised September 2014 Page 1 of 6 Turning Ideas Into Reality ABCircuits www.abcircuits.com POB 123 New Hill NC 27562 (919) 290-7104 Example Circuits VCC VCC KBDGRAY 1 2 3 4 5 6 7 8 9 10 ROWY1 ROWY2 ROWY3 ROWY4 NC NC NC COLX4 COLX3 VSS VDD NC NC NC NC NC NC SOUT COLX1 COLX2 C5 .1 20 19 18 17 16 15 14 13 12 11 1 3 C6 .1 4 5 11 10 KEYPAD 2 3 A 2 2 4 5 6 B 3 3 7 8 9 C 4 4 * 0 # D 7 8 9 V+ +5 C7 .1 2 C1C2+ V- 6 C8 .1 C2T1in T1out T2in T2out R1out R2out GND 1 C1+ U2 SEE NOTES R1in R2in RS232 DB9S J1 1 2 3 4 5 6 7 8 9 8 14 7 13 8 TXD GND 15 1 6 12 1 5 PINS1X8 VCC 16 16 KEY RS-232 ENCODED KEYBOARD U2= MAX232 FOR 5V RS232 U2= MAX3232 FOR 3V RS232 5 6 7 8 12 KEY RS-485 ENCODED KEYBOARD VCC VCC KBDGRAY 1 2 3 4 5 6 7 8 9 10 ROWY1 ROWY2 ROWY3 ROWY4 NC NC NC COLX4 COLX3 VSS VDD NC NC NC NC NC NC SOUT COLX1 COLX2 20 19 18 17 16 15 14 13 12 11 U2 1 VCC 2 3 4 RO VCC -RE -DO/-RI DE DO / RI DI GND 8 7 6 RS485 OUT 5 KEYPAD PINS1X7 2 3 2 4 5 6 3 3 7 8 9 4 4 * 0 # 7 2 1 6 1 5 1 U2 75176 FOR 5V U2 MAX3485 FOR 3.3V 5 6 7 Part Number KBDGRAY Copyright © 2014 ABCircuits. Revised September 2014 Page 2 of 6 Turning Ideas Into Reality ABCircuits www.abcircuits.com POB 123 New Hill NC 27562 (919) 290-7104 16 KEY ETHERNET KEYBOARD +3.3 +3.3 KBDGRAY ROWY1 ROWY2 ROWY3 ROWY4 NC NC NC COLX4 COLX3 VSS VDD NC NC NC NC NC NC SOUT COLX1 COLX2 20 19 18 17 16 15 14 13 12 11 LANTRONIX XPORT 1 2 3 4 5 6 7 8 KEYPAD 1 1 1 2 3 A 2 2 4 5 6 B 3 3 7 8 9 C 4 4 * 0 # D 5 6 7 8 PINS1X8 GND +3.3 -POR OUT IN CP1 CP2 CP3 5 6 7 8 Connection Diagram KBDGRAY 1 2 3 4 5 6 7 8 9 10 ROWY1 ROWY2 ROWY3 ROWY4 NC NC NC COLX4 COLX3 VSS VDD NC NC NC NC NC NC SOUT COLX1 COLX2 20 19 18 17 16 15 14 13 12 11 Pin Description Pin # 1 2 3 4 5 6 7 8 9 10 Description Row Y1 Row Y2 Row Y3 Row Y4 NC NC NC Col X4 Col X3 VSS Pin # 20 19 18 17 16 15 14 13 12 21 Description VDD NC NC NC NC NC NC SOUT Col X1 Col X2 Col X1 – Col X4 These pins are open drain column driver outputs to the key matrix. Part Number KBDGRAY Copyright © 2014 ABCircuits. Revised September 2014 Page 3 of 6 ETHERNET 1 2 3 4 5 6 7 8 9 10 Turning Ideas Into Reality ABCircuits www.abcircuits.com POB 123 New Hill NC 27562 (919) 290-7104 Row Y1 – Row Y4 These pins are the row inputs from the key matrix. These inputs have 5.6K (nominal) pull up resistors on chip. SOUT This is the serial output pin. It may be tied directly to the UART receiver input of your UART or microprocessor; to a RS -232 driver such as the MAX232; a standard RS485 driver such as the 75176 or an Ethernet interface such as the Lantronix Xport. This pin is high in the idle state, the output format is 8 bits, 1 stop, no parity at 9600 BPS. Other output formats and baud rates are available, please contact the factory for information. VSS Connect to system ground. VDD Connect to supply voltage of 2.4 to 5 volts. A .1 uF decoupling capacitor to ground is recommended. NOTES: No connection is required to the NC pins. Pins 5 and 15 must be left unconnected. Truth Table Note: To achieve the correct output to match the keys on the Grayhill keyboard, wiring to keyboard must be as shown on the example circuits. On the Grayhill 12 key keyboards, ColX4 is not used. ROWY1 ROWY1 ROWY1 ROWY1 ROWY2 ROWY2 ROWY2 ROWY2 ROWY3 ROWY3 ROWY3 ROWY3 ROWY4 ROWY4 ROWY4 ROWY4 COLX1 X COLX2 COLX3 COLX4 X X X X X X X X X X X X X X X ASCII OUT * 0 # D 7 8 9 C 4 5 6 B 1 2 3 A HEX 2A 30 23 44 37 38 39 43 34 35 36 42 31 32 33 41 Absolute Maximum Ratings Symbol Description Tstg Ta V dd V io Imio ESD Storage Temperature Operating Temperature LU Latch up current V dd - V ss Voltage Input Voltage Maximum current into any pin Electrostatic Discharge Voltage Min -55 -40 -0.5 Vss - 0.5 -25 2000 Typical Max Units 25 +100 +85 +6.0 ºC ºC V V mA V V dd +0.5 +50 200 Notes Human Body Model ESD mA Part Number KBDGRAY Copyright © 2014 ABCircuits. Revised September 2014 Page 4 of 6 Turning Ideas Into Reality ABCircuits www.abcircuits.com POB 123 New Hill NC 27562 (919) 290-7104 DC Electrical Characteristics Symbol Description V dd Idd V oh V ol V ih V il Ioh Iol Cio Iil Rpu Supply Voltage Supply Current High Output Level Low Output Voltage Input High Level Input Low Level High Level Source Current Low Level Sink Current Capacitive load Input leakage Pull Up Resistors On Row Inputs Min Typical Max Units 5 5.25 8 V mA V V V V mA mA pF nA k? 2.4 V dd - 1.0 0.75 2.1 4 3.5 1 5.6 0.8 10 25 10 8 Notes Note 1 Ioh=10 mA Iol=25 mA Note 1: Vdd=5VDC, all inputs and outputs open Theory Of Operation The KBDGRAY IC is a custom programmed microprocessor designed to encode keyboards and provide a serial output. The open drain COLX pins are pulsed low one at a time, and the ROWY pins are sampled to check for key switch closures. If a key is detected, scanning stops until the key is released. The pressed key is encoded to ASCII and transmitted in standard asynchronous format on the SOUT key. The key is transmitted using 8 data bits, 1 stop bit and no parity. Baud rate is 9600 BPS. When the key is released scanning continues. Part Number KBDGRAY Copyright © 2014 ABCircuits. Revised September 2014 Page 5 of 6 Turning Ideas Into Reality ABCircuits www.abcircuits.com POB 123 New Hill NC 27562 (919) 290-7104 Physical Dimensions – 20 Pin DIP (-DIP Suffix) Physical Dimensions – 20 Pin SOIC Close but not quite? Our products are software based, we can modify existing parts to fit your needs at a minimal cost or create new parts designed to your specifications. Email us and we can make a chip for you! For the latest version of this spec sheet, visit www.abcircuits.com Design Services Available We can quickly turn your idea into a chip, a pc board, or a finished product. Contact us with your needs and specifications. Part Number KBDGRAY Copyright © 2014 ABCircuits. Revised September 2014 Page 6 of 6