EDE1144SO 查看數據表（PDF） - Unspecified
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EDE1144SO Datasheet PDF : 7 Pages
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EDE1144 Keypad Encoder IC
SERIAL DATA CONNECTION
To receive keypress data serially from the EDE1144, two options exist. The first (typically used
with a host microcontroller having an onboard hardware UART) is to simply connect the XMIT
(Pin 1) line to the host microcontroller's serial data input. Each time a key is pressed (or the
autorepeat loop cycles) one byte will be transmitted, corresponding to the values shown in Table
One. The host microcontroller's hardware UART's 'Receive Buffer Full' flag can be polled to
monitor for newly received serial data; alternately the host microcontroller can be configured to
generate an interrupt when a new byte is received by the UART.
The second method of receiving serial data from the EDE1144 involves the use of the Data Valid
signal (Pin 17). This pin can be polled by the host microcontroller, or connected to an external
interrupt input. Once this pin transitions to its active level (low), the EDE1144 pauses 45mS
(while the keybeep signal is generated) before the start bit and remaining data bits are sent,
during which the host microcontroller can finish what it is doing and enter the serial receive
routine, holding there until it detects the EDE1144's start bit. This method is ideal for BASIC
Stamps™ and other devices using a 'software' (a non-hardware, or 'bit-bang') UART.
SMALLER KEYPADS
The EDE1144 can be used with keypads smaller than 4 rows by 4 columns, such as 3 rows by
four columns, 1 row by 4 columns, etc. Simply connect the keypad as shown in Figure Two,
starting with Row 0 and Column 0, connecting as many rows and columns as your keypad has.
Be certain to use the 330 Ohm resistor to connect each row of your keypad, and also be certain
to pull all four column inputs (C0..C3) to ground with four 4.7K Ohm resistors as illustrated in
Figure Two.
BEEPER CONNECTION
In order to provide tactile feedback to the operator, the Beeper Output (Pin 18) of the EDE1144 is
designed to drive a piezo beeper or speaker via a NPN transistor such as the 2N2222. Figure
Two illustrates a typical common-emitter configuration. With the common-emitter drive
configuration, be certain to use a resistor from the EDE1144 Beeper Output (Pin 18) to the
transistor's base pin to limit base drive current. Your particular beeper may or may not require a
resistor in series with it to limit current. The drive signal is a 1KHz square wave, toggling from 0
to 5 Volts, with a duration of 45mS.
RS-232 OUTPUT
The RS-232 Output (Pin 1) transmits serial data to the host microcontroller. This data is sent at
either 2400 or 9600 Baud, as selected by Pin 2. Data is send in traditional N-8-1 (no parity, 8
data bits, one stop bit) format at TTL/CMOS voltage levels; i.e. 0V to 5V. This serial output
signal can be connected directly to the host microcontroller's serial input pin without any type of
voltage level conversion. However, if data is to be sent to a device expecting RS-232 voltage
levels of -12V to +12V (such as a PC), a voltage level conversion IC such as the MAX232 will be
needed between the EDE1144's serial output pin and the PC's serial input pin.
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