MCS3142 datasheet(25/57 Pages) MICROCHIP

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MCS3142 Dual KEELOQ® Encoder Wireless Remote Control Development Kit User’s Guide

DS40001746A-page 24

 2014 Microchip Technology Inc.

5.8

PUSH BUTTONS

The Embedded Security Development Board has two sets of push buttons. SW1-SW4

on the target application side and SW5 on the host controller side.

The four push buttons for the target application microcontroller are read as a single

analog input. Depending on the different ratios of pull-up and pull-down resister values,

the input analog voltages to the master microcontroller are different. Therefore, through

the ADC on the target application microcontroller, the button that is pressed can be

identified. Such design is used to save I/O pin requirement for the target application

microcontroller.

The four push buttons for the host microcontroller are four separate digital inputs to the

slave microcontroller, due to the abundant I/O pin availability for the slave

microcontroller. All buttons are assigned to the individual interrupt lines of the

microcontroller and are not driven by external pull-up circuitry to save power

consumption. The user software must enable the PORTB pull-ups of the

microcontroller before evaluating the button state.

The MCLR push button is connected to the RE3/MCLR pin of the target application

microcontroller. The RE3/MCLR pin of the target application microcontroller is also one

of the SPI lines that control the host microcontroller. When the target application and

host microcontrollers are interconnected, the RE3/MCLR pin of target application

microcontroller is configured to be a normal digital I/O pin; therefore, the MCLR push

button is ineffective. Otherwise, if an I2C intercommunication is not required between

the target application and host microcontroller, the pin can be configured as Reset and

the MCLR button can be used.

5.9

LEDS

There are two sets of LEDs that are controlled by the target application and the host

microcontrollers, respectively. The target application MCU controls a set of four LEDs

through the digital output pins. The host MCU controls a set of six LEDs through digital

output pins. The two sets of LEDs may be useful in the demo or debugging process.

LEDs D15 and D16 on the left half are used to identify the TX and RX operation of

MCP2200. The default configuration of the MCP2200 does not enable this feature, but

it may be enabled using the MCP2200 configuration utility (see Section 7.2 “Install”).

LEDs D12 and D13 are used by the preprogrammed demo firmware to identify the TX

and RX communication between the host and target microcontrollers.

LED D2 indicates the power availability. This LED cannot be controlled by the target

application or by the host microcontroller.

5.10 POWER SUPPLY

The Embedded Security Development Board can be powered by one of the following

two sources:

•USB port

• External 3.3V power source through GND and +VEXT connectors

Jumper J6 is used to choose the power source. When the left side, pins 1-2 of J6 are

closed, USB power is selected; when the right side, pins 2-3 of J6 are closed, external

power source is selected.

When the USB port is used to power the board, the input voltage is stabilized by a

Microchip MCP1703, LDO regulator U3.

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