NXP capacitive sensor
demo board OM11057
Fast, easy evaluation of capacitive
sensors
This`board,`equipped`with`an`LCD`driver`and`controlled`by`a`Cortex-M0™`MCU,`demonstrates`the`
features`of`two`capacitive`sensor`devices.
Key features
`
` 8-channel`capacitive`sensor`PCF8885
`
` 2-channel`capacitive`sensor`PCA8886
`
` LCD/LED`driver`PCF8536
`
` Cortex-M0`LPC1111`with`8`KB`flash`memory
`
` Standalone`operation
`
` Powered`via`two`AA`batteries`or`USB
`
` Software`modifications`via`LPC-Link
`
` Sounder`for`audible`feedback
Applications
`
` Hermetically`sealed`keyboards
`
` Proximity`detection
`
` Switches`in`medical`and`explosive`environments
`
` Vandal-proof`switches
`
` Gaming`devices
`
` Portable`communications
`
` Fixed`and`mobile`entertainment`systems
`
` White`goods
`
` Automotive`(e.g.`passive`keyless`entry)
The`NXP`OM11057`demonstrates`the`features`of`the`PCF8885,`
an`8-channel`capacitive`sensor,`the`PCF8886,`a`2-channel`
capacitive`proximity`sensor`and`the`PCF8536,`an`LCD/LED`
controller`which`can`be`used`to`drive`an`LCD`and`the`
accompanying`backlight.`The`board`is`controlled`by`a`
low-cost,`32-bit`Cortex-M0`microcontroller`LPC1111.``
An`LPC-Link`debug`probe`is`also`included`with`the`board,`
so`designers`can`easily`modify`the`firmware`or`reprogram`
the`LPC1111`using`NXP’s`low-cost`LPCXpresso`development`
platform.
The`sensor`PCF8885`is`configured`to`control`a`total`of``
20`sensors:`the`slider`(eight`channels),`the`wheel`(eight`
channels),`and`four`buttons.`The`device’s`very`high`sensitivity`
delivers`reliable`operation,`even`though`it’s`covered`by`
plexiglass`(acrylic`glass).`The`proximity`sensor`PCA8886`
uses`one`of`its`two`channels`to`detect`whether`a`hand`is`
approaching`the`controls.`The`other`channel`can`be`connected`
to`an`external`sensor.`The`LCD/LED`driver`PCF8536`controls`
both`of`the`board’s`LCDs`using`a`multiplex`rate`of`eight.`
Capacitive sensor PCF8885
This`8-channel`proximity`switch`uses`a`patented`(EDISEN)`
method`to`detect`a`change`in`capacitance`on`remote`sensing`
plates.`Changes`in`the`static`capacitance`(as`opposed`to`
changes`in`the`dynamic`capacitance)`are`automatically`
compensated`using`continuous`auto-calibration.`The`eight`
input`channels`operate`independently`of`each`other.`The`
device`offers`built-in`support`for`a`matrix`sensor`arrangement.`
In`this`set-up,`the`device`generates`an`interrupt`when`two`
channels`are`activated`simultaneously,`and`suppresses`
additional`channel`outputs`when`two`channels`are`already`
active.`
Capacitive proximity sensor PCA8886
This`device`uses`the`same`operating`principle`as`the`PCF8885.`
Remote`sensing`plates`(e.g.`conductive`foil)`can`be`connected`
directly`to`the`IC`or`remotely`using`coaxial`cable.`The`device`
can`be`used`on`its`own,`without`a`microcontroller.`
The OM11057 includes an LPC-Link JTAG/SWD debug probe
LCD/LED driver PCF8536
This`device`generates`the`drive`signals`for`any`multiplexed`
LCD`with`up`to`eight`backplanes,`up`to`44`segments,`and`up`
to`320`elements.`It`is`compatible`with`most`microcontrollers`
and`microprocessors,`and`communicates`via`a`two-line,`
bidirectional`I
2
C-bus`or`a`three-line,`unidirectional`SPI-bus.`
A`display`RAM`with`auto-incremented`addressing`minimizes`
communication`overhead.`An`on-chip`PWM`controller`
supports`LED`illumination.`Up`to`six`independent`PWM`
channels`can`be`configured,`each`with`128`levels.`This`makes`
it`possible`to`configure`two`RGB`controllers`with`more`than`
two`million`colors`each.`The`PWM`channels`can`also`be`used`
for`static`drive.`The`Q900`types`of`this`device`are`AEC-Q100`
compliant`and`offer`a`target`operating`temperature`of`95`°C.
Device
Features
`
` ` ynamic`proximity`switch`with`eight`input`channels,`digital`
D
processing`
`
` ` upport`for`matrix`arrangement`of`sensors`for`up`to`24`keys`
S
using`one`PCF8885`(4`x`4`matrix,`plus`8)
`
` Continuous`auto-calibration`
`
` I
2
C`Fast-mode`compatible`interface
`
` Clock`and`interrupt`cascading`of`two`ICs`for`up`to`80`keys`
`
` Low-power`battery`operation`(IDD`~`10`µA)
`
` Sleep`mode`(IDD`<100`nA)
`
` Adjustable`response`time
`
` Adjustable`sensitivity
`
` TSSOP28`package`(others`available`on`request)
`
` ` ynamic`proximity`switch`with`two`input`channels,``
D
digital`processing`
`
` Continuous`auto-calibration,`
`
` Adjustable`sensitivity,`can`be`made`very`high
`
` Adjustable`response`time
`
` Wide`input`capacitance`range`(10`to`60`pF)
`
` Sensing`plate`and`IC`can`be`several`meters`apart
`
` Low-power`battery`operation`(I
DD
`=`6`µA`typical)
`
` Output`configurable`as`push-button,`toggle,`or`pulse`
`
` TSSOP16`package`(others`available`on`request)
`
` AEC-Q100`compliant`for`automotive`applications
PCF8885
PCF8886
www.nxp.com
© 2011 NXP Semiconductors N.V.
All rights reserved. Reproduction in whole or in part is prohibited without the prior written consent of the copyright owner. The
information presented in this document does not form part of any quotation or contract, is believed to be accurate and reliable and
may be changed without notice. No liability will be accepted by the publisher for any consequence of its use. Publication thereof
does not convey nor imply any license under patent- or other industrial or intellectual property rights.
Date of release: February 2011
Document order number: 9397 750 17066
Printed in the Netherlands
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