8/14/2019 An 2362

1/7

Application Note AN2362

Wireless Remote Control with Capacitive Sensing

Author: Oleksandr KarpinAssociated Project: Yes

Associated Part Family: CY8C21x34, PRoC

CYWUSB6953Software Version: PSoC Designer4.2 SP3

Associated Application Notes: None

AbstractThis Application Note describes the integration of the Cypress WirelessUSB and PSoC CapSenseinterface technologies into a wireless remote control with capacitive sensors. This implementationdemonstrates a WirelessUSB two-way simple protocol, a mixed-signal PSoC device, and implementation ofthe capacitive switch design using the CSR user module in PSoC Designer. The proposed device can beused as a design starting point for the many popular wireless devices that markets demand today.

IntroductionA wireless remote control has the followingadvantages over traditional infrared signal (IR)-based remote controls:

o It does not require face-to-face devicedirectivity.

o It allows for control through a wall.o It can operate with many devices

simultaneously.o It allows for the use of several wireless

devices in a shared room space.

Capacitive sensors have advantages overtraditional mechanical switches, including greaterreliability and lower cost. Integration of theCypress WirelessUSB and PSoC CapSensetechnologies into a wireless remote control withcapacitive sensors combines all theseadvantages in a single device. The unique

architecture of the PSoC allows this device to bebuilt at a very affordable price with externalcomponents kept to a minimum. The wirelessremote control with capacitive sensors can beused as a remote control for various devices (TVsets, air-conditioners and similar homeappliances), in distance-measuring equipment,medical systems and related devices.

Figure 1. Block Diagram of Wireless RemoteControl with Capacitive Sensors

Keypad

Capacitive

Control

WirelessUSB

TX devicePSoC

WirelessUSB

RX devicePSoCAction

A block diagram for this wireless remote control isshown in Figure 1. Technical specifications arelisted in Table 1.

7/21/2006 Revision A - 1 -

8/14/2019 An 2362

2/7

AN2362

Table 1. Specifications for Wireless Remote Controlwith Capacitive Sensing

Item Specification

Power Supply Voltage

(2 AA, AAA Batteries)

0.93.2V

Remote Device Power

Consumption (Average Values)

-Reconnect Mode

-Data Transfer (Connected) Mode1

3 mA

150-200 A

Receiver Device Power

Consumption (Continuous

operation)

60 mA

Wireless Protocol Two-Way

WirelessUSB

Data Rate 64 kbps

Operation Range 10 meters or

more

The proposed wireless remote control device withcapacitive sensors is described in the followingsections:

DeviceSchematicWirelessUSB Two-Way ProtocolAppendix

Device SchematicA complete schematic of the remote controldevice is shown in Figure 4 (Appendix).

Using PSoC Designers CSR User Module, thePSoC device U1 detects the presence of a fingerthrough glass, plastic, acrylic or many other non-metallic materials on a simple PCB trace througha CapSense button. The PSoC SPIM UserModule permits communication by means of theWirelessUSB radio transceiver, CYWUSB6934.The firmware modules for working with this radiotransceiver were taken from the WirelessUSB LSdevelopment kit, CY4632 WirelessUSB LS

Keyboard-Mouse Reference Design Kit withKISSBind

. The PSoC device also implements a

two-way communication protocol and other task-oriented control functions. For more informationabout the PSoC application, see the associatedproject files.

The WirelessUSB radio transceiver,CYWUSB6934, must be connected to theconnector J1. The connector J2 provides the in-circuit PSoC programming firmware.

1The proposed implementation in this Application Note is not

optimized for minimal power consumption. It is possible tosignificantly decrease current consumption by increasing thetime interval between transferred packets.

The remote device user interface (panel) isaccessed through an array of CapSense buttons(BRight, BDown, BOK, BUp, BLeft), LEDs (D1-D5) and buzzer (Y1). When the user touches thebuttons on the remote device, the correspondingLEDs light up on both the remote and receiver

devices (if the devices are connected). Thisprovides for remote control of wireless LEDs bycapacitive sensors. The buzzer Y1 allows one tosearch the remote device by toggling the BFindswitch on the receiver. In this mode, the buzzeron the remote device beeps and all the LEDslight up. The proposed implementation is aprototype, but can be used as a design startingpoint for wireless devices required by todaysmarket. It is also possible to add capacitivesliders, rotating wheels, and other options for amore feature-rich user interface.

To provide a processor power supply from a lowvoltage level, the boost converter U2 is used. Forexample, the low-cost XCY672S Torex series ofDC/DC converters with output voltage equal to3.06V can be used. The Torex DC/DC convertersare optimized to extend the battery life forwireless peripherals that are designed with theCypress WirelessUSB radio SoC andmicrocontrollers (seehttp://www.torex.co.jp/english/).

This implementation can easily be adapted forthe CYWUSB6953 WirelessUSB PRoC(Programmable Radio System-on-Chip). Formore information about the WirelessUSB FlashProgrammable MCU + Radio see Wireless

Products on the Cypress web site.

The schematic of the receiver is shown in Figure5 (Appendix). The schematic is similar to theschematic for the remote control device inFigure 4, described earlier in this ApplicationNote.

7/21/2006 Revision A - 2 -

http://www.torex.co.jp/english/http://www.torex.co.jp/english/

8/14/2019 An 2362

3/7

AN2362

WirelessUSB Two-Way ProtocolA WirelessUSB two-way communication protocolis shown in Figure 2. For more information aboutWirelessUSB communication protocols, seeCY4632 WirelessUSB LS Keyboard-MouseReference Design Kit with KISSBind on theCypress web site. Note that existing two-wayWirelessUSB communication protocols aredesigned only for stationary receivers. Thereceiver in this application is stationary and itspower consumption is not minimized. Only theremote control is designed to be a portabledevice with low power consumption.

By adding time synchronization between theremote control and the receiverwhich allowsthem to remain in sleep mode most of the timeboth devices are portable. A user can easily addthis time-synchronization feature.

Wireless communication between devicesrequires the use of the same frequency,PN code, and code seed. Therefore, at the startof communication, an automatic channel-selection procedure is performed. The remotedevice selects the first available channel, sets the

default code seed and PN code, repeatstransmission of the connect-request datapackets, and listens for the connect-responsepackets. If the response time-out has expired anda response is not received, then the remotedevice goes to the Start state, selects the nextavailable channel, and again attempts aconnection. The remote device also sets thedefault code seed and PN code. With thesevalues, the remote control successively listens toall channels for the connect-request packet.When the remote device receives the connect-request packet, it immediately sends a response.

Figure 2. WirelessUSB 2-Way Communication Protocol

ChannelAvailable?

Go To NextChannel

Set TX_SEEDRandom

no

Connect Request

Remote Device Receiver Device

Listen Time-out

Set TX_SEED

Connect Response

Set TX_SEED

Connect Response Time-out

Ping Request

Connect Request

Ping Response

Ping Response Time-out

Data

Data Response

Data Response Time-out

Listen Time-out

Ping Request Time-out

Data Receive Time-out

Listen for Connect

Request

Go To Next

Channel

yes

Start Start

Set Default Channel

PN Code, SEED

Set Default

PN Code, SEED

After the remote device sends the connect-response packet and the receiving devicereceives this packet, the two devices set the newselected code seed value TX_SEED and try toping the channel for verification. This randomunique code seed value protects the data frombeing interpreted by similar devices as their own.

After a correct pinging response, the devices gointo the Data Transmissionstate. In every state,both devices control the operation of the Time-out Expired event. When the Time-out Expiredevent appears, the devices go to the Startstateand begin all over again. This is the main rule ofthe communication protocols.

7/21/2006 Revision A - 3 -

8/14/2019 An 2362

4/7

AN2362

To simplify the protocol, the PN code in thisapplication is constant.

Remote device power consumption is minimizedby using sleep mode between data transfers.Increasing sleep time (or time between packet

transfers) decreases power consumption.However, in sleep mode the capacitive sensorinterface is not active. This decreases theresponsiveness of the device. An adaptive sleepmode addresses this problem. Every 125 milli-seconds (ms) the microcontroller wakes up andchecks the button state. The device only wakesthe radio module and sends a data packet if thebutton state has changed. Otherwise, the high-power-consuming radio module stays in sleepmode and the PSoC also returns to sleep mode.

To verify connection between devices andprovide for data transfer from the receiver to theremote device, a data packet is sent at leastevery second. This is how the Find RemoteDevicesignal is sent from the receiver.

ConclusionThis Application Note describes the CypressWirelessUSB and PSoC CapSense interfacetechnologies. A wireless remote control withcapacitive sensors is proposed. A PSoC projectand implementation of the capacitive switchdesign using the CSR User Module in PSoCDesigner have been developed. A simple two-way WirelessUSB protocol has been designed.The proposed implementation can be used as adesign starting point for a wide variety of popularwireless applications.

Figure 3. Wireless Remote Control Device with Capacitive Sensors (Actual Size)

7/21/2006 Revision A - 4 -

8/14/2019 An 2362

5/7

AN2362

Appendix: SchematicsFigure 4. Schematic of the Remote Device

P0[7]1

P0[5]2

P0[3]3

P0[1]4

P2[7]5

P2[5]6

P2[3]7

P2[1]8

Vss9

P1[7]10

P1[5]11

P1[3]12

P1[1]13

Vss14

P1[0]15P1[2]16P1[4]17P1[6]18

Xres19

P2[0]20P2[2]21P2[4]22P2[6]23

P0[0]24P0[2]25P0[4]26P0[6]27

Vdd28

U1

CY8C21534

VDD

123456789

1011121314

J1

WirelessUSB Module

12345

J2

ISR

nPD_WIRQ_W

nRESET_W

nSS_WMOSI_W

XRES

SCK_W

MISO_WSDA

Y1

LX3

VSS

1

VOUT 4

U3

XCY672S011PR

Buzzer

D6 MA2Q735L1 100uH

VDD

IRQ_W

nPD_W

MOSI_WnSS_W

nRESET_W

SCK_WMISO_W

CYWUSB6934

VDD

VDD

XRES

SDASCL

D1R1

820

nL_R

+

C3

47u

D2R2

820nL_D

R3

820

D3

D4R4

820nL_U

D5R5

820

SCL

nL_OK

nL_L

BAT+

BAT-

+

C1

220u

BRight

BDown

BOK

BUp

BLeft

VDD

C2 0.1u

7/21/2006 Revision A - 5 -

8/14/2019 An 2362

6/7

AN2362

Figure 5. Schematic of the Receiver Device (Powered from Battery)

P0[7]1

P0[5]2

P0[3]3

P0[1]4

P2[7]5

P2[5]6

P2[3]7

P2[1]8

Vss9

P1[7]10

P1[5]11

P1[3]12

P1[1]13

Vss14

P1[0]15P1[2]16P1[4]17P1[6]18

Xres19

P2[0]20P2[2]21P2[4]22P2[6]23

P0[0]24P0[2]25P0[4]26P0[6]27

Vdd

28

U1

CY8C21534

VDD

123456789

1011121314

J1

WirelessUSB Module

12345

J2

ISR

IRQ_WnPD_W

nSS_W

nRESET_W

MOSI_W

XRES

MISO_W

SCK_W

SDA

LX3

VSS

1

VOUT4

U3

XCY672S011PR

D6 MA2Q735L1 100uH

VDD

nPD_W

nSS_WnRESET_W

IRQ_W

SCK_W

MOSI_W

VDD

MISO_W

VDD

SCLSDA

XRES

R1

820

D1nL_R

+ C3

47u

D2nL_D

R2

820R3

820

D3

D4nL_U

R4

820D5R5

820

SCL

nL_OK

nL_L

BAT+

BAT-

+C1

220u

BFind

VDD

C2 0.1u

CYWUSB6934

7/21/2006 Revision A - 6 -

8/14/2019 An 2362

7/7

AN2362

About the Author

Name: Oleksandr KarpinTitle: Post-Graduate Student

Background: Oleksandr received a computer-

engineering degree in 2001from National University"Lvivska Polytechnika"(Ukraine), and continues hisstudy there as a post-graduatestudent. His interests includeembedded systems design andnew technologies.

Contact: karpinoo@ukr.net

Cypress Semiconductor2700 162nd Street SW, Building D

Lynnwood, WA 98087Phone: 800.669.0557

Fax: 425.787.4641

http://www.cypress.com/Copyright 2006 Cypress Semiconductor Corporation. All rights reserved.

PSoC is a registered trademark of Cypress Semiconductor Corp."Programmable System-on-Chip," PSoC Designer and PSoC Express are trademarks of Cypress Semiconductor Corp.

All other trademarks or registered trademarks referenced herein are the property of their respective owners.The information contained herein is subject to change without notice. Made in the U.S.A.

7/21/2006 Revision A - 7 -

mailto:karpinoo@ukr.nethttp://www.cypress.com/http://www.cypress.com/mailto:karpinoo@ukr.net