Design of a Wireless Laser Pointer Based on MCU

Transcription

1 Applied Mechanics and Materials Online: ISSN: , Vols , pp doi: / Trans Tech Publications, Switzerland Design of a Wireless Laser Pointer Based on MCU Sheng Dong 1, a, Zhexu Wang 2,b, Xirui Gao 3,c, Jing Yao 4,d 1 Beihua University,JiLin,China a dswlpdsx@163.com, b uioj2012@163.com, c g @163.com, d @163.com Keywords: STC89C52RC PS/2 mouse USB2.0 protocol Wireless laser pointer. Abstract. Wireless laser pointer is widely used in multimedia teaching. Due to the usage of professional high speed USB interface chips and USB2.0 protocol, the price of a wireless laser pointer in the market with the only function of changing PPT pages is about 50 dollar.this paper completes a very low price design of wireless laser pointer for multimedia teaching use based on STC89C52RC MCU and nrf905 single-chip radio transceivers,which can complete not only PPT page turning forward or backward but also black screen, drawing lines with fluorescent pen or needlepoint. Introduction Wireless laser pointer is widely used in multimedia teaching. The majority method of the wireless communication is based on USB2.0 protocol[1]. Due to the development of USB devices needing professional USB interface chips, such as USB device chip Cypress CY7C68013[2],Philips PDIUSBD12[3],master-slave transformation type (OTG) USB chip ISP1362[4], therefore, the price of a wireless laser pointer in the market with the only function of changing PPT pages is about 50 dollar, but the PS/2 mouse protocol is very simple, without special hardware interface chips,only a STC89C52RC MCU[5] and RF communication chips can complete all of the control works, so the whole price reduced by half, therefore, in this paper, presentes a design of wireless laser pointer based on STC89C52RC MCU and nrf905 RF chips. Hardware design of wireless laser pointer The system block diagram.fig.1 shows the system block diagram of the wireless laser pointer.the main controller receives the signal coming from the handset,and sends them to PC through the PS/2 mouse port to control the PPT player to go ahead or backward,draw a corlorful line or do some special emphases on the screen,just like a real mouse is working. NRF905 is a single-chip radio transceiver for the 433/868/915 MHz ISM band, its configuration is easily programmable by use of the SPI interface. Current consumption is only 9mA in transmit at an output power of -10dBm, and in receive mode 12.5mA[6]. Handset nrf905 nrf905 The main controller Fig.1. System block diagram of the wireless laser pointer PS/2 mouse port PC Circuit diagram of system.fig.2 shows the circuit diagram of the main controller. Fig.3 shows circuit diagram of the handset. All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (ID: , Pennsylvania State University, University Park, USA-21/02/16,07:21:50)

2 Applied Mechanics and Materials Vols R2 10K 10uF VCC C3 TXEN CD CSN MOSI SCK RST P3.0 P3.1 P3.2 CLK P3.3 DR P3.4 SDA P3.5 TRX_CE P3.6 P3.7 X2 X1 AT89C52RC 1 P1.0 2 P1.1 3 P1.2 4 P1.3 5 P1.4 6 P1.5 7 P1.6 8 P1.7 9 RST 10 RXD 11 TXD 12 INT0 13 INT1 14 T0 15 T1 16 WR 17 RD 18 XTAL2 VCC 40 P P P P P P P P EA 31 ALE 30 PSEN 29 P P P P P P XTAL1 P P VCC VCC P0.0 P0.1 P0.2 P0.3 P0.4 P0.5 P0.6 P0.7 VCC ALE P2.7 P2.6 P2.5 P2.4 P2.3 P2.2 P2.1 P2.0 TXEN TRX_CE CD MOSI SCK CSN DR NRF905 X1 X2 22p 22p C1 C MHz VCC STC89C52RC VCC NRF905 TXEN 1 P1.0 VCC 40 P0.0 VCC 1 2 P1.1 P TXEN RESET P P1.2 P CSN P0.2 3 C3 4 P1.3 P TRX_CE 10uF TRX_CE P P1.4 P MOSI P P1.5 P CD RST P P1.6 P SCK P P1.7 P MOSI C9 RST P RST P SCK R2 P RXD EA 31 CSN 104 P TXD ALE 30 DR 10K C10 P INT0 PSEN 29 P3.3 DR P INT1 P P3.4 P T0 P P3.5 P T1 P MHz P3.6 P WR P X1 X2 P3.7 P RD P C1 22p 22p X2 P2.2 C2 VCC 18 XTAL2 P X1 P XTAL1 P P P S1 P3.4 S2 P3.5 S3 P3.6 S4 P3.7 Fig.2. Circuit diagram of the main controller Fig.3. Circuit diagram of the handset S5 S9 S6 S10 S7 S11 S8 S12 P3.0 P3.1 P3.2 System software programming PS/2 serial communication port. pin1:data,pin4:+5v,pin3:, pin5:clock. PS/2 protocol of the serial port communication. PS/2 clock signal is produced by the mouse, even the host sends data to device, it also must tell mouse when to begin to produce the clock signal first..its maximum clock frequency is 33 KHz. Data sent from the mouse to the host is read on the falling edge of the clock signal, data sent from the host to the mouse is read on the rising edge, when the host sends data to the mouse, each byte in the Data line contains 12 bits, these bits are shown in Fig.4, the meaning of the ACK is an active low acknowledge bit sent by mouse, PARITY is an odd check bit.fig.4. shows the format of the data sending from host to mouse[7]. Fig.4.The format of the data sending from host to mouse Fig.5 shows the format of the data sended from mouse to the host. Fig.5. The format of the data sended from mouse to host Software program flow chart of the host controller. Fig.6 shows the main controller s program flow chart. When MCU simulates the action of press mouse left button,it sends data to host PC in the sequence of instructions:0x09,0x00,0x00,0x00;when press right button,it sends the sequence of instructions:0x0a,0x00,0x00,0x00;when mouse wheel scrolls up a grid (corresponding to turn back a page of PPT),it sends instructions sequence:0x08,0x00,0x00,0xff;when mouse wheel scrolls down a grid (corresponding to turn forward a page of PPT),sends instructions sequence: 0x08,0x00,0x00,0x01; When mouse moving left 10 unit grids sends sequence of instructions: 0x18,0xf8,0x00,0x00; When mouse moving right 10 unit of grids sends sequence of instructions: 0x08,0x08, 0x00, 0x00; When mouse moves down 10 unit of grids,it sends sequence of instructions: 0x28,0x00,0xf8,0x00; When mouse moves up 10 unit of grids,it sends sequence of instructions: 0x08,0x00,0x08,0x00.

3 3260 Vehicle, Mechatronics and Information Technologies Start nrf905 initialization: Initialize nrf905 to standby mode ; Configurate nrf905 to receive mode; Set the operating frequency, output power, no retransmission mode, receiving Valid data length is 4 bytes, receive address, and 8-bit CRC check; Clear mouse initialization successful flag,mouse_init_success =0. The beginning of the mouse initialization: Set clock line, interrupt trigger mode 0, the highest priority; Sent to the host 0xAA;Delay of 200 ms;sent to the host 0x00; Clear interrupt flag bit;enable external interrupt;enable interrupt bit. N Mouse initialization succeeds? Y Wait for the PS/2 clock interrupt signal arrival and receive instructions from the PC. Call instruction analysis program Has nrf905 received data? Y? According to the received commands, perform various functions of the mouse (press left or right button, move left or right, move up or down and roller actions) N Fig.6. Main controller program flow chart Software program flow chart of the handset. Fig.7 shows the handset software program flow chart. start Initialize nrf905 to standby mode;configurates nrf905 into launch mode; Set the operating frequency, output power, retransmission mode,sending valid data length is 4 bytes,set transisition address and the 8-bit CRC. Scan the keyboard and send corresponding commands to the main controller: For example,press the mouse left button,send 0x01, press the mouse right button,send 0x02, the mouse wheel up,send 0x03, the mouse wheel down,send 0x04. Fig.7. Handset software program flow chart System debugging and analysis of experimental results When presses the PPT page forward button on the handset, the main controller receives the message and sends it to the host in command sequences: 0x08,0x00,0x00, 0x01. Using the digital storage oscilloscope to measure its waveform shown infig.8.. In the Fig.8. the signal above is the Clock; Signal underneath the Clock is the Data.

4 Applied Mechanics and Materials Vols Fig.8. Command sequence diagram sended to the host for PPT page forward Using logic analyzer to measure the mouse initialization command sequence: Mouse sending/host replying:0xaa, 0x00/0xf2; 0xfa,0x00/0xe8; 0xfa,0x00/;0xfa,/0xe6; 0xfa,/0xe6;0xfa,/0xe9;0xfa,0x00,0x00,0x64/0xe8;0xfa,/0x03;0xfa,/0xf3;0xfa,/0xc8;0xfa,/0xf3;0xfa, /0x64; 0xfa,/0xf3;0xfa,/0x50;0xfa,/0xf2;0xfa,0x03/0xf3; 0xfa,/0xc8; 0xfa,/0xf3;0xfa,/0xc8;0xfa,/0xf3; 0xfa,/0x50;0xfa,/0xf2; 0xfa,0x03/0xf3; 0xfa,/0x64; 0xfa,/0xe8; 0xfa,/0x03; 0xfa,/0xf4;0xfa. Conclusions Not only completes PPT page turning forward and backward functions but also achieves a variety of control functions that can be verified through the wireless laser poniter, such as: black screen, fluorescent pen, needlepoint drawing lines, and other functions.using STC89C52RC and nrf905 to achieve the control functions of multimedia teaching laser pointer on a very low price. References [1] Universal Serial Bus Specification, Information on [2] CYPRESS, product specification, CY7C68013_datasheet.pdf, Information on [3]PHILIPS,product specification,pdiusbd12_datasheet.pdf, Information on [4]PHILIPS, ISP1362 DatsSheet.pdf, Information on [5]STC, STC89C51_GUIDE.pdf, Information on [6] NORDIC, product specification, nrf905_datasheet.pdf, Information on [7]Adam Chapweske, Technical reference of the PS/2, Information on

5 Vehicle, Mechatronics and Information Technologies / Design of a Wireless Laser Pointer Based on MCU /