Motor TRANSISTOR ONE TRANSISTOR THREE POWER + POWER + POWER - POWER - current flow current flow current flow Motor TRANSISTOR TWO TRANSISTOR THREE TRANSISTOR FOUR POWER + POWER + POWER - POWER - TRANSISTOR ONE ENABLE DIRECTION AND gate AND gate Inverter AND gate Inverter AND gate DIRECTION Enable Motor 1 Direction A Direction B Motor Power M1 Enable Motor 2 Direction A Direction B M2 Motor Ground Block Diagram of the L293 Motor Driver Chip Pin 1 Pin 2 Pin 7 Pin 3 Pin 6 Pin 8 Pin 9 Pin 10 Pin 15 Pin 11 Pin 14 Pins 4,5, 12,13 Pin 16 Logic Reference Voltage H-Bridge Motor Driver Circuit H-Bridge Motor Driver Circuit [...]... of light being transmitted by the IR LEDs For 6.270 purposes, the ampli er is kept at full brightness, but there may be applications where this feature is useful +5V U10 2 1 4 6811 E clock 6811 Port A6 U12/74HC04 5 6 Timer Output 2 CLR CLKA CLKB 14 CLR 15 CLKA 12 CLKB 3 QA 5 QB 6 Q C 7 Q D 13 QA 11 QB 10 Q C 9 Q D U12/74HC04 9 8 R14/1K U11 pin 6= motor power pin 4= motor ground U11/LM386 3 R15/1K 5... memory is part of the 6811 circuit When the 6811 is operated in single-chip mode, the upper-eight-bit address bus and multiplexed address/data bus become general purpose inputs and outputs of the 6811, controllable by system software Thus, in single-chip mode, the 6811 could communicate with the LCD with a software driver, rather than the too-fast hardware communication There is a problem with this,... state This solution is implemented with resistor-capacitor delay circuits connected to a mode input pin of the 6811 and the logic gate that enables the RAM These circuits are shown in Figure B.9 The C11, R9, and R10 circuit is connected to the mode input pin MODA of the 6811 During a power-on condition, the 6811 will come out of its reset state before capacitor C11 is fully charged thus, it will register... that is blinking on and o at a particular rate The GP1U52 sensor is tuned to 40,000 Hertz (40 KHz) In TV remote applications, a data stream is then generated around the 40 KHz carrier frequency The signal consists of bursts and gaps of the 40 KHz transmissions For the 6.270 application, the 40 KHz carrier is used to tranmit a square wave of relatively low frequency (100 or 125 Hz), as shown in Figure... one microamp to a circuit (Alkaline batteries have a shelf life of several years.) Having a battery-backed static memory greatly increases the usability of the 6.270 board A robot can simply be turned on and operated immediately, without having to be connected to a computer rst Unfortunately, implementing a battery-backed RAM can be complicated The di culty arises from unpredictabilities in microprocessor... IR LEDs, is software-controllable B.7.1 The IR Beacon Figure B.24 shows the schematic for the IR beacon Each infrared LED has a visible LED in series with it so it should be easy to ascertain that the device is transmitting APPENDIX B 6.270 HARDWARE 212 RP8/47Ωx4 RP9/47Ωx4 + - LED23-30 Red LED's LED31-38 MLED71 IR LED's Figure B.24: Infrared Beacon Circuit infrared light properly The resistors act... through any branch of the circuit to between 10 to 20 mA B.8 The LCD Display The rst fourteen pins of the 6.270 Board's Expansion Bus are designed to be compatible with a 14-pin standard LCD bus A variety of character-based LCD devices with di erent screen sizes use this standard bus The LCD bus standard is fairly simple, consisting of the following signals: an 8-bit data bidirectional bus two mode... interrupt exits without taking action If power does not return after about one-hundredth of a second, the software routine executes a machine-language HALT instruction, which shuts o the microprocessor This sequence of actions implements an orderly shutdown sequence B.6.3 The Power-Up Delays To make sure that the 6811 does not corrupt memory while it is being powered on, the 6811 is made to enter a particular... Figure B.21: Sharp IR Sensor Decoding IR-Encoded Square Wave Divide-by-50 Counter ’390 6811 E clock 2 MHz Modulated 40 KHz Power Amp Enable IR light emitter Modulation Ctrl Brightness Control (100 or 125 Hz) Figure B.22: Block Diagram of Infrared Circuitry B.7 THE INFRARED TRANSMISSION CIRCUIT 211 divide-by- fty function by ganging two of the divide-by- ve counters and one of the ip- ops The IR control... memory and for the microprocessor circuit) retain charge for a brief period after power is 208 APPENDIX B 6.270 HARDWARE switched o The diodes prevent this charge from \ owing backward," and allowing one part of the circuit to power another When power is switched o , the power-o interrupt signal immediately goes low However, system capacitors (mostly, C13) will keep the microprocessor powered up for a . 10 3 8 3 3 9 5 22 2 21 4 20 12 4 13 2 14 5 15 1 16 12 17 15 18 14 19 13 23 1 24 12 25 15 26 14 27 13 11 5 2 413141 5121 676767 Host ComputerRobot Board signal ground Robot receive data Robot transmit data RJ-11. E1 6811 Port E3 6811 Port E2 2 4 210 10 2 12 10 3 1 6 3 11 1 14 3 14 3 11 1 6 3 3 1 4 3 2 16 8 816 12 13 15 9 7 11 15 15 1 6 7 3 16 9 1 5 19 9 2 1 5413 12 13 12 5 4 13 8 14 7 17 4 18 3 1 2 2 2 2 11 11 11 5 Power Switch 6v. 10µF +5V U7/74HC132 R2/47K C3 4700pF U7/74HC132 R3 100K R4 10K R6/2,2K LED11 RP3/1K +5V LED12 RP3/1K 6811 Port D1 6811 Port D0 12 5 1 3 7 14 15 11 10 11 12 13 4 RS232 TxD RS232 RxD 1 2 13 2 6 9 3