book

Experimenting with Raspberry Pi

by Warren W. Gay

November 2014

Beginner

248 pages

4h 40m

English

Apress

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CharacteristicsCircuitProtocolOverall ProtocolData BitsData FormatSoftwareChosen ApproachExample RunSource Code
DC CharacteristicsGPIO Output CurrentGPIO InputsStandby CurrentInput Logic LevelsOutput Logic LevelsReset TimingCircuitI2C BusWiring and TestingSoftware ConfigurationGeneral ConfigurationMain ProgramModule i2c_funcs.cModule sysgpio.cExample RunResponse Times
Project OverviewNunchuk FeaturesConnector PinoutTesting the ConnectionNunchuk I2C ProtocolEncryptionRead Sensor DataLinux uinput InterfaceWorking with Header FilesOpening the Device NodeConfiguring EventsCreating the NodePosting EV_KEY EventsPosting EV_REL EventsPosting EV_SYN EventsClosing uinputX-WindowInput UtilitiesTesting the NunchukTesting ./nunchukUtility lsinputsUtility input-eventsThe Program
DS1307 OverviewPins X1 and X2Pin SQW/OUTPower3-Volt CompatibilityLogic LevelsTiny RTC ModificationsChecking for Pull-up ResistorsDS1307 Bus SpeedRTC and RAM Address MapReading Date and TimeI2C CommunicationWiringRunning the ExamplesThe Ultimate TestThe Startup Script
Operating ParametersPinoutVS1838B CircuitThe IR ReceiverSoftwareSignal ComponentsCode OrganizationCommand-Line Options
Floppy-Disk Stepper MotorYour Junk-Box Motor?Driver CircuitDarlington PairDriving the DriverInput LevelsPower-on Reset/BootModes of OperationWave Drive (Mode 0)Full-Step Drive (Mode 1)Half-Step Drive (Mode 2)SoftwareTesting
The L298 DriverSensing ResistorEnable A and BInputs In1 and In2Protection DiodesL298 PCBDriving from GPIOThe DMM CheckBipolar Stepper ModesOne-Phase-On ModeTwo-Phase-On ModeHalf-Step ModeChoosing Driving GPIOsProject SchematicJunk-Box MotorsProgram OperationProgram Internals
Switched InputsThe CD4013Testing the Flip-FlopThe LEDØMQPerforming InstallationCompiling and LinkingSensing Station DesignSensing Station ProgramConsole ProgramConsole CommandsSensor Source CodeConsole Source Code
Introduction to PWMPWM ParametersPWM Hardware PeripheralPWM SoftwareMeter Circuitpwm ProgramHardware PWM Set CommandHardware Based CPU Percent-Busy DisplaySoftware PWM ProgramHow Many PWMs?Running the Software PWM CommandSoftware Based CPU Percent-Busy Display
Ohm’s LawPowerUnits

Content preview from Experimenting with Raspberry Pi

CHAPTER 9

Pulse-Width Modulation

This chapter explores pulse-width modulation (PWM) using the Raspberry Pi. PWM is applied in motor control, light dimming, and servo controls, to name a few examples. To keep the hardware simple and the software small enough to read, we’re going to apply PWM to driving an analog meter in this chapter.

While the CPU percent-busy calculation used here is a bit cheesy, it is simple and effective for our demonstration. The meter deflection will indicate how busy your Raspberry Pi’s CPU is. We’ll demonstrate this using a hardware and software PWM solution.

Introduction to PWM

The GPIO output signal is a digital signal ...