Zoltan Hudak / mbedPi

mbed API for Raspberry Pi boards.

mbedPi

This is an attempt to implement a limited number of mbed APIs for Raspberry Pi single-board computers. The project was inspired by and based on the arduPi library developed for the Arduino by Cooking Hacks .

/media/uploads/hudakz/board01.jpg

Specifications

  • Chip: Broadcom BCM2836 SoC
  • Core architecture: Quad-core ARM Cortex-A7
  • CPU frequency: 900 MHz
  • GPU: Dual Core VideoCore IV® Multimedia Co-Processor
  • Memory: 1GB LPDDR2
  • Operating System: Boots from Micro SD card, running a version of the Linux operating system
  • Power: Micro USB socket 5V, 2A

Connectors

  • Ethernet: 10/100 BaseT Ethernet socket
  • Video Output: HDMI (rev 1.3 & 1.4)
  • Audio Output: 3.5mm jack, HDMI
  • USB: 4 x USB 2.0 Connector
  • GPIO Connector: 40-pin 2.54 mm (100 mil) expansion header: 2x20 strip providing 27 GPIO pins as well as +3.3 V, +5 V and GND supply lines
  • Camera Connector: 15-pin MIPI Camera Serial Interface (CSI-2)
  • JTAG: Not populated
  • Display Connector: Display Serial Interface (DSI) 15 way flat flex cable connector with two data lanes and a clock lane
  • Memory Card Slot: Micro SDIO

GPIO connector pinout

Zoom in /media/uploads/hudakz/mbedpi_pinout02.png

Information

Only the labels printed in blue/white or green/white (i.e. p3, gpio2 ...) must be used in your code. The other labels are given as information (alternate-functions, power pins, ...).


Building programs for the Raspberry Pi with mbedPi

I use Qt Creator for development, however you can use any other IDE available on the Raspberry Pi (e.g. Geany) if you like. For a quick try:

  • Install Qt and the Qt Creator onto your Raspberry Pi. Then create a new "Blinky" Plain non-Qt C++ Project as follows: /media/uploads/hudakz/newproject.png

  • Change the main code as below:

main.cpp

#include "mbedPi.h"

int main()
{
    DigitalOut  myled(p7);

    while(1) {
        myled = 1; // LED is ON
        wait(0.2); // 200 ms
        myled = 0; // LED is OFF
        wait(1.0); // 1 sec
        printf("Blink\r\n");
    }
}


  • Copy the mbedPi.zip file into your project's folder and unzip.
  • Add the mbedPi.h and mbedPi.cpp files to your project by right clicking on the "Blinky" project and then clicking on the "Add Existing Files..." option in the local menu:

    /media/uploads/hudakz/addfiles.png

    /media/uploads/hudakz/addfiles02.png

  • Double click on Blinky.pro to open it for editing and add new libraries by inserting a new line as follows:

    /media/uploads/hudakz/libs.png

  • Compile the project.

  • Connect an LED through a 1k resistor to pin 7 and the ground on the Raspberry Pi GPIO connector.

  • Run the binary as sudo (sudo ./Blinky) and you should see the LED blinking. /media/uploads/hudakz/mbedpi_run.png

  • Press Ctrl+c to stop running the application.

include/PwmOut.h

Committer:
hudakz
Date:
18 months ago
Revision:
2:131555dc6fb7
Parent:
1:1f2d9982fa8c

File content as of revision 2:131555dc6fb7:

#ifndef _PWM_OUT_H_
#define _PWM_OUT_H_

#include "BCM2835.h"

class PwmOut {

public:

    /** Create a PwmOut connected to the specified pin
     *
     *  @param pin PwmOut pin to connect to
     */
    PwmOut(PinName pin = gpio18);

    ~PwmOut();

    /** Set the output duty-cycle, specified as a percentage (float)
     *
     *  @param value A floating-point value representing the output duty-cycle,
     *    specified as a percentage. The value should lie between
     *    0.0f (representing on 0%) and 1.0f (representing on 100%).
     *    Values outside this range will be saturated to 0.0f or 1.0f.
     */
    void write(float value);

    /** Return the current output duty-cycle setting, measured as a percentage (float)
     *
     *  @returns
     *    A floating-point value representing the current duty-cycle being output on the pin,
     *    measured as a percentage. The returned value will lie between
     *    0.0f (representing on 0%) and 1.0f (representing on 100%).
     *
     *  @note
     *  This value may not match exactly the value set by a previous write().
     */
    float read();

    /** Set the PWM period, specified in bcm2835PWMPulseWidth (micro/nano seconds), keeping the duty cycle the same.
     *  @note  Sets clock divider according to the required period.
     *  @param period Change the period of a PWM signal. The allowed values are:
     *         BCM2835_PWM_PERIOD_212_US  ->  213.33 us  =    4.6875 kHz
     *         BCM2835_PWM_PERIOD_107_US  ->  106.66 us  =    9.375  kHz
     *         BCM2835_PWM_PERIOD_53_US   ->   53.33 us  =   18.75   kHz
     *         BCM2835_PWM_PERIOD_27_US   ->   26.66 us  =   37.50   kHz
     *         BCM2835_PWM_PERIOD_13_US   ->   13.33 us  =   75.00   kHz
     *         BCM2835_PWM_PERIOD_7_US    ->    6.66 us  =  150.00   kHz
     *         BCM2835_PWM_PERIOD_3_US    ->    3.33 us  =  300.00   kHz
     *         BCM2835_PWM_PERIOD_2_US    ->    1.66 us  =  600.00   kHz
     *         BCM2835_PWM_PERIOD_833_NS  ->  833.33 ns  = 1200.00   kHz
     *         BCM2835_PWM_PERIOD_417_NS  ->  416.66 ns  = 2400.00   kHz
     *         BCM2835_PWM_PERIOD_208_NS  ->  208.33 ns  = 4800.00   kHz
     *         BCM2835_PWM_PERIOD_104_NS  ->  104.16 ns  = 9600.00   kHz
     */
    void period_ms(int period);
    void period_us(int period);
    void period_ns(int period);

    /** A operator shorthand for write()
     *  \sa PwmOut::write()
     */
    PwmOut &operator= (float value)
    {
        write(value);
        return *this;
    }

    /** A operator shorthand for write()
     * \sa PwmOut::write()
     */
    PwmOut &operator= (PwmOut &rhs)
    {
        write(rhs.read());
        return *this;
    }

    /** An operator shorthand for read()
     * \sa PwmOut::read()
     */
    operator float()
    {
        return read();
    }

protected:
    PinName     _pwmPin;
    float       _duty_cycle;
    uint32_t    _range;
    uint32_t    _period;
};

#endif	// _PWM_OUT_H_