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 .

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

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:
  
  
• Change the main code as below:

#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:
  
  
  
  
  
  
• Double click on Blinky.pro to open it for editing and add new libraries by inserting a new line as follows:
  
  
  
  
• 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.
  
  
• Press Ctrl+c to stop running the application.

#include "mbed.h"

/**
 * @brief
 * @note
 * @param
 * @retval
 */
Timer::Timer() :
    _start(0),
    _stop(0),
    _running(false)
{ }

/**
 * @brief
 * @note
 * @param
 * @retval
 */
void Timer::start()
{
    _start = bcm2835_systimer_read();
    _running = true;
}

/**
 * @brief
 * @note
 * @param
 * @retval
 */
void Timer::stop()
{
    _stop = bcm2835_systimer_read();
    _running = false;
}

/**
 * @brief
 * @note
 * @param
 * @retval
 */
void Timer::reset()
{
    _stop = bcm2835_systimer_read();
    _start = _stop;
}

/**
 * @brief
 * @note
 * @param
 * @retval
 */
uint64_t Timer::read_us()
{
    if (_running)
        return(bcm2835_systimer_read() - _start);
    else
        return(_stop - _start);
}

/**
 * @brief
 * @note
 * @param
 * @retval
 */
uint64_t Timer::read_ms()
{
    return read_us() / 1000;
}