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 "BCM2835.h"

extern volatile uint32_t*   bcm2835_st;
extern volatile timeval     start_program;

/**
 * @brief   Reads the System Timer Counter (64-bits)
 * @note
 * @param
 * @retval
 */
uint64_t bcm2835_systimer_read(void)
{
    volatile uint32_t* paddr;
    uint32_t hi, lo;
    uint64_t st;

    if (bcm2835_st==MAP_FAILED) {
        return 0;
    }

    paddr = bcm2835_st + BCM2835_ST_CHI/4;
    hi = bcm2835_peri_read(paddr);

    paddr = bcm2835_st + BCM2835_ST_CLO/4;
    lo = bcm2835_peri_read(paddr);

    paddr = bcm2835_st + BCM2835_ST_CHI/4;
    st = bcm2835_peri_read(paddr);

    /* Test for overflow */
    if (st == hi)
    {
        st <<= 32;
        st += lo;
    }
    else
    {
        st <<= 32;
        paddr = bcm2835_st + BCM2835_ST_CLO/4;
        st += bcm2835_peri_read(paddr);
    }
    return st;
}

/**
 * @brief
 * @note
 * @param
 * @retval
 */
uint64_t us_ticker_read()
{
    struct timeval  end_point;
    uint64_t        elapsedTime;

    // stop timer

    gettimeofday(&end_point, NULL);

    // compute and print the elapsed time in microseconds
    //elapsedTime = (end_point.tv_sec - start_program.tv_sec) * 1000000.0;   // sec to us
    elapsedTime += (end_point.tv_usec - start_program.tv_usec);
    return elapsedTime;
}

/**
 * @brief
 * @note
 * @param
 * @retval
 */
void bcm2835_sleep_for_ms(unsigned int millis)
{
    struct timespec sleeper;

    sleeper.tv_sec = (time_t) (millis / 1000);
    sleeper.tv_nsec = (long)(millis % 1000) * 1000000;
    nanosleep(&sleeper, NULL);
}