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.

source/gpio.cpp

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

File content as of revision 2:131555dc6fb7:

#include "mbed.h"

extern struct bcm2835_peripheral   gpio;

/********** FUNCTIONS OUTSIDE CLASSES **********/

// Write a HIGH or a LOW value to a digital pin
void gpio_write(PinName pin, int value)
{
    if (value == HIGH)
        GPSET0 = (1 << pin);
    else
    if (value == LOW)
        GPCLR0 = (1 << pin);

    wait_us(1); // Delay to allow any change in state to be reflected in the LEVn, register bit.
}

// Reads the value from a specified digital pin, either HIGH or LOW.
int gpio_read(PinName pin)
{
    Digivalue   value;
    if (GPLEV0 & (1 << pin))
        value = HIGH;
    else
        value = LOW;

    return value;
}

// Function select
// pin is a BCM2835 GPIO pin number NOT RPi pin number
//      There are 6 control registers, each control the functions of a block
//      of 10 pins.
//      Each control register has 10 sets of 3 bits per GPIO pin:
//
//      000 = GPIO Pin X is an input
//      001 = GPIO Pin X is an output
//      100 = GPIO Pin X takes alternate function 0
//      101 = GPIO Pin X takes alternate function 1
//      110 = GPIO Pin X takes alternate function 2
//      111 = GPIO Pin X takes alternate function 3
//      011 = GPIO Pin X takes alternate function 4
//      010 = GPIO Pin X takes alternate function 5
//
// So the 3 bits for port X are:

//      X / 10 + ((X % 10) * 3)

void bcm2835_gpio_fsel(uint8_t pin, uint8_t mode)
{
    // Function selects are 10 pins per 32 bit word, 3 bits per pin
    volatile uint32_t*  paddr = (volatile uint32_t*)gpio.map + BCM2835_GPFSEL0 / 4 + (pin / 10);
    uint8_t             shift = (pin % 10) * 3;
    uint32_t            mask = BCM2835_GPIO_FSEL_MASK << shift;
    uint32_t            value = mode << shift;

    bcm2835_peri_set_bits(paddr, value, mask);
}

/**
 * @brief
 * @note
 * @param
 * @retval
 */
void gpio_dir(PinName pin, PinDirection direction)
{
    uint8_t     gpfsel = pin / 10;
    uint8_t     shift = (pin % 10) * 3;
    uint32_t    mask = BCM2835_GPIO_FSEL_MASK << shift;
    uint32_t    outp = BCM2835_GPIO_FSEL_OUTP << shift;

    if (direction == PIN_OUTPUT) {
        *(gpio.addr + gpfsel) &= ~mask;
        *(gpio.addr + gpfsel) |= outp;
    }
    else
    if (direction == PIN_INPUT) {
        *(gpio.addr + gpfsel) &= ~mask;
    }
}

/**
 * @brief
 * @note
 * @param
 * @retval
 */
void gpio_mode(PinName pin, PinMode mode)
{
    mode == PullUp ? gpio_write(pin, HIGH) : gpio_write(pin, LOW);
}

/**
 * @brief
 * @note
 * @param
 * @retval
 */
uint8_t shiftIn(PinName dPin, PinName cPin, bcm2835SPIBitOrder order)
{
    uint8_t value = 0;
    int8_t  i;

    if (order == MSBFIRST)
        for (i = 7; i >= 0; --i) {
            gpio_write(cPin, HIGH);
            value |= gpio_read(dPin) << i;
            gpio_write(cPin, LOW);
        }
    else
        for (i = 0; i < 8; ++i) {
            gpio_write(cPin, HIGH);
            value |= gpio_read(dPin) << i;
            gpio_write(cPin, LOW);
        }

    return value;
}

/**
 * @brief
 * @note
 * @param
 * @retval
 */
void shiftOut(PinName dPin, PinName cPin, bcm2835SPIBitOrder order, uint8_t val)
{
    int8_t  i;

    if (order == MSBFIRST)
        for (i = 7; i >= 0; --i) {
            gpio_write(dPin, val & (1 << i));
            gpio_write(cPin, HIGH);
            gpio_write(cPin, LOW);
        }
    else
        for (i = 0; i < 8; ++i) {
            gpio_write(dPin, val & (1 << i));
            gpio_write(cPin, HIGH);
            gpio_write(cPin, LOW);
        }
}