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.
Committer:
hudakz
Date:
Tue Dec 20 12:16:18 2022 +0000
Revision:
2:131555dc6fb7
Parent:
1:1f2d9982fa8c
Mbed API for Raspberry Pi boards equipped with BCM2836 SoC.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
hudakz 1:1f2d9982fa8c 1 #ifndef _PWM_OUT_H_
hudakz 1:1f2d9982fa8c 2 #define _PWM_OUT_H_
hudakz 1:1f2d9982fa8c 3
hudakz 1:1f2d9982fa8c 4 #include "BCM2835.h"
hudakz 1:1f2d9982fa8c 5
hudakz 1:1f2d9982fa8c 6 class PwmOut {
hudakz 1:1f2d9982fa8c 7
hudakz 1:1f2d9982fa8c 8 public:
hudakz 1:1f2d9982fa8c 9
hudakz 1:1f2d9982fa8c 10 /** Create a PwmOut connected to the specified pin
hudakz 1:1f2d9982fa8c 11 *
hudakz 1:1f2d9982fa8c 12 * @param pin PwmOut pin to connect to
hudakz 1:1f2d9982fa8c 13 */
hudakz 1:1f2d9982fa8c 14 PwmOut(PinName pin = gpio18);
hudakz 1:1f2d9982fa8c 15
hudakz 1:1f2d9982fa8c 16 ~PwmOut();
hudakz 1:1f2d9982fa8c 17
hudakz 1:1f2d9982fa8c 18 /** Set the output duty-cycle, specified as a percentage (float)
hudakz 1:1f2d9982fa8c 19 *
hudakz 1:1f2d9982fa8c 20 * @param value A floating-point value representing the output duty-cycle,
hudakz 1:1f2d9982fa8c 21 * specified as a percentage. The value should lie between
hudakz 1:1f2d9982fa8c 22 * 0.0f (representing on 0%) and 1.0f (representing on 100%).
hudakz 1:1f2d9982fa8c 23 * Values outside this range will be saturated to 0.0f or 1.0f.
hudakz 1:1f2d9982fa8c 24 */
hudakz 1:1f2d9982fa8c 25 void write(float value);
hudakz 1:1f2d9982fa8c 26
hudakz 1:1f2d9982fa8c 27 /** Return the current output duty-cycle setting, measured as a percentage (float)
hudakz 1:1f2d9982fa8c 28 *
hudakz 1:1f2d9982fa8c 29 * @returns
hudakz 1:1f2d9982fa8c 30 * A floating-point value representing the current duty-cycle being output on the pin,
hudakz 1:1f2d9982fa8c 31 * measured as a percentage. The returned value will lie between
hudakz 1:1f2d9982fa8c 32 * 0.0f (representing on 0%) and 1.0f (representing on 100%).
hudakz 1:1f2d9982fa8c 33 *
hudakz 1:1f2d9982fa8c 34 * @note
hudakz 1:1f2d9982fa8c 35 * This value may not match exactly the value set by a previous write().
hudakz 1:1f2d9982fa8c 36 */
hudakz 1:1f2d9982fa8c 37 float read();
hudakz 1:1f2d9982fa8c 38
hudakz 1:1f2d9982fa8c 39 /** Set the PWM period, specified in bcm2835PWMPulseWidth (micro/nano seconds), keeping the duty cycle the same.
hudakz 1:1f2d9982fa8c 40 * @note Sets clock divider according to the required period.
hudakz 1:1f2d9982fa8c 41 * @param period Change the period of a PWM signal. The allowed values are:
hudakz 1:1f2d9982fa8c 42 * BCM2835_PWM_PERIOD_212_US -> 213.33 us = 4.6875 kHz
hudakz 1:1f2d9982fa8c 43 * BCM2835_PWM_PERIOD_107_US -> 106.66 us = 9.375 kHz
hudakz 1:1f2d9982fa8c 44 * BCM2835_PWM_PERIOD_53_US -> 53.33 us = 18.75 kHz
hudakz 1:1f2d9982fa8c 45 * BCM2835_PWM_PERIOD_27_US -> 26.66 us = 37.50 kHz
hudakz 1:1f2d9982fa8c 46 * BCM2835_PWM_PERIOD_13_US -> 13.33 us = 75.00 kHz
hudakz 1:1f2d9982fa8c 47 * BCM2835_PWM_PERIOD_7_US -> 6.66 us = 150.00 kHz
hudakz 1:1f2d9982fa8c 48 * BCM2835_PWM_PERIOD_3_US -> 3.33 us = 300.00 kHz
hudakz 1:1f2d9982fa8c 49 * BCM2835_PWM_PERIOD_2_US -> 1.66 us = 600.00 kHz
hudakz 1:1f2d9982fa8c 50 * BCM2835_PWM_PERIOD_833_NS -> 833.33 ns = 1200.00 kHz
hudakz 1:1f2d9982fa8c 51 * BCM2835_PWM_PERIOD_417_NS -> 416.66 ns = 2400.00 kHz
hudakz 1:1f2d9982fa8c 52 * BCM2835_PWM_PERIOD_208_NS -> 208.33 ns = 4800.00 kHz
hudakz 1:1f2d9982fa8c 53 * BCM2835_PWM_PERIOD_104_NS -> 104.16 ns = 9600.00 kHz
hudakz 1:1f2d9982fa8c 54 */
hudakz 1:1f2d9982fa8c 55 void period_ms(int period);
hudakz 1:1f2d9982fa8c 56 void period_us(int period);
hudakz 1:1f2d9982fa8c 57 void period_ns(int period);
hudakz 1:1f2d9982fa8c 58
hudakz 1:1f2d9982fa8c 59 /** A operator shorthand for write()
hudakz 1:1f2d9982fa8c 60 * \sa PwmOut::write()
hudakz 1:1f2d9982fa8c 61 */
hudakz 1:1f2d9982fa8c 62 PwmOut &operator= (float value)
hudakz 1:1f2d9982fa8c 63 {
hudakz 1:1f2d9982fa8c 64 write(value);
hudakz 1:1f2d9982fa8c 65 return *this;
hudakz 1:1f2d9982fa8c 66 }
hudakz 1:1f2d9982fa8c 67
hudakz 1:1f2d9982fa8c 68 /** A operator shorthand for write()
hudakz 1:1f2d9982fa8c 69 * \sa PwmOut::write()
hudakz 1:1f2d9982fa8c 70 */
hudakz 1:1f2d9982fa8c 71 PwmOut &operator= (PwmOut &rhs)
hudakz 1:1f2d9982fa8c 72 {
hudakz 1:1f2d9982fa8c 73 write(rhs.read());
hudakz 1:1f2d9982fa8c 74 return *this;
hudakz 1:1f2d9982fa8c 75 }
hudakz 1:1f2d9982fa8c 76
hudakz 1:1f2d9982fa8c 77 /** An operator shorthand for read()
hudakz 1:1f2d9982fa8c 78 * \sa PwmOut::read()
hudakz 1:1f2d9982fa8c 79 */
hudakz 1:1f2d9982fa8c 80 operator float()
hudakz 1:1f2d9982fa8c 81 {
hudakz 1:1f2d9982fa8c 82 return read();
hudakz 1:1f2d9982fa8c 83 }
hudakz 1:1f2d9982fa8c 84
hudakz 1:1f2d9982fa8c 85 protected:
hudakz 1:1f2d9982fa8c 86 PinName _pwmPin;
hudakz 1:1f2d9982fa8c 87 float _duty_cycle;
hudakz 1:1f2d9982fa8c 88 uint32_t _range;
hudakz 1:1f2d9982fa8c 89 uint32_t _period;
hudakz 1:1f2d9982fa8c 90 };
hudakz 1:1f2d9982fa8c 91
hudakz 1:1f2d9982fa8c 92 #endif // _PWM_OUT_H_
hudakz 1:1f2d9982fa8c 93