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 #include "wait.h"
hudakz 1:1f2d9982fa8c 2
hudakz 1:1f2d9982fa8c 3 /**
hudakz 1:1f2d9982fa8c 4 * @brief
hudakz 1:1f2d9982fa8c 5 * @note
hudakz 1:1f2d9982fa8c 6 * @param
hudakz 1:1f2d9982fa8c 7 * @retval
hudakz 1:1f2d9982fa8c 8 */
hudakz 1:1f2d9982fa8c 9 void wait(float s)
hudakz 1:1f2d9982fa8c 10 {
hudakz 1:1f2d9982fa8c 11 unistd::usleep(s * 1000 * 1000);
hudakz 1:1f2d9982fa8c 12 }
hudakz 1:1f2d9982fa8c 13
hudakz 1:1f2d9982fa8c 14 /**
hudakz 1:1f2d9982fa8c 15 * @brief
hudakz 1:1f2d9982fa8c 16 * @note
hudakz 1:1f2d9982fa8c 17 * @param
hudakz 1:1f2d9982fa8c 18 * @retval
hudakz 1:1f2d9982fa8c 19 */
hudakz 1:1f2d9982fa8c 20 void wait_ms(int ms)
hudakz 1:1f2d9982fa8c 21 {
hudakz 1:1f2d9982fa8c 22 unistd::usleep(ms * 1000);
hudakz 1:1f2d9982fa8c 23 }
hudakz 1:1f2d9982fa8c 24
hudakz 1:1f2d9982fa8c 25 /**
hudakz 1:1f2d9982fa8c 26 * @brief
hudakz 1:1f2d9982fa8c 27 * @note
hudakz 1:1f2d9982fa8c 28 * @param
hudakz 1:1f2d9982fa8c 29 * @retval
hudakz 1:1f2d9982fa8c 30 */
hudakz 1:1f2d9982fa8c 31 void wait_us(int us)
hudakz 1:1f2d9982fa8c 32 {
hudakz 1:1f2d9982fa8c 33 if (us > 100) {
hudakz 1:1f2d9982fa8c 34 struct timespec tim, tim2;
hudakz 1:1f2d9982fa8c 35 tim.tv_sec = 0;
hudakz 1:1f2d9982fa8c 36 tim.tv_nsec = us * 1000;
hudakz 1:1f2d9982fa8c 37
hudakz 1:1f2d9982fa8c 38 if (nanosleep(&tim, &tim2) < 0) {
hudakz 1:1f2d9982fa8c 39 fprintf(stderr, "Nano sleep system call failed \n");
hudakz 1:1f2d9982fa8c 40 exit(1);
hudakz 1:1f2d9982fa8c 41 }
hudakz 1:1f2d9982fa8c 42 }
hudakz 1:1f2d9982fa8c 43 else {
hudakz 1:1f2d9982fa8c 44 struct timeval tNow, tLong, tEnd;
hudakz 1:1f2d9982fa8c 45
hudakz 1:1f2d9982fa8c 46 gettimeofday(&tNow, NULL);
hudakz 1:1f2d9982fa8c 47 tLong.tv_sec = us / 1000000;
hudakz 1:1f2d9982fa8c 48 tLong.tv_usec = us % 1000000;
hudakz 1:1f2d9982fa8c 49 timeradd(&tNow, &tLong, &tEnd);
hudakz 1:1f2d9982fa8c 50
hudakz 1:1f2d9982fa8c 51 while (timercmp(&tNow, &tEnd, < ))
hudakz 1:1f2d9982fa8c 52 gettimeofday(&tNow, NULL);
hudakz 1:1f2d9982fa8c 53 }
hudakz 1:1f2d9982fa8c 54 }
hudakz 1:1f2d9982fa8c 55
hudakz 1:1f2d9982fa8c 56 /**
hudakz 1:1f2d9982fa8c 57 * @brief
hudakz 1:1f2d9982fa8c 58 * @note
hudakz 1:1f2d9982fa8c 59 * @param
hudakz 1:1f2d9982fa8c 60 * @retval
hudakz 1:1f2d9982fa8c 61 */
hudakz 1:1f2d9982fa8c 62 uint64_t millis()
hudakz 1:1f2d9982fa8c 63 {
hudakz 1:1f2d9982fa8c 64 return bcm2835_systimer_read() / 1000;
hudakz 1:1f2d9982fa8c 65 }
hudakz 1:1f2d9982fa8c 66
hudakz 1:1f2d9982fa8c 67 /**
hudakz 1:1f2d9982fa8c 68 * @brief
hudakz 1:1f2d9982fa8c 69 * @note
hudakz 1:1f2d9982fa8c 70 * @param
hudakz 1:1f2d9982fa8c 71 * @retval
hudakz 1:1f2d9982fa8c 72 */
hudakz 1:1f2d9982fa8c 73 void bcm2835_delay(unsigned int millis)
hudakz 1:1f2d9982fa8c 74 {
hudakz 1:1f2d9982fa8c 75 struct timespec sleeper;
hudakz 1:1f2d9982fa8c 76
hudakz 1:1f2d9982fa8c 77 sleeper.tv_sec = (time_t) (millis / 1000);
hudakz 1:1f2d9982fa8c 78 sleeper.tv_nsec = (long)(millis % 1000) * 1000000;
hudakz 1:1f2d9982fa8c 79 nanosleep(&sleeper, NULL);
hudakz 1:1f2d9982fa8c 80 }