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 "BCM2835.h"
hudakz 1:1f2d9982fa8c 2
hudakz 1:1f2d9982fa8c 3 extern volatile uint32_t* bcm2835_st;
hudakz 1:1f2d9982fa8c 4 extern volatile timeval start_program;
hudakz 1:1f2d9982fa8c 5
hudakz 1:1f2d9982fa8c 6 /**
hudakz 1:1f2d9982fa8c 7 * @brief Reads the System Timer Counter (64-bits)
hudakz 1:1f2d9982fa8c 8 * @note
hudakz 1:1f2d9982fa8c 9 * @param
hudakz 1:1f2d9982fa8c 10 * @retval
hudakz 1:1f2d9982fa8c 11 */
hudakz 1:1f2d9982fa8c 12 uint64_t bcm2835_systimer_read(void)
hudakz 1:1f2d9982fa8c 13 {
hudakz 1:1f2d9982fa8c 14 volatile uint32_t* paddr;
hudakz 1:1f2d9982fa8c 15 uint32_t hi, lo;
hudakz 1:1f2d9982fa8c 16 uint64_t st;
hudakz 1:1f2d9982fa8c 17
hudakz 1:1f2d9982fa8c 18 if (bcm2835_st==MAP_FAILED) {
hudakz 1:1f2d9982fa8c 19 return 0;
hudakz 1:1f2d9982fa8c 20 }
hudakz 1:1f2d9982fa8c 21
hudakz 1:1f2d9982fa8c 22 paddr = bcm2835_st + BCM2835_ST_CHI/4;
hudakz 1:1f2d9982fa8c 23 hi = bcm2835_peri_read(paddr);
hudakz 1:1f2d9982fa8c 24
hudakz 1:1f2d9982fa8c 25 paddr = bcm2835_st + BCM2835_ST_CLO/4;
hudakz 1:1f2d9982fa8c 26 lo = bcm2835_peri_read(paddr);
hudakz 1:1f2d9982fa8c 27
hudakz 1:1f2d9982fa8c 28 paddr = bcm2835_st + BCM2835_ST_CHI/4;
hudakz 1:1f2d9982fa8c 29 st = bcm2835_peri_read(paddr);
hudakz 1:1f2d9982fa8c 30
hudakz 1:1f2d9982fa8c 31 /* Test for overflow */
hudakz 1:1f2d9982fa8c 32 if (st == hi)
hudakz 1:1f2d9982fa8c 33 {
hudakz 1:1f2d9982fa8c 34 st <<= 32;
hudakz 1:1f2d9982fa8c 35 st += lo;
hudakz 1:1f2d9982fa8c 36 }
hudakz 1:1f2d9982fa8c 37 else
hudakz 1:1f2d9982fa8c 38 {
hudakz 1:1f2d9982fa8c 39 st <<= 32;
hudakz 1:1f2d9982fa8c 40 paddr = bcm2835_st + BCM2835_ST_CLO/4;
hudakz 1:1f2d9982fa8c 41 st += bcm2835_peri_read(paddr);
hudakz 1:1f2d9982fa8c 42 }
hudakz 1:1f2d9982fa8c 43 return st;
hudakz 1:1f2d9982fa8c 44 }
hudakz 1:1f2d9982fa8c 45
hudakz 1:1f2d9982fa8c 46 /**
hudakz 1:1f2d9982fa8c 47 * @brief
hudakz 1:1f2d9982fa8c 48 * @note
hudakz 1:1f2d9982fa8c 49 * @param
hudakz 1:1f2d9982fa8c 50 * @retval
hudakz 1:1f2d9982fa8c 51 */
hudakz 1:1f2d9982fa8c 52 uint64_t us_ticker_read()
hudakz 1:1f2d9982fa8c 53 {
hudakz 1:1f2d9982fa8c 54 struct timeval end_point;
hudakz 1:1f2d9982fa8c 55 uint64_t elapsedTime;
hudakz 1:1f2d9982fa8c 56
hudakz 1:1f2d9982fa8c 57 // stop timer
hudakz 1:1f2d9982fa8c 58
hudakz 1:1f2d9982fa8c 59 gettimeofday(&end_point, NULL);
hudakz 1:1f2d9982fa8c 60
hudakz 1:1f2d9982fa8c 61 // compute and print the elapsed time in microseconds
hudakz 1:1f2d9982fa8c 62 //elapsedTime = (end_point.tv_sec - start_program.tv_sec) * 1000000.0; // sec to us
hudakz 1:1f2d9982fa8c 63 elapsedTime += (end_point.tv_usec - start_program.tv_usec);
hudakz 1:1f2d9982fa8c 64 return elapsedTime;
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_sleep_for_ms(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 }