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
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:
- 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:
- 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.
source/gpio.cpp
- Committer:
- hudakz
- Date:
- 21 months ago
- Revision:
- 1:1f2d9982fa8c
File content as of revision 1:1f2d9982fa8c:
#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); } }