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/PwmOut.cpp
- Committer:
- hudakz
- Date:
- 18 months ago
- Revision:
- 1:1f2d9982fa8c
File content as of revision 1:1f2d9982fa8c:
#include "mbed.h" #include "math.h" extern volatile uint32_t *bcm2835_pwm; extern volatile uint32_t *bcm2835_clk; /******************************************************************** * * PwmOut * ********************************************************************/ /** Create a PwmOut connected to the specified pin * * @param pin PwmOut pin to connect to */ PwmOut::PwmOut(PinName pin) : _pwmPin(pin), _duty_cycle(0) { // Set the output pin to Alt Fun 5, to allow PWM channel 0 to be output there bcm2835_gpio_fsel(_pwmPin, BCM2835_GPIO_FSEL_ALT5); // Set default PWM period to 20ms (usually used by servos) period_ms(20); } /** * @brief * @note * @param * @retval */ PwmOut::~PwmOut() { bcm2835_gpio_fsel(_pwmPin, BCM2835_GPIO_FSEL_INPT); } /** Set the output duty-cycle, specified as a percentage (float) * * @param value A floating-point value representing the output duty-cycle, * specified as a percentage. The value should lie between * 0.0f (representing on 0%) and 1.0f (representing on 100%). * Values outside this range will be saturated to 0.0f or 1.0f. */ void PwmOut::write(float value) { _duty_cycle = value; if (value < 0) { _duty_cycle = 0; } if (value > 1.0) { _duty_cycle = 1.0; } bcm2835_pwm_set_data(PWM_CHANNEL, _duty_cycle * _range); bcm2835_pwm_set_mode(PWM_CHANNEL, 1, 1); // channel, MARKSPACE mode, active } /** Return the current output duty-cycle setting, measured as a percentage (float) * * @returns * A floating-point value representing the current duty-cycle being output on the pin, * measured as a percentage. The returned value will lie between * 0.0f (representing on 0%) and 1.0f (representing on 100%). * * @note * This value may not match exactly the value set by a previous write(). */ float PwmOut::read() { return _duty_cycle; } /** Set the PWM period, specified in bcm2835PWMPulseWidth (micro/nano seconds), keeping the duty cycle the same. * @note Sets clock divider according to the required period. * @param period Change the period of a PWM signal. The allowed values are: * BCM2835_PWM_PERIOD_833_NS -> 833.33 ns = 1200.000 kHz */ void PwmOut::period_ms(int period_ms) { _range = period_ms * 1200; bcm2835_pwm_set_clock(BCM2835_PWM_PERIOD_833_NS); // clock pulse = 833.33 ns bcm2835_pwm_set_range(PWM_CHANNEL, _range); } /** Set the PWM period, specified in bcm2835PWMPulseWidth (micro/nano seconds), keeping the duty cycle the same. * @note Sets clock divider according to the required period. * @param period Change the period of a PWM signal. The allowed values are: * BCM2835_PWM_PERIOD_104_NS -> 104.16 ns = 9600.000 kHz */ void PwmOut::period_us(int period_us) { _range = rintf(period_us * 9.600f); bcm2835_pwm_set_clock(BCM2835_PWM_PERIOD_104_NS); bcm2835_pwm_set_range(PWM_CHANNEL, _range); } /*********************************************************************** * * PWM * ***********************************************************************/ /*! Sets the PWM clock divisor, to control the basic PWM pulse widths. \param[in] divisor Divides the basic 19.2MHz PWM clock. You can use one of the common values BCM2835_PWM_CLOCK_DIVIDER_* in \ref bcm2835PWMClockDivider */ void bcm2835_pwm_set_clock(uint32_t divisor) { if (bcm2835_clk == MAP_FAILED || bcm2835_pwm == MAP_FAILED) { return; /* bcm2835_init() failed or not root */ } /* From Gerts code */ divisor &= 0xfff; /* Stop PWM clock */ bcm2835_peri_write(bcm2835_clk + BCM2835_PWMCLK_CNTL, BCM2835_PWM_PASSWRD | 0x01); bcm2835_delay(110); /* Prevents clock going slow */ /* Wait for the clock to be not busy */ while ((bcm2835_peri_read(bcm2835_clk + BCM2835_PWMCLK_CNTL) & 0x80) != 0) bcm2835_delay(1); /* set the clock divider and enable PWM clock */ bcm2835_peri_write(bcm2835_clk + BCM2835_PWMCLK_DIV, BCM2835_PWM_PASSWRD | (divisor << 12)); bcm2835_peri_write(bcm2835_clk + BCM2835_PWMCLK_CNTL, BCM2835_PWM_PASSWRD | 0x11); /* Source=osc and enable */ } /*! Sets the mode of the given PWM channel, allowing you to control the PWM mode and enable/disable that channel \param[in] channel The PWM channel. 0 or 1. \param[in] markspace Set true if you want Mark-Space mode. 0 for Balanced mode. \param[in] enabled Set true to enable this channel and produce PWM pulses. */ void bcm2835_pwm_set_mode(uint8_t channel, uint8_t markspace, uint8_t enabled) { if (bcm2835_clk == MAP_FAILED || bcm2835_pwm == MAP_FAILED) { return; /* bcm2835_init() failed or not root */ } /* If you use the barrier here, wierd things happen, and the commands dont work */ /* uint32_t control = bcm2835_peri_read(bcm2835_pwm + BCM2835_PWM_CONTROL); if (channel == 0) { if (markspace) control |= BCM2835_PWM0_MS_MODE; else control &= ~BCM2835_PWM0_MS_MODE; if (enabled) control |= BCM2835_PWM0_ENABLE; else control &= ~BCM2835_PWM0_ENABLE; } else if (channel == 1) { if (markspace) control |= BCM2835_PWM1_MS_MODE; else control &= ~BCM2835_PWM1_MS_MODE; if (enabled) control |= BCM2835_PWM1_ENABLE; else control &= ~BCM2835_PWM1_ENABLE; } bcm2835_peri_write_nb(bcm2835_pwm + BCM2835_PWM_CONTROL, control); */ bcm2835_peri_write_nb(bcm2835_pwm + BCM2835_PWM_CONTROL, BCM2835_PWM0_ENABLE | BCM2835_PWM1_ENABLE | BCM2835_PWM0_MS_MODE | BCM2835_PWM1_MS_MODE); } /*! Sets the maximum range of the PWM output. The data value can vary between 0 and this range to control PWM output \param[in] channel The PWM channel. 0 or 1. \param[in] range The maximum value permitted for DATA. */ void bcm2835_pwm_set_range(uint8_t channel, uint32_t range) { if (bcm2835_clk == MAP_FAILED || bcm2835_pwm == MAP_FAILED) return; /* bcm2835_init() failed or not root */ if (channel == 0) bcm2835_peri_write_nb(bcm2835_pwm + BCM2835_PWM0_RANGE, range); else if (channel == 1) bcm2835_peri_write_nb(bcm2835_pwm + BCM2835_PWM1_RANGE, range); } /*! Sets the PWM pulse ratio to emit to DATA/RANGE, where RANGE is set by bcm2835_pwm_set_range(). \param[in] channel The PWM channel. 0 or 1. \param[in] data Controls the PWM output ratio as a fraction of the range. Can vary from 0 to RANGE. */ void bcm2835_pwm_set_data(uint8_t channel, uint32_t data) { if (bcm2835_clk == MAP_FAILED || bcm2835_pwm == MAP_FAILED) return; /* bcm2835_init() failed or not root */ if (channel == 0) bcm2835_peri_write_nb(bcm2835_pwm + BCM2835_PWM0_DATA, data); else if (channel == 1) bcm2835_peri_write_nb(bcm2835_pwm + BCM2835_PWM1_DATA, data); }