raspberry-pi-gpio

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Overview

Library for Raspberry Pi GPIO.

• Clock Generator Library (rpi_clkgen.c, rpi_clkgen.h)
• GPIO Library (rpi_gpio.c, rpi_gpio.h)
• I2C Library (rpi_i2c.c, rpi_i2c.h)
• SPI Library (rpi_spi.c, rpi_spi.h)
• Register Map Library (rpi_regmap.c, rpi_regmap.h)

Clock Generator Library

Preparation

Not necessary.

Usage

Sample code to enable clock generator:

#include "rpi_clkgen.h"

int main(void)
{
	/* output 1HMz clock on GPIO-4 (1GHz / 1000) */
	rpiClkgenEnable(4U, D_RPI_CMGPCTL_MASH_INT, D_RPI_CMGPCTL_SRC_PLLC, 1000U, 0U);

	return 0;
}

Sample code to disable clock generator:

#include "rpi_clkgen.h"

int main(void)
{
	/* disable clock on GPIO-4 */
	rpiClkgenDisable(4U);

	return 0;
}

Clock frequency of each clock sources:

Clock Source	Parameter	Frequency (BCM2837)
GND	D_RPI_CMGPCTL_SRC_GND	0 Hz
oscillator	D_RPI_CMGPCTL_SRC_OSC	19.2 MHz
testdebug0	D_RPI_CMGPCTL_SRC_DBG0	0 Hz
testdebug1	D_RPI_CMGPCTL_SRC_DBG1	0 Hz
PLLA per	D_RPI_CMGPCTL_SRC_PLLA	0 Hz
PLLC per	D_RPI_CMGPCTL_SRC_PLLC	1 GHz
PLLD per	D_RPI_CMGPCTL_SRC_PLLD	500 MHz
HDMI auxiliary	D_RPI_CMGPCTL_SRC_HDMI	0 Hz

GPIO pins that can be used as a clock source:

GPIO-4, GPIO-5, GPIO-6, GPIO-20, GPIO-21, GPIO-32, GPIO-34, GPIO-42, GPIO-43, GPIO-44

GPIO Library

Preparation

Not necessary.

Usage

Sample code to use GPIO library for an output port:

#include "rpi_gpio.h"

int main(void)
{
	/* open GPIO-4 as an output port */
	rpiGpioOpenOut(4);

	/*
	 * The following GPIO libraries are available here.
	 *   - int8_t rpiGpioSet(uint8_t pin);
	 *   - int8_t rpiGpioClr(uint8_t pin);
	 *   - int8_t rpiGpioGet(uint8_t pin, int32_t *val);
	 */
	...

	/* close GPIO-4 */
	rpiGpioClose(4);

	return 0;
}

Sample code to use GPIO library for an input port:

#include "rpi_gpio.h"

int main(void)
{
	/* open GPIO-5 as an input port */
	rpiGpioOpenIn(5);

	/*
	 * The following GPIO libraries are available here.
	 *   - int8_t rpiGpioGet(uint8_t pin, int32_t *val);
	 */
	...

	/* close GPIO-5 */
	rpiGpioClose(5);

	return 0;
}

I2C Library

Preparation

Enable I2C device driver:

$ sudo raspi-config

Select [7 Advanced Options] > [A7 I2C] > [Yes].

You can discover device drivers at /dev:

$ ls /dev | grep i2c

Usage

Sample code to use I2C library:

#include "rpi_i2c.h"

#define BUF_SIZE	(8)

int main(void)
{
	uint8_t cmd, data;
	uint8_t tx_data[BUF_SIZE];
	uint8_t rx_data[BUF_SIZE];

	/* open SPI port */
	rpiI2cOpen("/dev/i2c-1");

	/* set slave address (0x12) */
	rpiI2cSetSlave(0x12U);

	/* write data */
	cmd = ...;
	data = ...;
	rpiI2cWrite(cmd, &data);

	/* read data */
	cmd = ...;
	rpiI2cRead(cmd, &data);

	/* write block data */
	cmd = ...;
	tx_data[0] = ...;
	tx_data[1] = ...;
	...
	tx_data[7] = ...;
	rpiI2cWriteBlock(cmd, tx_data, BUF_SIZE);

	/* read block data */
	cmd = ...;
	rpiI2cReadBlock(cmd, rx_data, BUF_SIZE);

	/* close I2C port */
	rpiI2cClose();

	return 0;
}

SPI Library

Preparation

Enable SPI device driver:

$ sudo raspi-config

Select [7 Advanced Options] > [A6 SPI] > [Yes].

You can discover device drivers at /dev:

$ ls /dev | grep spi

Usage

Sample code to use SPI library:

#include "rpi_spi.h"

#define BUF_SIZE	(8)

int main(void)
{
	uint8_t tx_data[BUF_SIZE];
	uint8_t rx_data[BUF_SIZE];

	/* open SPI port */
	rpiSpiOpen("/dev/spidev0.0");

	/* set SPI mode (CPOL: positive logic, CPHA: positive edge) */
	rpiSpiSetMode(SPI_MODE_0);

	/* set transfer speed (2MHz) */
	rpiSpiSetSpeed(2000000UL);

	/* set transfer delay time (10usec)*/
	rpiSpiSetDelay(10U);

	/* set bits per word (8bit) */
	rpiSpiSetBitsPerWord(8U);

	/* set CS polarity (negative logic) */
	rpiSpiSetCsPolarity(D_SPI_CS_NEG_LOGIC);

	/* transfer data */
	tx_data[0] = ...;
	tx_data[1] = ...;
	...
	tx_data[7] = ...;
	rpiSpiTransfer(tx_data, rx_data, BUF_SIZE);

	/* close SPI port */
	rpiSpiClose();

	return 0;
}

Register Map Library

Preparation

Not necessary.

Usage

Sample code to use register map library:

#include "rpi_regmap.h"

int main(void)
{
	/* initialize register map library */
	rpiRegmapInit();

	/*
	 * The following GPIO libraries, rpiRegmapSet***() and rpiRegmapGet***(), are available here.
	 * [Setter functions]
	 *   - void rpiRegmapSetGpfselFsel(uint8_t pin, uint32_t fsel);
	 *   - void rpiRegmapSetCmGpctlMash(uint8_t ch, uint32_t mash);
	 *   - void rpiRegmapSetCmGpctlEnab(uint8_t ch, uint32_t enab);
	 *   - void rpiRegmapSetCmGpctlSrc(uint8_t ch, uint32_t src);
	 *   - void rpiRegmapSetCmGpdivDivi(uint8_t ch, uint32_t divi);
	 *   - void rpiRegmapSetCmGpdivDivf(uint8_t ch, uint32_t divf);
	 * [Getter functions]
	 *   - uint32_t rpiRegmapGetGpfselFsel(uint8_t pin);
	 *   - uint32_t rpiRegmapGetCmGpctlMash(uint8_t ch);
	 *   - uint32_t rpiRegmapGetCmGpctlBusy(uint8_t ch);
	 *   - uint32_t rpiRegmapGetCmGpctlEnab(uint8_t ch);
	 *   - uint32_t rpiRegmapGetCmGpctlSrc(uint8_t ch);
	 *   - uint32_t rpiRegmapGetCmGpdivDivi(uint8_t ch);
	 *   - uint32_t rpiRegmapGetCmGpdivDivf(uint8_t ch);
	 */
	...

	/* finalize register map library */
	rpiRegmapFinal();

	return 0;
}

For more details of libraries and SoC registers, refer to the documentation introduced in the Documentation section and hardware manual.

[Attention] The Above hardware manual is written for Raspberry Pi 1 (BCM2835). Note that the base address of the peripheral register is different on Raspberry Pi 2 (BCM2836) and Raspberry Pi 3 (BCM2837). If you want to use my register map library on Raspberry Pi 1, you must change the value of D_RPI_BASE_GPIO and D_RPI_BASE_CM as below.

Raspberry Pi	SoC	Base Address	D_RPI_BASE_GPIO	D_RPI_BASE_CM
Raspberry Pi 1	BCM2835	0x20000000	0x20200000	0x20101000
Raspberry Pi 2	BCM2836	0x3F000000	0x3F200000	0x3F101000
Raspberry Pi 3	BCM2837	0x3F000000	0x3F200000	0x3F101000

Documentation

Install tools to generate documentation:

$ sudo apt-get install doxygen graphviz texlive-full

Make html based documentation (./doc/html/index.html):

$ make doc

Make pdf based documentation (./doc/latex/refman.pdf):

$ cd doc/latex
$ make

License

MIT

Author

T. Ngtk