NAME

Device::BCM2835 - Perl extension for accesing GPIO pins on a Raspberry Pi via the BCM 2835 GPIO

SYNOPSIS

use Device::BCM2835;
# Library managment
Device::BCM2835::set_debug(1);
Device::BCM2835::init();

# Low level register access
Device::BCM2835::peri_read(&Device::BCM2835::BCM2835_GPIO_BASE + &Device::BCM2835::BCM2835_GPFSEL1);
Device::BCM2835::peri_write(&Device::BCM2835::BCM2835_GPIO_BASE + &Device::BCM2835::BCM2835_GPFSEL2, 0xdeadbeef)
Device::BCM2835::peri_set_bits(&Device::BCM2835::BCM2835_GPIO_BASE + &Device::BCM2835::BCM2835_GPFSEL3, 0xdeadbeef, 0x1f);

# GPIO register access
Device::BCM2835::gpio_fsel(&Device::BCM2835::RPI_GPIO_P1_11, 
  &Device::BCM2835::BCM2835_GPIO_FSEL_OUTP);
Device::BCM2835::gpio_set(&Device::BCM2835::RPI_GPIO_P1_11);
Device::BCM2835::gpio_clr(&Device::BCM2835::RPI_GPIO_P1_11);
Device::BCM2835::gpio_lev(&Device::BCM2835::RPI_GPIO_P1_11);
Device::BCM2835::gpio_eds(&Device::BCM2835::RPI_GPIO_P1_11);
Device::BCM2835::gpio_set_eds(&Device::BCM2835::RPI_GPIO_P1_11);
Device::BCM2835::gpio_ren(&Device::BCM2835::RPI_GPIO_P1_11);
Device::BCM2835::gpio_fen(&Device::BCM2835::RPI_GPIO_P1_11);
Device::BCM2835::gpio_hen(&Device::BCM2835::RPI_GPIO_P1_11);
Device::BCM2835::gpio_len(&Device::BCM2835::RPI_GPIO_P1_11);
Device::BCM2835::gpio_aren(&Device::BCM2835::RPI_GPIO_P1_11);
Device::BCM2835::gpio_afen(&Device::BCM2835::RPI_GPIO_P1_11);
Device::BCM2835::gpio_pud(&Device::BCM2835::BCM2835_GPIO_PUD_OFF);
Device::BCM2835::gpio_pudclk(&Device::BCM2835::RPI_GPIO_P1_11, 1);
my $pad = Device::BCM2835::gpio_pad(&Device::BCM2835::BCM2835_PAD_GROUP_GPIO_0_27);
Device::BCM2835::gpio_set_pad(&Device::BCM2835::BCM2835_PAD_GROUP_GPIO_0_27, 
   &Device::BCM2835::BCM2835_PAD_HYSTERESIS_ENABLED | &Device::BCM2835::BCM2835_PAD_DRIVE_10mA);

# High level and convenience functions
Device::BCM2835::delay(10);
Device::BCM2835::delayMicroseconds(10);
Device::BCM2835::gpio_write(&Device::BCM2835::RPI_GPIO_P1_11, 1);
Device::BCM2835::gpio_set_pud(&Device::BCM2835::RPI_GPIO_P1_11, 
   &Device::BCM2835::BCM2835_GPIO_PUD_UP);

DESCRIPTION

Provides access to GPIO and other IO functions on the Broadcom BCM 2835 chip as used on Raspberry Pi (RPi) http://www.raspberrypi.org

Allows access to the GPIO pins on the 26 pin IDE plug on the RPi board so you can control and interface with various external devices. It provides functions for reading digital inputs and setting digital outputs. Pin event detection is supported by polling (interrupts not supported).

Building this module requires the bcm2835 library to be installed. You can get the latest version from http://www.open.com.au/mikem/bcm2835/

my $ret = Device::BCM2835::init();

Initialise the library by opening /dev/mem and getting pointers to the internal memory for BCM 2835 device registers. You must call this (successfully) before calling any other functions in this library (except Device::BCM2835::set_debug). If Device::BCM2835::init() fails by returning 0, calling any other function may result in crashes or other failures. Prints messages to stderr in case of errors. return 1 if successful else 0

Device::BCM2835::set_debug($debug);

Sets the debug level of the library. A value of 1 prevents mapping to /dev/mem, and makes the library print out what it would do, rather than accessing the GPIO registers. A value of 0, the default, causes nomal operation. Call this before calling Device::BCM2835::init(); debug The new debug level. 1 means debug

my $value = Device::BCM2835::peri_read($paddr);

Reads 32 bit value from a peripheral address The read is done twice, and is therefore always safe in terms of manual section 1.3 Peripheral access precautions for correct memory ordering paddr Physical address to read from. See BCM2835_GPIO_BASE etc. return the value read from the 32 bit register

Device::BCM2835::peri_write($paddr, $value);

Writes 32 bit value from a peripheral address The write is done twice, and is therefore always safe in terms of manual section 1.3 Peripheral access precautions for correct memory ordering paddr Physical address to read from. See BCM2835_GPIO_BASE etc. value The 32 bit value to write

Device::BCM2835::peri_set_bits($paddr, $value, $mask);

Alters a number of bits in a 32 peripheral regsiter. It reads the current valu and then alters the bits deines as 1 in mask, according to the bit value in value. All other bits that are 0 in the mask are unaffected. Use this to alter a subset of the bits in a register. The write is done twice, and is therefore always safe in terms of manual section 1.3 Peripheral access precautions for correct memory ordering paddr Physical address to read from. See BCM2835_GPIO_BASE etc. value The 32 bit value to write, masked in by mask. mask Bitmask that defines the bits that will be altered in the register.

Device::BCM2835::gpio_fsel($pin, $mode);

Sets the Function Select register for the given pin, which configures the pin as Input, Output or one of the 6 alternate functions. pin GPIO number, or one of RPI_GPIO_P1_* from RPiGPIOPin. mode Mode to set the pin to, one of BCM2835_GPIO_FSEL_* from \ref bcm2835FunctionSelect

Device::BCM2835::gpio_set($pin);

Sets the specified pin output to HIGH. See Also Device::BCM2835::gpio_write() pin GPIO number, or one of RPI_GPIO_P1_* from \ref RPiGPIOPin.

Device::BCM2835::gpio_clr($pin);

Sets the specified pin output to LOW. See Also Device::BCM2835::gpio_write() pin GPIO number, or one of RPI_GPIO_P1_* from \ref RPiGPIOPin.

my $value = Device::BCM2835::gpio_lev($pin);

Reads the current level on the specified pin and returns either HIGH or LOW. Works whether or not the pin is an input or an output. pin GPIO number, or one of RPI_GPIO_P1_* from \ref RPiGPIOPin. return the current level either HIGH or LOW

my $value = Device::BCM2835::gpio_eds($pin);

Event Detect Status. Tests whether the specified pin has detected a level or edge as requested by Device::BCM2835::gpio_ren(), Device::BCM2835::gpio_fen(), Device::BCM2835::gpio_hen(), Device::BCM2835::gpio_len(), Device::BCM2835::gpio_aren(), Device::BCM2835::gpio_afen(). Clear the flag for a given pin by calling Device::BCM2835::gpio_set_eds(pin); pin GPIO number, or one of RPI_GPIO_P1_* from \ref RPiGPIOPin. return HIGH if the event detect status for th given pin is true.

Device::BCM2835::gpio_set_eds($pin);

Sets the Event Detect Status register for a given pin to 1, which has the effect of clearing the flag. Use this afer seeing an Event Detect Status on the pin. pin GPIO number, or one of RPI_GPIO_P1_* from \ref RPiGPIOPin.

Device::BCM2835::gpio_ren($pin);

Enable Rising Edge Detect Enable for the specified pin. When a rising edge is detected, sets the appropriate pin in Event Detect Status. The GPRENn registers use synchronous edge detection. This means the input signal is sampled using the system clock and then it is looking for a “011” pattern on the sampled signal. This has the effect of suppressing glitches. pin GPIO number, or one of RPI_GPIO_P1_* from \ref RPiGPIOPin.

Device::BCM2835::gpio_fen($pin);

Enable Falling Edge Detect Enable for the specified pin. When a falling edge is detected, sets the appropriate pin in Event Detect Status. The GPRENn registers use synchronous edge detection. This means the input signal is sampled using the system clock and then it is looking for a “100” pattern on the sampled signal. This has the effect of suppressing glitches. pin GPIO number, or one of RPI_GPIO_P1_* from \ref RPiGPIOPin.

Device::BCM2835::gpio_hen($in);

Enable High Detect Enable for the specified pin. When a HIGH level is detected on the pin, sets the appropriate pin in Event Detect Status. pin GPIO number, or one of RPI_GPIO_P1_* from \ref RPiGPIOPin.

Device::BCM2835::gpio_len($pin);

Enable Low Detect Enable for the specified pin. When a LOW level is detected on the pin, sets the appropriate pin in Event Detect Status. pin GPIO number, or one of RPI_GPIO_P1_* from \ref RPiGPIOPin.

Device::BCM2835::gpio_aren($pin);

Enable Asynchronous Rising Edge Detect Enable for the specified pin. When a rising edge is detected, sets the appropriate pin in Event Detect Status. Asynchronous means the incoming signal is not sampled by the system clock. As such rising edges of very short duration can be detected. pin GPIO number, or one of RPI_GPIO_P1_* from \ref RPiGPIOPin.

Device::BCM2835::gpio_afen($pin);

Enable Asynchronous Falling Edge Detect Enable for the specified pin. When a falling edge is detected, sets the appropriate pin in Event Detect Status. Asynchronous means the incoming signal is not sampled by the system clock. As such falling edges of very short duration can be detected. pin GPIO number, or one of RPI_GPIO_P1_* from \ref RPiGPIOPin.

Device::BCM2835::gpio_pud($pud);

Sets the Pull-up/down register for the given pin. This is used with Device::BCM2835::gpio_pudclk() to set the Pull-up/down resistor for the given pin. However, it is usually more convenient to use Device::BCM2835::gpio_set_pud(). See Also: Device::BCM2835::gpio_set_pud() pud The desired Pull-up/down mode. One of BCM2835_GPIO_PUD_* from bcm2835PUDControl

Device::BCM2835::gpio_pudclk($pin, $on);

Clocks the Pull-up/down value set earlier by Device::BCM2835::gpio_pud() into the pin. See Also: Device::BCM2835::gpio_set_pud() pin GPIO number, or one of RPI_GPIO_P1_* from \ref RPiGPIOPin. on HIGH to clock the value from Device::BCM2835::gpio_pud() into the pin. LOW to remove the clock.

uint32_t Device::BCM2835::gpio_pad($group);

Reads and returns the Pad Control for the given GPIO group. group The GPIO pad group number, one of BCM2835_PAD_GROUP_GPIO_* return Mask of bits from BCM2835_PAD_* from \ref bcm2835PadGroup

Device::BCM2835::gpio_set_pad($group, $control);

Sets the Pad Control for the given GPIO group. group The GPIO pad group number, one of BCM2835_PAD_GROUP_GPIO_* control Mask of bits from BCM2835_PAD_* from \ref bcm2835PadGroup

delay ($millis);

Delays for the specified number of milliseconds. Uses nanosleep(), and therefore does not use CPU until the time is up. millis Delay in milliseconds

delayMicroseconds ($micros);

Delays for the specified number of microseconds. Uses nanosleep(), and therefore does not use CPU until the time is up. micros Delay in microseconds

Device::BCM2835::gpio_write($pin, $on);

Sets the output state of the specified pin pin GPIO number, or one of RPI_GPIO_P1_* from \ref RPiGPIOPin. on HIGH sets the output to HIGH and LOW to LOW.

Device::BCM2835::gpio_set_pud($pin, $pud);

Sets the Pull-up/down mode for the specified pin. This is more convenient than clocking the mode in with Device::BCM2835::gpio_pud() and Device::BCM2835::gpio_pudclk(). pin GPIO number, or one of RPI_GPIO_P1_* from \ref RPiGPIOPin. pud The desired Pull-up/down mode. One of BCM2835_GPIO_PUD_* from bcm2835PUDControl

Example

This simple program blinks RPi GPIO pin 11 every 500ms. It must be run as root, in order to access the BCM 2835 GPIO address space:

use Device::BCM2835;
use strict;

# call set_debug(1) to do a non-destructive test on non-RPi hardware
#Device::BCM2835::set_debug(1);
Device::BCM2835::init() 
 || die "Could not init library";

# Blink pin 11:
# Set RPi pin 11 to be an output
Device::BCM2835::gpio_fsel(&Device::BCM2835::RPI_GPIO_P1_11, 
                           &Device::BCM2835::BCM2835_GPIO_FSEL_OUTP);

while (1)
{
    # Turn it on
    Device::BCM2835::gpio_write(&Device::BCM2835::RPI_GPIO_P1_11, 1);
    Device::BCM2835::delay(500); # Milliseconds
    # Turn it off
    Device::BCM2835::gpio_write(&Device::BCM2835::RPI_GPIO_P1_11, 0);
    Device::BCM2835::delay(500); # Milliseconds
}

EXPORT

None by default.

Exportable constants

BCM2835_BLOCK_SIZE
BCM2835_CLOCK_BASE
BCM2835_GPAFEN0
BCM2835_GPAFEN1
BCM2835_GPAREN0
BCM2835_GPAREN1
BCM2835_GPCLR0
BCM2835_GPCLR1
BCM2835_GPEDS0
BCM2835_GPEDS1
BCM2835_GPFEN0
BCM2835_GPFEN1
BCM2835_GPFSEL0
BCM2835_GPFSEL1
BCM2835_GPFSEL2
BCM2835_GPFSEL3
BCM2835_GPFSEL4
BCM2835_GPFSEL5
BCM2835_GPHEN0
BCM2835_GPHEN1
BCM2835_GPIO_BASE
BCM2835_GPIO_FSEL_ALT0
BCM2835_GPIO_FSEL_ALT1
BCM2835_GPIO_FSEL_ALT2
BCM2835_GPIO_FSEL_ALT3
BCM2835_GPIO_FSEL_ALT4
BCM2835_GPIO_FSEL_ALT5
BCM2835_GPIO_FSEL_INPT
BCM2835_GPIO_FSEL_MASK
BCM2835_GPIO_FSEL_OUTP
BCM2835_GPIO_PADS
BCM2835_GPIO_PUD_DOWN
BCM2835_GPIO_PUD_OFF
BCM2835_GPIO_PUD_UP
BCM2835_GPIO_PWM
BCM2835_GPLEN0
BCM2835_GPLEN1
BCM2835_GPLEV0
BCM2835_GPLEV1
BCM2835_GPPUD
BCM2835_GPPUDCLK0
BCM2835_GPPUDCLK1
BCM2835_GPREN0
BCM2835_GPREN1
BCM2835_GPSET0
BCM2835_GPSET1
BCM2835_PADS_GPIO_0_27
BCM2835_PADS_GPIO_28_45
BCM2835_PADS_GPIO_46_53
BCM2835_PAD_DRIVE_10mA
BCM2835_PAD_DRIVE_12mA
BCM2835_PAD_DRIVE_14mA
BCM2835_PAD_DRIVE_16mA
BCM2835_PAD_DRIVE_2mA
BCM2835_PAD_DRIVE_4mA
BCM2835_PAD_DRIVE_6mA
BCM2835_PAD_DRIVE_8mA
BCM2835_PAD_GROUP_GPIO_0_27
BCM2835_PAD_GROUP_GPIO_28_45
BCM2835_PAD_GROUP_GPIO_46_53
BCM2835_PAD_HYSTERESIS_ENABLED
BCM2835_PAD_SLEW_RATE_UNLIMITED
BCM2835_PAGE_SIZE
BCM2835_PERI_BASE
BCM2835_PWM0_DATA
BCM2835_PWM0_ENABLE
BCM2835_PWM0_MS_MODE
BCM2835_PWM0_OFFSTATE
BCM2835_PWM0_RANGE
BCM2835_PWM0_REPEATFF
BCM2835_PWM0_REVPOLAR
BCM2835_PWM0_SERIAL
BCM2835_PWM0_USEFIFO
BCM2835_PWM1_DATA
BCM2835_PWM1_ENABLE
BCM2835_PWM1_MS_MODE
BCM2835_PWM1_OFFSTATE
BCM2835_PWM1_RANGE
BCM2835_PWM1_REPEATFF
BCM2835_PWM1_REVPOLAR
BCM2835_PWM1_SERIAL
BCM2835_PWM1_USEFIFO
BCM2835_PWMCLK_CNTL
BCM2835_PWMCLK_DIV
BCM2835_PWM_CONTROL
BCM2835_PWM_STATUS
HIGH
LOW
RPI_GPIO_P1_03
RPI_GPIO_P1_05
RPI_GPIO_P1_07
RPI_GPIO_P1_08
RPI_GPIO_P1_10
RPI_GPIO_P1_11
RPI_GPIO_P1_12
RPI_GPIO_P1_13
RPI_GPIO_P1_15
RPI_GPIO_P1_16
RPI_GPIO_P1_18
RPI_GPIO_P1_19
RPI_GPIO_P1_21
RPI_GPIO_P1_22
RPI_GPIO_P1_23
RPI_GPIO_P1_24
RPI_GPIO_P1_26

SEE ALSO

You will need to familiar with the GPIO pinouts etc:

http://elinux.org/RPi_Low-level_peripherals http://www.raspberrypi.org/wp-content/uploads/2012/02/BCM2835-ARM-Peripherals.pdf http://www.open.com.au/mikem/bcm2835

AUTHOR

Mike McCauley, <mikem@open.com.au>

COPYRIGHT AND LICENSE

Copyright (C) 2012 by Mike McCauley

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.14.2 or, at your option, any later version of Perl 5 you may have available.