Provided by: libbcm2835-dev_1.71+ds-1_amd64 
NAME
gpio - GPIO register access
SYNOPSIS
Functions
void bcm2835_gpio_fsel (uint8_t pin, uint8_t mode)
void bcm2835_gpio_set (uint8_t pin)
void bcm2835_gpio_clr (uint8_t pin)
void bcm2835_gpio_set_multi (uint32_t mask)
void bcm2835_gpio_clr_multi (uint32_t mask)
uint8_t bcm2835_gpio_lev (uint8_t pin)
uint8_t bcm2835_gpio_eds (uint8_t pin)
uint32_t bcm2835_gpio_eds_multi (uint32_t mask)
void bcm2835_gpio_set_eds (uint8_t pin)
void bcm2835_gpio_set_eds_multi (uint32_t mask)
void bcm2835_gpio_ren (uint8_t pin)
void bcm2835_gpio_clr_ren (uint8_t pin)
void bcm2835_gpio_fen (uint8_t pin)
void bcm2835_gpio_clr_fen (uint8_t pin)
void bcm2835_gpio_hen (uint8_t pin)
void bcm2835_gpio_clr_hen (uint8_t pin)
void bcm2835_gpio_len (uint8_t pin)
void bcm2835_gpio_clr_len (uint8_t pin)
void bcm2835_gpio_aren (uint8_t pin)
void bcm2835_gpio_clr_aren (uint8_t pin)
void bcm2835_gpio_afen (uint8_t pin)
void bcm2835_gpio_clr_afen (uint8_t pin)
void bcm2835_gpio_pud (uint8_t pud)
void bcm2835_gpio_pudclk (uint8_t pin, uint8_t on)
uint32_t bcm2835_gpio_pad (uint8_t group)
void bcm2835_gpio_set_pad (uint8_t group, uint32_t control)
void bcm2835_delay (unsigned int millis)
void bcm2835_delayMicroseconds (uint64_t micros)
void bcm2835_gpio_write (uint8_t pin, uint8_t on)
void bcm2835_gpio_write_multi (uint32_t mask, uint8_t on)
void bcm2835_gpio_write_mask (uint32_t value, uint32_t mask)
void bcm2835_gpio_set_pud (uint8_t pin, uint8_t pud)
uint8_t bcm2835_gpio_get_pud (uint8_t pin)
Detailed Description
These functions allow you to control the GPIO interface. You can set the function of each GPIO pin, read
the input state and set the output state.
Function Documentation
void bcm2835_delay (unsigned int millis)
Delays for the specified number of milliseconds. Uses nanosleep(), and therefore does not use CPU until
the time is up. However, you are at the mercy of nanosleep(). From the manual for nanosleep(): If the
interval specified in req is not an exact multiple of the granularity
underlying clock (see time(7)), then the interval will be rounded up to the next multiple. Furthermore,
after the sleep completes, there may still be a delay before the CPU becomes free to once again execute
the calling thread.
Parameters
millis Delay in milliseconds
void bcm2835_delayMicroseconds (uint64_t micros)
Delays for the specified number of microseconds. Uses a combination of nanosleep() and a busy wait loop
on the BCM2835 system timers, However, you are at the mercy of nanosleep(). From the manual for
nanosleep(): If the interval specified in req is not an exact multiple of the granularity
underlying clock (see time(7)), then the interval will be rounded up to the next multiple. Furthermore,
after the sleep completes, there may still be a delay before the CPU becomes free to once again execute
the calling thread. For times less than about 450 microseconds, uses a busy wait on the System Timer. It
is reported that a delay of 0 microseconds on RaspberryPi will in fact result in a delay of about 80
microseconds. Your mileage may vary.
Parameters
micros Delay in microseconds
void bcm2835_gpio_afen (uint8_t 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.
Parameters
pin GPIO number, or one of RPI_GPIO_P1_* from RPiGPIOPin.
void bcm2835_gpio_aren (uint8_t 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.
Parameters
pin GPIO number, or one of RPI_GPIO_P1_* from RPiGPIOPin.
void bcm2835_gpio_clr (uint8_t pin)
Sets the specified pin output to LOW.
Parameters
pin GPIO number, or one of RPI_GPIO_P1_* from RPiGPIOPin.
See also
bcm2835_gpio_write()
void bcm2835_gpio_clr_afen (uint8_t pin)
Disable Asynchronous Falling Edge Detect Enable for the specified pin.
Parameters
pin GPIO number, or one of RPI_GPIO_P1_* from RPiGPIOPin.
void bcm2835_gpio_clr_aren (uint8_t pin)
Disable Asynchronous Rising Edge Detect Enable for the specified pin.
Parameters
pin GPIO number, or one of RPI_GPIO_P1_* from RPiGPIOPin.
void bcm2835_gpio_clr_fen (uint8_t pin)
Disable Falling Edge Detect Enable for the specified pin.
Parameters
pin GPIO number, or one of RPI_GPIO_P1_* from RPiGPIOPin.
void bcm2835_gpio_clr_hen (uint8_t pin)
Disable High Detect Enable for the specified pin.
Parameters
pin GPIO number, or one of RPI_GPIO_P1_* from RPiGPIOPin.
void bcm2835_gpio_clr_len (uint8_t pin)
Disable Low Detect Enable for the specified pin.
Parameters
pin GPIO number, or one of RPI_GPIO_P1_* from RPiGPIOPin.
void bcm2835_gpio_clr_multi (uint32_t mask)
Sets any of the first 32 GPIO output pins specified in the mask to LOW.
Parameters
mask Mask of pins to affect. Use eg: (1 << RPI_GPIO_P1_03) | (1 << RPI_GPIO_P1_05)
See also
bcm2835_gpio_write_multi()
void bcm2835_gpio_clr_ren (uint8_t pin)
Disable Rising Edge Detect Enable for the specified pin.
Parameters
pin GPIO number, or one of RPI_GPIO_P1_* from RPiGPIOPin.
uint8_t bcm2835_gpio_eds (uint8_t pin)
Event Detect Status. Tests whether the specified pin has detected a level or edge as requested by
bcm2835_gpio_ren(), bcm2835_gpio_fen(), bcm2835_gpio_hen(), bcm2835_gpio_len(), bcm2835_gpio_aren(),
bcm2835_gpio_afen(). Clear the flag for a given pin by calling bcm2835_gpio_set_eds(pin);
Parameters
pin GPIO number, or one of RPI_GPIO_P1_* from RPiGPIOPin.
Returns
HIGH if the event detect status for the given pin is true.
uint32_t bcm2835_gpio_eds_multi (uint32_t mask)
Same as bcm2835_gpio_eds() but checks if any of the pins specified in the mask have detected a level or
edge.
Parameters
mask Mask of pins to check. Use eg: (1 << RPI_GPIO_P1_03) | (1 << RPI_GPIO_P1_05)
Returns
Mask of pins HIGH if the event detect status for the given pin is true.
void bcm2835_gpio_fen (uint8_t 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.
Parameters
pin GPIO number, or one of RPI_GPIO_P1_* from RPiGPIOPin.
void bcm2835_gpio_fsel (uint8_t pin, uint8_t mode)
Sets the Function Select register for the given pin, which configures the pin as Input, Output or one of
the 6 alternate functions.
Parameters
pin GPIO number, or one of RPI_GPIO_P1_* from RPiGPIOPin.
mode Mode to set the pin to, one of BCM2835_GPIO_FSEL_* from bcm2835FunctionSelect
uint8_t bcm2835_gpio_get_pud (uint8_t pin)
On the BCM2711 based RPI 4, gets the current Pull-up/down mode for the specified pin. Returns one of
BCM2835_GPIO_PUD_* from bcm2835PUDControl. On earlier RPI versions not based on the BCM2711, returns
BCM2835_GPIO_PUD_ERROR
Parameters
pin GPIO number, or one of RPI_GPIO_P1_* from RPiGPIOPin.
void bcm2835_gpio_hen (uint8_t pin)
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.
Parameters
pin GPIO number, or one of RPI_GPIO_P1_* from RPiGPIOPin.
void bcm2835_gpio_len (uint8_t 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.
Parameters
pin GPIO number, or one of RPI_GPIO_P1_* from RPiGPIOPin.
uint8_t bcm2835_gpio_lev (uint8_t 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.
Parameters
pin GPIO number, or one of RPI_GPIO_P1_* from RPiGPIOPin.
Returns
the current level either HIGH or LOW
uint32_t bcm2835_gpio_pad (uint8_t group)
Reads and returns the Pad Control for the given GPIO group. Caution: requires root access.
Parameters
group The GPIO pad group number, one of BCM2835_PAD_GROUP_GPIO_*
Returns
Mask of bits from BCM2835_PAD_* from bcm2835PadGroup
void bcm2835_gpio_pud (uint8_t pud)
Sets the Pull-up/down register for the given pin. This is used with bcm2835_gpio_pudclk() to set the
Pull-up/down resistor for the given pin. However, it is usually more convenient to use
bcm2835_gpio_set_pud().
Parameters
pud The desired Pull-up/down mode. One of BCM2835_GPIO_PUD_* from bcm2835PUDControl On the RPI 4,
although this function and bcm2835_gpio_pudclk() are supported for backward compatibility, new code
should always use bcm2835_gpio_set_pud().
See also
bcm2835_gpio_set_pud()
void bcm2835_gpio_pudclk (uint8_t pin, uint8_t on)
Clocks the Pull-up/down value set earlier by bcm2835_gpio_pud() into the pin.
Parameters
pin GPIO number, or one of RPI_GPIO_P1_* from RPiGPIOPin.
on HIGH to clock the value from bcm2835_gpio_pud() into the pin. LOW to remove the clock.
On the RPI 4, although this function and bcm2835_gpio_pud() are supported for backward compatibility, new
code should always use bcm2835_gpio_set_pud().
See also
bcm2835_gpio_set_pud()
void bcm2835_gpio_ren (uint8_t 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.
Parameters
pin GPIO number, or one of RPI_GPIO_P1_* from RPiGPIOPin.
void bcm2835_gpio_set (uint8_t pin)
Sets the specified pin output to HIGH.
Parameters
pin GPIO number, or one of RPI_GPIO_P1_* from RPiGPIOPin.
See also
bcm2835_gpio_write()
void bcm2835_gpio_set_eds (uint8_t 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.
Parameters
pin GPIO number, or one of RPI_GPIO_P1_* from RPiGPIOPin.
void bcm2835_gpio_set_eds_multi (uint32_t mask)
Same as bcm2835_gpio_set_eds() but clears the flag for any pin which is set in the mask.
Parameters
mask Mask of pins to clear. Use eg: (1 << RPI_GPIO_P1_03) | (1 << RPI_GPIO_P1_05)
void bcm2835_gpio_set_multi (uint32_t mask)
Sets any of the first 32 GPIO output pins specified in the mask to HIGH.
Parameters
mask Mask of pins to affect. Use eg: (1 << RPI_GPIO_P1_03) | (1 << RPI_GPIO_P1_05)
See also
bcm2835_gpio_write_multi()
void bcm2835_gpio_set_pad (uint8_t group, uint32_t control)
Sets the Pad Control for the given GPIO group. Caution: requires root access.
Parameters
group The GPIO pad group number, one of BCM2835_PAD_GROUP_GPIO_*
control Mask of bits from BCM2835_PAD_* from bcm2835PadGroup. Note that it is not necessary to
include BCM2835_PAD_PASSWRD in the mask as this is automatically included.
void bcm2835_gpio_set_pud (uint8_t pin, uint8_t pud)
Sets the Pull-up/down mode for the specified pin. This is more convenient than clocking the mode in with
bcm2835_gpio_pud() and bcm2835_gpio_pudclk().
Parameters
pin GPIO number, or one of RPI_GPIO_P1_* from RPiGPIOPin.
pud The desired Pull-up/down mode. One of BCM2835_GPIO_PUD_* from bcm2835PUDControl
void bcm2835_gpio_write (uint8_t pin, uint8_t on)
Sets the output state of the specified pin
Parameters
pin GPIO number, or one of RPI_GPIO_P1_* from RPiGPIOPin.
on HIGH sets the output to HIGH and LOW to LOW.
void bcm2835_gpio_write_mask (uint32_t value, uint32_t mask)
Sets the first 32 GPIO output pins specified in the mask to the value given by value
Parameters
value values required for each bit masked in by mask, eg: (1 << RPI_GPIO_P1_03) | (1 <<
RPI_GPIO_P1_05)
mask Mask of pins to affect. Use eg: (1 << RPI_GPIO_P1_03) | (1 << RPI_GPIO_P1_05)
void bcm2835_gpio_write_multi (uint32_t mask, uint8_t on)
Sets any of the first 32 GPIO output pins specified in the mask to the state given by on
Parameters
mask Mask of pins to affect. Use eg: (1 << RPI_GPIO_P1_03) | (1 << RPI_GPIO_P1_05)
on HIGH sets the output to HIGH and LOW to LOW.
Author
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Version 1.71 Thu Dec 2 2021 gpio(3)