GPIO

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Data Types

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gpio_mode

Determines the way in which libsoc handles exporting and unexporting GPIOs in the Linux subsystem.

• LS_GPIO_SHARED

  if the gpio is already exported then it will not unexport the GPIO on free. If it is not exported, then it will unexport on free.

• LS_GPIO_GREEDY

  will succeed if the GPIO is already exported, but will always unexport the GPIO on free.

• LS_GPIO_WEAK

  will fail if GPIO is already exported, will always unexport on free.

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gpio_direction

Used for setting and reading the direction of the GPIO pin.

• DIRECTION_ERROR

  Returned when the GPIO direction could not be read

• INPUT

  GPIO input mode, it's input value can be read

• OUTPUT

  GPIO output mode, it's output value can be written

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gpio_level

Used for setting and reading the level of the GPIO pin.

• LEVEL_ERROR

  Returned when the GPIO level could not be read

• LOW

  GPIO value low, usually logic 0 on the pin, but could be 1 if the gpio is inverted.

• HIGH

  GPIO value high, usually logic 1 on the pin, but could be 0 if the gpio is inverted.

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gpio_edge

Used for setting and reading the edge of the GPIO pin.

• EDGE_ERROR

  Returned when the GPIO edge could not be read

• RISING

  GPIO interrupt is triggered on a rising edge, e.g. logic level 0 followed by 1

• FALLING

  GPIO interrupt is triggered on a falling edge, e.g. logic level 1 followed by 0

• NONE

  GPIO interrupt edge is not set

• BOTH

  GPIO interrupt is triggered on both a falling and rising edge

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gpio_int_ret

Return type for blocked GPIO interrupts.

• LS_INT_ERROR

  Error condition

• LS_INT_TRIGGERED

  Interrupt was triggered

• LS_INT_TIMEOUT

  GPIO poll timedout

Functions

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libsoc_gpio_request

gpio * libsoc_gpio_request(unsigned int gpio_id, gpio_mode mode)

• unsigned int gpio_id

  the Linux ID number for the GPIO you wish to use

• gpio_mode mode

  the mode in which libsoc handles the GPIO file descriptor

Request a GPIO by it's Linux ID number and set the gpio_mode under which libsoc will hold the file descriptor. Returns a malloced gpio struct which will need to be freed by libsoc_gpio_free when no longer needed.

Returns NULL on failure.

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libsoc_gpio_free

int libsoc_gpio_free(gpio * gpio)

• gpioi* gpio

  the previously requested gpio that you wish to release

Free the memory associated with a previously requested GPIO and close the file descriptors.

Returns EXIT_SUCCESS/EXIT_FAILURE

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libsoc_gpio_set_direction

int libsoc_gpio_set_direction(gpio * current_gpio, gpio_direction direction)

• gpio* current_gpio

  requested gpio that you wish to set the direction of

• gpio_direction direction

  direction you wish to set the gpio to

Set the direction of a GPIO, INPUT for reading a GPIO, OUTPUT for setting a GPIO.

Returns EXIT_SUCCESS/EXIT_FAILURE

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libsoc_gpio_get_direction

gpio_direction libsoc_gpio_get_direction(gpio * current_gpio)

• gpio* current_gpio

  requested gpio that you wish to get the direction of

Get the current gpio_direction of a requested GPIO.

Returns gpio_direction, DIRECTION_ERROR on failure, INPUT/OUTPUT on success.

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libsoc_gpio_set_level

int libsoc_gpio_set_level(gpio * current_gpio, gpio_level level)

• gpio * current_gpio

  requested gpio you wish to set the level of

• gpio_level level

  level you wish to set the gpio to

Set the output level of a requested GPIO to HIGH or LOW.

Returns EXIT_SUCCESS/EXIT_FAILURE

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libsoc_gpio_get_level

gpio_level libsoc_gpio_get_level(gpio * current_gpio)

• gpio * current_gpio

  requested gpio you wish to get the level of

Get the current gpio_level of a requested GPIO.

Returns gpio_level, LEVEL_ERROR on failure, LOW/HIGH on success.

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libsoc_gpio_set_edge

int libsoc_gpio_set_edge(gpio * current_gpio, gpio_edge edge)

• gpio * current_gpio

  requested gpio you wish to set the edge of

• gpio_edge edge

  edge you wish to set the gpio to

Set the edge type of a requested GPIO. The edge is the type of signal change that will trigger interrupt detection. See gpio_edge for explanations of the different types of edges and how they work.

Returns EXIT_SUCCESS/EXIT_FAILURE

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libsoc_gpio_get_edge

gpio_edge libsoc_gpio_get_edge(gpio * current_gpio)

• gpio * current_gpio

  requested gpio you wish to get the edge of

Get the current gpio_edge of a requested GPIO.

Returns gpio_edge, EDGE_ERROR on failure, RISING/FALLING/BOTH/NONE on success.

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libsoc_gpio_wait_interrupt

int libsoc_gpio_wait_interrupt(gpio * gpio, int timeout)

• gpio * gpio

  requested gpio you wish to wait for an interrupt on

• int timeout

  the number of seconds to wait for the interrupt, -1 for block indefinitly

Block for a set amount of seconds (or indefinitly) waiting for an interrupt on a GPIO to occur. If you wish to use a non-blocking interrupt mechanism see libsoc_gpio_callback_interrupt.

Returns LS_INT_ERROR on failure, LS_INT_TRIGGERED on captured interrupt, LS_INT_TIMEOUT if no interrupt was captured in the specified time.

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libsoc_gpio_callback_interrupt

int libsoc_gpio_callback_interrupt(gpio * gpio, int (*callback_fn) (void *), void *arg)

• gpio * gpio

  requested gpio you wish to set an interrupt handler for

• int (*callback_fn) (void *) function

  name of the function to use as the interrupt handler. Must match the prototype int* function(void* ptr)

• void * arg

  void casted pointer you wish to be passed to your interrupt handler

Setup an interrupt handler on a GPIO. This will start a new pthread with an infinite poll on the GPIO waiting for the interrupt. When an interrupt is detected the supplied function will run in the thread, and then return to waiting for an interrupt.

Only one interrupt will be queued if it arrives while your supplied function is being run, so it is possible to miss interrupts if they happen too fast.

Returns EXIT_SUCCESS/EXIT_FAILURE

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libsoc_gpio_callback_interrupt_cancel

int libsoc_gpio_callback_interrupt_cancel(gpio * gpio)

• gpio * gpio

  the gpio on which to cancel a waiting interrupt handler

Cancel a previously set interrupt handler on a GPIO. This uses the pthread_cancel function, so it may cancel mid way through your interrupt handler function.

Returns EXIT_SUCCESS/EXIT_FAILURE