cl gpio

Table of Contents

About cl-gpio

This is a bindings library for the Linux GPIO kernel module as described on https://www.kernel.org/doc/Documentation/gpio/sysfs.txt. It provides both primitive access and more sophisticated constructs to work with interrupts and such.

How To

Enumerate a list of all available GPIO pins on your system:

(gpio:pins)

If you have GPIO pins on your system and GPIO:PINS returns NIL, then try to export them first:

;; Replace 26 with how many pins you have:
(loop for i from 0 to 26
      do (gpio:export i))

GPIO:PINS should now return the pins' statuses:

(gpio:pins) =>

(#<CL-GPIO:PIN 0 :OUT> #<CL-GPIO:PIN 1 :IN> #<CL-GPIO:PIN 10 :IN>
#<CL-GPIO:PIN 11 :IN> #<CL-GPIO:PIN 12 :IN> #<CL-GPIO:PIN 13 :IN>
#<CL-GPIO:PIN 14 :IN> #<CL-GPIO:PIN 15 :IN> #<CL-GPIO:PIN 16 :IN>
#<CL-GPIO:PIN 17 :IN> #<CL-GPIO:PIN 18 :IN> #<CL-GPIO:PIN 19 :IN>
#<CL-GPIO:PIN 2 :IN> #<CL-GPIO:PIN 20 :IN> #<CL-GPIO:PIN 21 :IN>
#<CL-GPIO:PIN 22 :IN> #<CL-GPIO:PIN 23 :IN> #<CL-GPIO:PIN 24 :IN>
#<CL-GPIO:PIN 25 :IN> #<CL-GPIO:PIN 26 :IN> #<CL-GPIO:PIN 3 :IN>
#<CL-GPIO:PIN 4 :IN> #<CL-GPIO:PIN 5 :IN> #<CL-GPIO:PIN 6 :IN>
#<CL-GPIO:PIN 7 :IN> #<CL-GPIO:PIN 8 :IN> #<CL-GPIO:PIN 9 :IN>)

You can then access the direction, edge, and active-low of each pin:

(setf (gpio:direction 0) :out)
(gpio:active-low 0)

If you try to read or set a PIN's value, its direction is automatically adjusted as necessary:

(gpio:value 0)
(setf (gpio:value 0) T)

On SBCL you can also wait for values:

(progn (gpio:await-value 0)
       (format T "Whoah, 0's edge is ~a to ~:[0~;1~]" (edge 0) (value 0)))

Or even install handlers:

(defun pin-value-handler (pin value)
  (format T "~& ~a changed value to ~a." pin value))
(gpio:with-pin-handler (#'pin-value-handler 0 :falling)
  (format T "Waiting for a change on 0...")
  (loop (sleep 0.001)))

Naturally you'll have to refer to your particular board/system's specification to be able to tell which pins are supposed to be used for what. For the Raspberry Pi 2/3/4, it would be:

(Source)

System Information

Definition Index

• CL-GPIO

  • ORG.SHIRAKUMO.GPIO
  • GPIO

  No documentation provided.

  • EXTERNAL STRUCTURE

    PIN

    Source

    Representative type to encapsulate a GPIO pin.
    
    This will cache current pin properties. Note that it will
    not be updated automatically should changes to the pin
    occur from elsewhere in the system. Only updates done
    through this high-level interface will be tracked.
    
    See MAKE-PIN
    See ENSURE-PIN
    See NAME
    See CHIP
    See DIRECTION
    See EDGE
    See ACTIVE-LOW
    See VALUE

  • EXTERNAL FUNCTION

    ACTIVE-LOW

    • PIN
    • &REST

    Source

    Accesses the pin's I/O active-low.
    
    If the pin does not yet exist or is not exported, it will be.
    The system GPIO's value is not adjusted if the cached value
    is already the same as the value attempted to be set with this.
    
    See ENSURE-PIN
    See CL-GPIO-LLI:ACTIVE-LOW
    See PIN-ACTIVE-LOW

  • EXTERNAL FUNCTION

    (SETF ACTIVE-LOW)

    • ACTIVE-LOW
    • PIN
    • &REST

    Source

    No documentation provided.
  • EXTERNAL FUNCTION

    ALL-PINS

    Source

    Returns a list of PIN instances for all pins on the system.
    
    See CL-GPIO-LLI:AVAILABLE-PINS
    See ENSURE-PIN

  • EXTERNAL FUNCTION

    AWAIT-VALUE

    • PIN
    • &OPTIONAL
    • TIMEOUT
    • &REST

    Source

    Wait until the pin has a value that we can read.
    
    If TIMEOUT is specified and reached before a value becomes
    accessible, NIL is returned. Otherwise, true is returned.
    
    This function is available on the following implementations:
     * SBCL
    
    See ENSURE-PIN

  • EXTERNAL FUNCTION

    CALL-WITH-PIN-HANDLER

    • FUNCTION
    • HANDLER
    • PIN
    • &OPTIONAL
    • EDGE
    • ACTIVE-LOW
    • &REST

    Source

    Make the HANDLER function be called if the PIN changes value during the evaluation of FUNCTION.
    
    The HANDLER is called with the corresponding PIN instance
    and the new value as arguments.
    
    This function is available on the following implementations:
     * SBCL
    
    See ENSURE-PIN
    See EDGE
    See ACTIVE-LOW

  • EXTERNAL FUNCTION

    CHIP

    • PIN
    • &REST

    Source

    Returns the pin's chip device name.
    
    See PIN-CHIP

  • EXTERNAL FUNCTION

    DIRECTION

    • PIN
    • &REST

    Source

    Accesses the pin's I/O direction.
    
    If the pin does not yet exist or is not exported, it will be.
    The system GPIO's value is not adjusted if the cached value
    is already the same as the value attempted to be set with this.
    
    See ENSURE-PIN
    See CL-GPIO-LLI:DIRECTION
    See PIN-DIRECTION

  • EXTERNAL FUNCTION

    (SETF DIRECTION)

    • DIRECTION
    • PIN
    • &REST

    Source

    No documentation provided.
  • EXTERNAL FUNCTION

    EDGE

    • PIN
    • &REST

    Source

    Accesses the pin's I/O edge.
    
    If the pin does not yet exist or is not exported, it will be.
    The system GPIO's value is not adjusted if the cached value
    is already the same as the value attempted to be set with this.
    
    See ENSURE-PIN
    See CL-GPIO-LLI:EDGE
    See PIN-EDGE

  • EXTERNAL FUNCTION

    (SETF EDGE)

    • EDGE
    • PIN
    • &REST

    Source

    No documentation provided.
  • EXTERNAL FUNCTION

    ENSURE-PIN

    • PIN
    • &OPTIONAL
    • REFRESH
    • &REST

    Source

    Ensure to get a PIN instance in return.
    
    Accepts either a pin's name/id number or a pin instance.
    If REFRESH is true, a fresh PIN instance is returned
    that has its values taken from the system's GPIO values.
    
    See *PIN-CACHE*
    See MAKE-PIN
    See PIN

  • EXTERNAL FUNCTION

    EXPORT

    • &REST
    • PINS
    • &REST

    Source

    Export the specified pins and return a list of according PIN instances.
    
    See ENSURE-PIN
    See CL-GPIO-LLI:EXPORT-PIN

  • EXTERNAL FUNCTION

    NAME

    • PIN
    • &REST

    Source

    Returns the pin's name or ID.
    
    See PIN-NAME

  • EXTERNAL FUNCTION

    PINS

    Source

    Returns a list of available/exported PIN instances.
    
    See CL-GPIO-LLI:EXPORTED-PINS
    See ENSURE-PIN

  • EXTERNAL FUNCTION

    UNEXPORT

    • &REST
    • PINS
    • &REST

    Source

    Unexport the specified pins and invalidate their cache.
    
    See *PIN-CACHE*
    See CL-GPIO-LLI:UNEXPORT-PIN

  • EXTERNAL FUNCTION

    VALUE

    • PIN
    • &REST

    Source

    Accesses the pin's I/O value.
    
    If the pin does not yet exist or is not exported, it will be.
    The pin's I/O direction is automatically adjusted if necessary
    depending on whether the value is read or set by setf.
    The value returned by this is never cached.
    
    See ENSURE-PIN
    See CL-GPIO-LLI:VALUE

  • EXTERNAL FUNCTION

    (SETF VALUE)

    • VALUE
    • PIN
    • &REST

    Source

    No documentation provided.
  • EXTERNAL MACRO

    WITH-PIN-HANDLER

    • HANDLER
    • PIN
    • &OPTIONAL
    • EDGE
    • ACTIVE-LOW
    • &REST
    • &BODY
    • BODY
    • &REST

    Source

    Shorthand to call a handler function on PIN value change during the evaluation of BODY.
    
    See CALL-WITH-PIN-HANDLER

• CL-GPIO-LLI

  • ORG.SHIRAKUMO.GPIO.LLI

  No documentation provided.

  • EXTERNAL SPECIAL-VARIABLE

    *GPIO-ROOT*

    Source

    The root directory of the GPIO system devices.
    Should be /sys/class/gpio/

  • EXTERNAL FUNCTION

    ACTIVE-LOW

    • PIN
    • &REST

    Source

    Accessor to whether the GPIO pin has an active low.
    
    The value should be either NIL or T.

  • EXTERNAL FUNCTION

    (SETF ACTIVE-LOW)

    • VALUE
    • PIN
    • &REST

    Source

    No documentation provided.
  • EXTERNAL FUNCTION

    AVAILABLE-PINS

    Source

    Return a list of all available GPIO pins on the system.
    
    Note that the pins are not necessarily accessible;
    they may need to be exported first.

  • EXTERNAL FUNCTION

    BASE

    • CHIP
    • &REST

    Source

    Return the GPIO chip's base pin number.

  • EXTERNAL FUNCTION

    CHIP-FILE

    • CHIP
    • SUB
    • &REST

    Source

    Returns a file for the specified GPIO chip.
    
    See GPIO-FILE

  • EXTERNAL FUNCTION

    CHIP-PINS

    • CHIP
    • &REST

    Source

    Return a list of GPIO pin numbers on the chip.

  • EXTERNAL FUNCTION

    CHIPS

    Source

    Returns a list of known GPIO chips.

  • EXTERNAL FUNCTION

    DIRECTION

    • PIN
    • &REST

    Source

    Accessor to the GPIO pin's direction.
    
    The value should be either :IN or :OUT.

  • EXTERNAL FUNCTION

    (SETF DIRECTION)

    • VALUE
    • PIN
    • &REST

    Source

    No documentation provided.
  • EXTERNAL FUNCTION

    EDGE

    • PIN
    • &REST

    Source

    Accessor to the GPIO pin's interrupt edge.
    
    The value should be one of :NONE :RISING :FALLING :BOTH

  • EXTERNAL FUNCTION

    (SETF EDGE)

    • VALUE
    • PIN
    • &REST

    Source

    No documentation provided.
  • EXTERNAL FUNCTION

    EXPORT-PIN

    • &REST
    • PINS
    • &REST

    Source

    Export the specified pins so that they may be accessed from userspace.

  • EXTERNAL FUNCTION

    EXPORTED-PINS

    Source

    Returns a list of GPIO pins that are accessible.

  • EXTERNAL FUNCTION

    GPIO-FILE

    • SUB
    • &REST

    Source

    Returns an absolute path to the requested gpio file.
    
    See *GPIO-ROOT*

  • EXTERNAL FUNCTION

    LABEL

    • CHIP
    • &REST

    Source

    Return the GPIO chip's label.

  • EXTERNAL FUNCTION

    NGPIO

    • CHIP
    • &REST

    Source

    Return the number of GPIO pins on the chip.

  • EXTERNAL FUNCTION

    PIN-FILE

    • PIN
    • SUB
    • &REST

    Source

    Returns a file for the specified GPIO pin.
    
    See GPIO-FILE

  • EXTERNAL FUNCTION

    UNEXPORT-PIN

    • &REST
    • PINS
    • &REST

    Source

    Unexport the specified pins so that they can no longer be accessed from userspace.

  • EXTERNAL FUNCTION

    VALUE

    • PIN
    • &REST

    Source

    Accessor to the GPIO pin's value.
    
    When reading, the pin's direction should be :IN
    When setting, the pin's direction should be :OUT
    
    The value should be either NIL or T.

  • EXTERNAL FUNCTION

    (SETF VALUE)

    • VALUE
    • PIN
    • &REST

    Source

    No documentation provided.