Cl-Gpio

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)

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, it would be:

rpi23-pin-mapping

(Source)

Package Index

CL-GPIO (GPIO ORG.SHIRAKUMO.GPIO)

class

`PIN`

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

accessor (

`ACTIVE-LOW`

PIN)

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

accessor (

`DIRECTION`

PIN)

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

accessor (

`EDGE`

PIN)

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

accessor (

`VALUE`

PIN)

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

function (

`ALL-PINS`

)

Returns a list of PIN instances for all pins on the system.

See CL-GPIO-LLI:AVAILABLE-PINS
See ENSURE-PIN

function (

`AWAIT-VALUE`

PIN &OPTIONAL TIMEOUT)

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

function (

`CALL-WITH-PIN-HANDLER`

FUNCTION HANDLER PIN &OPTIONAL (EDGE NIL E-P) (ACTIVE-LOW NIL A-P))

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

function (

`CHIP`

PIN)

Returns the pin's chip device name.

See PIN-CHIP

function (

`ENSURE-PIN`

PIN &OPTIONAL REFRESH)

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

function (

`EXPORT`

&REST PINS)

Export the specified pins and return a list of according PIN instances.

See ENSURE-PIN
See CL-GPIO-LLI:EXPORT-PIN

function (

`NAME`

PIN)

Returns the pin's name or ID.

See PIN-NAME

function (

`PINS`

)

Returns a list of available/exported PIN instances.

See CL-GPIO-LLI:EXPORTED-PINS
See ENSURE-PIN

function (

`UNEXPORT`

&REST PINS)

Unexport the specified pins and invalidate their cache.

See *PIN-CACHE*
See CL-GPIO-LLI:UNEXPORT-PIN

macro (

`WITH-PIN-HANDLER`

(HANDLER PIN &OPTIONAL EDGE ACTIVE-LOW) &BODY BODY)

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)

special

`GPIO-ROOT`

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

accessor (

`ACTIVE-LOW`

PIN)

Accessor to whether the GPIO pin has an active low.

The value should be either NIL or T.

accessor (

`DIRECTION`

PIN)

Accessor to the GPIO pin's direction.

The value should be either :IN or :OUT.

accessor (

`EDGE`

PIN)

Accessor to the GPIO pin's interrupt edge.

The value should be one of :NONE :RISING :FALLING :BOTH

accessor (

`VALUE`

PIN)

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.

function (

`AVAILABLE-PINS`

)

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.

function (
BASE
CHIP)
```
Return the GPIO chip's base pin number.
```

function (

`CHIP-FILE`

CHIP SUB)

Returns a file for the specified GPIO chip.

See GPIO-FILE

function (

`CHIP-PINS`

CHIP)

Return a list of GPIO pin numbers on the chip.

function (
CHIPS
)
```
Returns a list of known GPIO chips.
```

function (

`EXPORT-PIN`

&REST PINS)

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

function (

`EXPORTED-PINS`

)

Returns a list of GPIO pins that are accessible.

function (

`GPIO-FILE`

SUB)

Returns an absolute path to the requested gpio file.

See *GPIO-ROOT*

function (
LABEL
CHIP)
```
Return the GPIO chip's label.
```

function (

`NGPIO`

CHIP)

Return the number of GPIO pins on the chip.

function (

`PIN-FILE`

PIN SUB)

Returns a file for the specified GPIO pin.

See GPIO-FILE

function (

`UNEXPORT-PIN`

&REST PINS)

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

cl-gpio

About cl-gpio

How To

Copyright

Package Index

CL-GPIO (GPIO ORG.SHIRAKUMO.GPIO)

`PIN`

`ACTIVE-LOW`

`DIRECTION`

`EDGE`

`VALUE`

`ALL-PINS`

`AWAIT-VALUE`

`CALL-WITH-PIN-HANDLER`

`CHIP`

`ENSURE-PIN`

`EXPORT`

`NAME`

`PINS`

`UNEXPORT`

`WITH-PIN-HANDLER`

CL-GPIO-LLI (ORG.SHIRAKUMO.GPIO.LLI)

`GPIO-ROOT`

`ACTIVE-LOW`

`DIRECTION`

`EDGE`

`VALUE`

`AVAILABLE-PINS`

`BASE`

`CHIP-FILE`

`CHIP-PINS`

`CHIPS`

`EXPORT-PIN`

`EXPORTED-PINS`

`GPIO-FILE`

`LABEL`

`NGPIO`

`PIN-FILE`

`UNEXPORT-PIN`