"""
This module implements switching GPIOs via sysfs GPIO kernel interface.
Takes an integer property 'index' which refers to the already exported GPIO device.
Takes a boolean property 'invert' which inverts logical values if set to True (active-low)
"""
import logging
import os
[docs]
class GpioDigitalOutput:
_gpio_sysfs_path_prefix = '/sys/class/gpio'
@staticmethod
def _assert_gpio_line_is_exported(index):
gpio_sysfs_path = os.path.join(GpioDigitalOutput._gpio_sysfs_path_prefix,
f'gpio{index}')
# Deprecated: the exporter can export on acquire, we are leaving this
# in for now to support exporters which have not been updated yet.
if not os.path.exists(gpio_sysfs_path):
export_sysfs_path = os.path.join(GpioDigitalOutput._gpio_sysfs_path_prefix, 'export')
with open(export_sysfs_path, mode='wb') as export:
export.write(str(index).encode('utf-8'))
if not os.path.exists(gpio_sysfs_path):
raise ValueError("Device not found")
[docs]
def __init__(self, index, invert):
self.gpio_sysfs_value_fd = None
self._logger = logging.getLogger("Device: ")
GpioDigitalOutput._assert_gpio_line_is_exported(index)
gpio_sysfs_path = os.path.join(GpioDigitalOutput._gpio_sysfs_path_prefix,
f'gpio{index}')
gpio_sysfs_direction_path = os.path.join(gpio_sysfs_path, 'direction')
with open(gpio_sysfs_direction_path, 'rb') as direction_fd:
literal_value = direction_fd.read(3)
if literal_value != b"out":
self._logger.debug("Configuring GPIO %d as output.", index)
with open(gpio_sysfs_direction_path, 'wb') as direction_fd:
direction_fd.write(b'out')
gpio_sysfs_value_path = os.path.join(gpio_sysfs_path, 'value')
self.gpio_sysfs_value_fd = os.open(gpio_sysfs_value_path, flags=(os.O_RDWR | os.O_SYNC))
gpio_sysfs_active_low_path = os.path.join(gpio_sysfs_path, 'active_low')
with open(gpio_sysfs_active_low_path, 'w') as active_low_fd:
active_low_fd.write(str(int(invert)))
[docs]
def __del__(self):
if self.gpio_sysfs_value_fd:
os.close(self.gpio_sysfs_value_fd)
self.gpio_sysfs_value_fd = None
[docs]
def get(self):
os.lseek(self.gpio_sysfs_value_fd, 0, os.SEEK_SET)
literal_value = os.read(self.gpio_sysfs_value_fd, 1)
if literal_value == b'0':
return False
elif literal_value == b'1':
return True
raise ValueError("GPIO value is out of range.")
[docs]
def set(self, status):
self._logger.debug("Setting GPIO to `%s`.", status)
binary_value = None
if status is True:
binary_value = b'1'
elif status is False:
binary_value = b'0'
if binary_value is None:
raise ValueError("GPIO value is out of range.")
os.write(self.gpio_sysfs_value_fd, binary_value)
_gpios = {}
def _get_gpio_line(index, invert):
if index not in _gpios:
_gpios[index] = GpioDigitalOutput(index=index, invert=invert)
return _gpios[index]
[docs]
def handle_set(index, invert, status):
gpio_line = _get_gpio_line(index, invert)
gpio_line.set(status)
[docs]
def handle_get(index, invert):
gpio_line = _get_gpio_line(index, invert)
return gpio_line.get()
methods = {
'set': handle_set,
'get': handle_get,
}