RPi.GPIO是通过Python/C API实现的，C代码操作底层寄存器， python通过Python/C API调用这些C接口。
这是关于RPi.GPIO项目的介绍。 其中提到了有python 垃圾回收机制，并不适合于实时要求的应用。
https://pypi.org/project/RPi.GPIO/
关于Python/C API，有点类似于JNI，PyObject 作为common object,用于参数和return
https://docs.python.org/3/c-api/intro.html
https://docs.python.org/3/c-api/structures.html#c.PyObjectPython
在树莓派中之前编译的系统，python, 以及RPi.GPIO module都已经预装了，
pi@raspberrypi:~/python $ python led.py 执行python led.py脚本，LED闪烁。
#!/usr/bin/python
# -*- coding:utf-8 -*-
import RPi.GPIO as GPIO
import time
LED = 26
GPIO.setmode(GPIO.BCM)
GPIO.setup(LED,GPIO.OUT)
try:
while True:
GPIO.output(LED,GPIO.HIGH)
time.sleep(1)
GPIO.output(LED,GPIO.LOW)
time.sleep(1)
except:
print("except")
GPIO.cleanup()下面是RPi.GPIO中 setmode的C代码
// python function setmode(mode)
static PyObject *py_setmode(PyObject *self, PyObject *args)
{
int new_mode;
if (!PyArg_ParseTuple(args, "i", &new_mode))
return NULL;
if (gpio_mode != MODE_UNKNOWN && new_mode != gpio_mode)
{
PyErr_SetString(PyExc_ValueError, "A different mode has already been set!");
return NULL;
}
if (setup_error)
{
PyErr_SetString(PyExc_RuntimeError, "Module not imported correctly!");
return NULL;
}
if (new_mode != BOARD && new_mode != BCM)
{
PyErr_SetString(PyExc_ValueError, "An invalid mode was passed to setmode()");
return NULL;
}
if (rpiinfo.p1_revision == 0 && new_mode == BOARD)
{
PyErr_SetString(PyExc_RuntimeError, "BOARD numbering system not applicable on compute module");
return NULL;
}
gpio_mode = new_mode;
Py_RETURN_NONE;
}PyMethodDef rpi_gpio_methods[] = {
{"setup", (PyCFunction)py_setup_channel, METH_VARARGS | METH_KEYWORDS, "Set up a GPIO channel or list of channels with a direction and (optional) pull/up down control\nchannel - either board pin number or BCM number depending on which mode is set.\ndirection - IN or OUT\n[pull_up_down] - PUD_OFF (default), PUD_UP or PUD_DOWN\n[initial] - Initial value for an output channel"},
{"cleanup", (PyCFunction)py_cleanup, METH_VARARGS | METH_KEYWORDS, "Clean up by resetting all GPIO channels that have been used by this program to INPUT with no pullup/pulldown and no event detection\n[channel] - individual channel or list/tuple of channels to clean up. Default - clean every channel that has been used."},
{"output", py_output_gpio, METH_VARARGS, "Output to a GPIO channel or list of channels\nchannel - either board pin number or BCM number depending on which mode is set.\nvalue - 0/1 or False/True or LOW/HIGH"},
{"input", py_input_gpio, METH_VARARGS, "Input from a GPIO channel. Returns HIGH=1=True or LOW=0=False\nchannel - either board pin number or BCM number depending on which mode is set."},
{"setmode", py_setmode, METH_VARARGS, "Set up numbering mode to use for channels.\nBOARD - Use Raspberry Pi board numbers\nBCM - Use Broadcom GPIO 00..nn numbers"},
{"getmode", py_getmode, METH_VARARGS, "Get numbering mode used for channel numbers.\nReturns BOARD, BCM or None"},
{"add_event_detect", (PyCFunction)py_add_event_detect, METH_VARARGS | METH_KEYWORDS, "Enable edge detection events for a particular GPIO channel.\nchannel - either board pin number or BCM number depending on which mode is set.\nedge - RISING, FALLING or BOTH\n[callback] - A callback function for the event (optional)\n[bouncetime] - Switch bounce timeout in ms for callback"},
{"remove_event_detect", py_remove_event_detect, METH_VARARGS, "Remove edge detection for a particular GPIO channel\nchannel - either board pin number or BCM number depending on which mode is set."},
{"event_detected", py_event_detected, METH_VARARGS, "Returns True if an edge has occured on a given GPIO. You need to enable edge detection using add_event_detect() first.\nchannel - either board pin number or BCM number depending on which mode is set."},
{"add_event_callback", (PyCFunction)py_add_event_callback, METH_VARARGS | METH_KEYWORDS, "Add a callback for an event already defined using add_event_detect()\nchannel - either board pin number or BCM number depending on which mode is set.\ncallback - a callback function"},
{"wait_for_edge", (PyCFunction)py_wait_for_edge, METH_VARARGS | METH_KEYWORDS, "Wait for an edge. Returns the channel number or None on timeout.\nchannel - either board pin number or BCM number depending on which mode is set.\nedge - RISING, FALLING or BOTH\n[bouncetime] - time allowed between calls to allow for switchbounce\n[timeout] - timeout in ms"},
{"gpio_function", py_gpio_function, METH_VARARGS, "Return the current GPIO function (IN, OUT, PWM, SERIAL, I2C, SPI)\nchannel - either board pin number or BCM number depending on which mode is set."},
{"setwarnings", py_setwarnings, METH_VARARGS, "Enable or disable warning messages"},
{NULL, NULL, 0, NULL}
};