sysfsdiomp.py

nio.py

##
# The MIT License (MIT)
#
# Copyright (c) 2014 Stefan Wendler
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
##

"""
Simple wrapper to libc open/read/write functions using FFI on
micropython.
"""

__author__ = 'Stefan Wendler, sw@kaltpost.de'

import ffi
import _libc

libc = _libc.get()

open = libc.func("i", "open", "si")
close = libc.func("i", "close", "i")
read = libc.func("i", "read", "isi")
write = libc.func("i", "write", "isi")
lseek = libc.func("i", "lseek", "iii")

'''
Open Flags
'''
O_ACCMODE = 3
O_RDONLY = 0 
O_WRONLY = 1 
O_RDWR = 2 
O_CREAT = 100
O_EXCL = 200
O_NOCTTY = 400 
O_TRUNC = 1000 
O_APPEND = 2000 
O_NONBLOCK = 4000  
O_NDELAY = O_NONBLOCK
O_SYNC = 4010000  
O_FSYNC = O_SYNC 
O_ASYNC = 20000    

'''
Some common error codes
'''
EPERM = 1		# Operation not permitted
ENOENT = 2  		# No such file or directory
EIO = 5			# I/O error
EAGAIN = 11		# Try again 
ENOMEM = 12		# Out of memory
EACCES = 13		# Permission denied
EEXIST = 17		# File exists
EISDIR = 21		# Is a directory
EMFILE = 24		# Too many open files
ETXTBSY = 26		# Text file busy
EFBIG = 27		# File too large
ENOSPC = 28		# No space left on device
EROFS= 30		# Read-only file system

'''
Seek values
'''
SEEK_SET = 0
SEEK_CUR = 1
SEEK_END = 2


def bytebuffer(size):
	'''
	Create a bytebuffer of given size (e.g. for use with read)
	'''
	return ('\0' * size)

sysfsdiomp.py

##
# The MIT License (MIT)
#
# Copyright (c) 2014 Stefan Wendler
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
##

"""
Digital IO on VoCode Board using SYSFS

This is the version which runs with micropython
by using FFI to directely call libc open/read/write
functions.  
"""

__author__ = 'Stefan Wendler, sw@kaltpost.de'

import nio

# Available pins on th VoCore
GPIO0 = 0
GPIO7 = 7
GPIO8 = 8
GPIO9 = 9
GPIO12 = 12
GPIO13 = 13
GPIO14 = 14
GPIO17 = 17
GPIO18 = 18
GPIO19 = 19
GPIO20 = 20
GPIO21 = 21
GPIO22 = 22
GPIO23 = 23
GPIO24 = 24
GPIO25 = 25
GPIO26 = 26


class Pin:

    pinId = None
    pinDir = ""
    stateBuf = "\0"

    def __init__(self, pinId):
        self.pinId = pinId
        self.export()

    def __del__(self):
        self.unexport()

    def state(self):
        f = nio.open(self.pinDir + "value", nio.O_RDONLY)
	nio.read(f, self.stateBuf, 1)
        nio.close(f)

        if self.stateBuf[0] == "1":
            return 1

        return 0

    def export(self):
        f = nio.open("/sys/class/gpio/export", nio.O_WRONLY)
	s = "%d" % self.pinId
        nio.write(f, s, len(s))
        nio.close(f)
        self.pinDir = "/sys/class/gpio/gpio%d/" % self.pinId

    def unexport(self):
        f = nio.open("/sys/class/gpio/unexport", nio.O_WRONLY)
	s = "%d" % self.pinId
        nio.write(f, s, len(s))
        nio.close(f)

    def __str__(self):
        return ("P_%d" % self.pinId)


class PinIn(Pin):

    def __init__(self, pinId):
        Pin.__init__(self, pinId)
        f = nio.open(self.pinDir + "direction", nio.O_WRONLY)
	s = "in"
        nio.write(f, s, len(s))
        nio.close(f)


class PinOut(Pin):

    def __init__(self, pinId):
        Pin.__init__(self, pinId)
        f = nio.open(self.pinDir + "direction", nio.O_WRONLY)
	s = "out"
        nio.write(f, s, len(s))
        nio.close(f)

    def set(self):
        f = nio.open(self.pinDir + "value", nio.O_WRONLY)
	s = "1"
        nio.write(f, s, len(s))
        nio.close(f)

    def clear(self):
        f = nio.open(self.pinDir + "value", nio.O_WRONLY)
	s = "0"
        nio.write(f, s, len(s))
        nio.close(f)

    def toggle(self):
        if self.state() == 1:
            self.clear()
        else:
            self.set()


class DigitalIO:

    def __init__(self):
        pass

    @staticmethod
    def get_input(self, pinId):
        return PinIn(pinId)

    @staticmethod
    def get_output(pinId):
        return PinOut(pinId)

    @staticmethod
    def release(self, pin):
        del pin


def main():

    import time

    pin = DigitalIO.get_output(GPIO12)

    while True:
        pin.toggle()
        time.sleep(0.25)


if __name__ == "__main__":
    main()

Simple Python program to drive GPIOs on the VoCore/MIPS using sysfs and micropython.

Note: I was not able to get micropython read/write the GPIO sysfs entries on the MIPS with Kernel 3.14 with it's build in open/read/write methods. Thus, I used FFI to wrap the libc's open/read/write methods to micropython which works.

My micropython install throws an ImportError: no module named '_libc'

If I do libc = ffi.open("libc.so.0") it seems to work. I found this line here: https://github.com/micropython/micropython/blob/master/examples/unix/ffi_example.py

Am I missing something? My micropython is "Micro Python on 2015-02-23; linux version" from opkg on the VoCore.