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Gets the base of XIOs on C.H.I.P. computers. Currently on 4.3, it's 408, and on 4.4 it's 1016. This calculates it dynamically
import os
GPIO_PATH = "/sys/class/gpio" # The root of the GPIO directories
EXPANDER = "pcf8574a" # This is the expander that is used on CHIP for the XIOs
def get_xio_base():
'''
Determines the base of the XIOs on the system by iterating through the /sys/class/gpio
directory and looking for the expander that is used. It then looks for the
"base" file and returns its contents as an integer
'''
names = os.listdir(GPIO_PATH)
for name in names: # loop through child directories
prefix = GPIO_PATH + "/" + name + "/"
file_name = prefix + "label"
if os.path.isfile(file_name): # is there a label file in the directory?
with open(file_name) as label:
contents = label.read()
if contents.startswith(EXPANDER): # does label contain our expander?
file_name = prefix + "base"
with open(file_name) as base: # read the sibling file named base
contents = base.read()
return int(contents) # convert result to an int
if __name__ == '__main__':
print get_xio_base()
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