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Thank you for the answer. I want to adapt this raspberrypi script to my Pycom WiPy. but I stuck ... :-(
#!/usr/bin/python
import io # used to create file streams
import fcntl # used to access I2C parameters like addresses
import time # used for sleep delay and timestamps
import string # helps parse strings
class AtlasI2C:
long_timeout = 1.5 # the timeout needed to query readings and calibrations
short_timeout = .5 # timeout for regular commands
default_bus = 1 # the default bus for I2C on the newer Raspberry Pis, certain older boards use bus 0
default_address = 98 # the default address for the sensor
current_addr = default_address
def __init__(self, address=default_address, bus=default_bus):
# open two file streams, one for reading and one for writing
# the specific I2C channel is selected with bus
# it is usually 1, except for older revisions where its 0
# wb and rb indicate binary read and write
self.file_read = io.open("/dev/i2c-"+str(bus), "rb", buffering=0)
self.file_write = io.open("/dev/i2c-"+str(bus), "wb", buffering=0)
# initializes I2C to either a user specified or default address
self.set_i2c_address(address)
def set_i2c_address(self, addr):
# set the I2C communications to the slave specified by the address
# The commands for I2C dev using the ioctl functions are specified in
# the i2c-dev.h file from i2c-tools
I2C_SLAVE = 0x703
fcntl.ioctl(self.file_read, I2C_SLAVE, addr)
fcntl.ioctl(self.file_write, I2C_SLAVE, addr)
self.current_addr = addr
def write(self, cmd):
# appends the null character and sends the string over I2C
cmd += "\00"
self.file_write.write(cmd)
def read(self, num_of_bytes=31):
# reads a specified number of bytes from I2C, then parses and displays the result
res = self.file_read.read(num_of_bytes) # read from the board
response = filter(lambda x: x != '\x00', res) # remove the null characters to get the response
if ord(response[0]) == 1: # if the response isn't an error
# change MSB to 0 for all received characters except the first and get a list of characters
char_list = map(lambda x: chr(ord(x) & ~0x80), list(response[1:]))
# NOTE: having to change the MSB to 0 is a glitch in the raspberry pi, and you shouldn't have to do this!
return "Command succeeded " + ''.join(char_list) # convert the char list to a string and returns it
else:
return "Error " + str(ord(response[0]))
def query(self, string):
# write a command to the board, wait the correct timeout, and read the response
self.write(string)
# the read and calibration commands require a longer timeout
if((string.upper().startswith("R")) or
(string.upper().startswith("CAL"))):
time.sleep(self.long_timeout)
elif string.upper().startswith("SLEEP"):
return "sleep mode"
else:
time.sleep(self.short_timeout)
return self.read()
def close(self):
self.file_read.close()
self.file_write.close()
def list_i2c_devices(self):
prev_addr = self.current_addr # save the current address so we can restore it after
i2c_devices = []
for i in range (0,128):
try:
self.set_i2c_address(i)
self.read()
i2c_devices.append(i)
except IOError:
pass
self.set_i2c_address(prev_addr) # restore the address we were using
return i2c_devices
def main():
device = AtlasI2C() # creates the I2C port object, specify the address or bus if necessary
print(">> Atlas Scientific sample code")
print(">> Any commands entered are passed to the board via I2C except:")
print(">> List_addr lists the available I2C addresses.")
print(">> Address,xx changes the I2C address the Raspberry Pi communicates with.")
print(">> Poll,xx.x command continuously polls the board every xx.x seconds")
print(" where xx.x is longer than the %0.2f second timeout." % AtlasI2C.long_timeout)
print(">> Pressing ctrl-c will stop the polling")
# main loop
while True:
input = raw_input("Enter command: ")
if input.upper().startswith("LIST_ADDR"):
devices = device.list_i2c_devices()
for i in range(len (devices)):
print devices[i]
# address command lets you change which address the Raspberry Pi will poll
elif input.upper().startswith("ADDRESS"):
addr = int(string.split(input, ',')[1])
device.set_i2c_address(addr)
print("I2C address set to " + str(addr))
# continuous polling command automatically polls the board
elif input.upper().startswith("POLL"):
delaytime = float(string.split(input, ',')[1])
# check for polling time being too short, change it to the minimum timeout if too short
if delaytime < AtlasI2C.long_timeout:
print("Polling time is shorter than timeout, setting polling time to %0.2f" % AtlasI2C.long_timeout)
delaytime = AtlasI2C.long_timeout
# get the information of the board you're polling
info = string.split(device.query("I"), ",")[1]
print("Polling %s sensor every %0.2f seconds, press ctrl-c to stop polling" % (info, delaytime))
try:
while True:
print(device.query("R"))
time.sleep(delaytime - AtlasI2C.long_timeout)
except KeyboardInterrupt: # catches the ctrl-c command, which breaks the loop above
print("Continuous polling stopped")
# if not a special keyword, pass commands straight to board
else:
if len(input) == 0:
print "Please input valid command."
else:
try:
print(device.query(input))
except IOError:
print("Query failed \n - Address may be invalid, use List_addr command to see available addresses")
if __name__ == '__main__':
main()
