import os
import fcntl
import struct
import time
import atexit
import threading
ADS111x_ADDRESS = 0x48
I2C_SLAVE = 0x0703
class __I2CDev(object):
def __init__(self):
self._os_close = os.close
# Initialize i2c interface and register it for closing on exit.
self._dev = os.open("/dev/i2c-1", os.O_SYNC | os.O_RDWR)
if self._dev < 0:
raise ImportError("i2c device not found")
else:
if fcntl.ioctl(self._dev, I2C_SLAVE, ADS111x_ADDRESS) < 0:
self._close()
raise ImportError("Failed to set up i2c address")
else:
atexit.register(self._close)
def _close(self):
self._os_close(self._dev)
def write(self, data):
os.write(self._dev, data)
def read(self, n):
return os.read(self._dev, n)
i2c = __I2CDev()
# mutex for multi threading requests
lock = threading.Lock()
def measure(channel):
"""
Measure voltage on chip input.
Raises OSError(Errno 121) "Remote I/O error" on reading error.
Thread safe.
:param channel: chip channel to use.
:return: Voltage in Volts.
"""
global i2c
if channel < 0 or channel > 3:
raise ValueError("Wrong channel")
lock.acquire()
# configure
data = struct.pack(">BH",
0x01, # config register
# single shot mode, +-4.096V, AINN = GND
((0b100 | channel) << 12) | 0x8380
)
i2c.write(data)
# wait for conversion
while True:
i2c.write(struct.pack("B", 0x01))
if struct.unpack(">H", i2c.read(2))[0] & 0x8000 != 0:
break
time.sleep(0.0001)
# read result
i2c.write(struct.pack("B", 0x00)) # conversion register
v = struct.unpack(">h", i2c.read(2))[0]
lock.release()
return v / 8000.0 # / 32768.0 * 4.096 according to specified range
# check if ads111x is connected
try:
measure(0)
except OSError:
raise ImportError("ads111x is not connected")
# for test purpose
if __name__ == "__main__":
while True:
for i in range(0, 4):
print(str(i), measure(i))
print("-----------------------------")
time.sleep(0.5)
