ads111x driver

cnc/sensors/ads111x.py

@@ -0,0 +1,70 @@
+import os
+import fcntl
+import struct
+import time
+import atexit
+
+ADS111x_ADDRESS = 0x48
+I2C_SLAVE = 0x0703
+
+# Initialize i2c interface and register it for closing on exit.
+__i2c_dev = os.open("/dev/i2c-1", os.O_SYNC | os.O_RDWR)
+
+
+def __close():
+    os.close(__i2c_dev)
+
+if __i2c_dev < 0:
+    raise ImportError("i2c device not found")
+else:
+    if fcntl.ioctl(__i2c_dev, I2C_SLAVE, ADS111x_ADDRESS) < 0:
+        __close()
+        raise ImportError("Failed to set up i2c address")
+    else:
+        atexit.register(__close)
+
+
+def measure(channel):
+    """
+    Measure voltage on chip input.
+    :param channel: chip channel to use.
+    :return: Voltage in Volts, None if no device connected.
+    """
+    global __i2c_dev
+    if channel < 0 or channel > 3:
+        raise ValueError("Wrong channel")
+    if __i2c_dev < 0:
+        return None
+    # configure
+    data = struct.pack(">BH",
+                       0x01,  # config register
+                       # single shot mode, +-4.096V, AINN = GND
+                       ((0b100 | channel) << 12) | 0x8380
+                       )
+    os.write(__i2c_dev, data)
+    # wait for conversion
+    while True:
+        os.write(__i2c_dev, struct.pack("B", 0x01))
+        if struct.unpack(">H", os.read(__i2c_dev, 2))[0] & 0x8000 != 0:
+            break
+        time.sleep(0.0001)
+    # read result
+    os.write(__i2c_dev, struct.pack("B", 0x00))  # conversion register
+    v = struct.unpack(">h", os.read(__i2c_dev, 2))[0]
+    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)