working code & example

Author: ladyada

README.md

@@ -13,7 +13,7 @@ Introduction
     :target: https://travis-ci.org/adafruit/Adafruit_CircuitPython_MPRLS
     :alt: Build Status
 
-.. todo:: Describe what the library does.
+CircuitPython library to support VEML6075 UVA & UVB sensor.
 
 Dependencies
 =============
@@ -29,6 +29,22 @@ This is easily achieved by downloading
 Usage Example
 =============
 
+.. code-block:: python
+	import time
+	import board
+	import busio
+	import adafruit_mprls
+
+	i2c = busio.I2C(board.SCL, board.SDA)
+
+	# Simplest use, connect to default over I2C
+	mpr = adafruit_mprls.MPRLS(i2c, psi_min=0, psi_max=25)
+
+
+	while True:
+	    print((mpr.pressure,))
+	    time.sleep(1)
+
 .. todo:: Add a quick, simple example. It and other examples should live in the examples folder and be included in docs/examples.rst.
 
 Contributing

README.rst

@@ -45,3 +45,90 @@
 
 __version__ = "0.0.0-auto.0"
 __repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_MPRLS.git"
+
+
+import time
+from adafruit_bus_device.i2c_device import I2CDevice
+from digitalio import Direction
+from micropython import const
+
+# pylint: disable=bad-whitespace
+_MPRLS_DEFAULT_ADDR = const(0x18)
+# pylint: enable=bad-whitespace
+
+class MPRLS:
+    """
+    Driver base for the MPRLS pressure sensor
+    :param i2c_bus: The `busio.I2C` object to use. This is the only required parameter.
+    :param int addr: The optional I2C address, defaults to 0x18
+    :param microcontroller.Pin reset_pin: Optional digitalio pin for hardware resetting
+    :param microcontroller.Pin eoc_pin: Optional digitalio pin for getting End Of Conversion signal
+    :param float psi_min: The minimum pressure in PSI, defaults to 0
+    :param float psi_max: The maximum pressure in PSI, defaults to 25
+    """
+    
+    def __init__(self, i2c_bus, *, addr = _MPRLS_DEFAULT_ADDR,
+                 reset_pin = None, eoc_pin = None, psi_min = 0, psi_max = 25):
+        # Init I2C
+        self._i2c = I2CDevice(i2c_bus, addr)
+        self._buffer = bytearray(4)
+
+        # Optional hardware reset pin
+        if reset_pin is not None:
+            reset_pin.direction = Direction.OUTPUT
+            reset_pin.value = True
+            reset_pin.value = False
+            time.sleep(0.01)
+            reset_pin.value = True
+        time.sleep(0.005) # Start up timing
+
+        # Optional end-of-conversion pin
+        self._eoc = eoc_pin
+        if eoc_pin is not None:
+            self._eoc.direction = Direction.INPUT
+
+        self._psimax = psi_max
+        self._psimin = psi_min
+        # That's pretty much it, there's no ID register :(
+
+    @property
+    def pressure(self):
+        """The measured pressure, in hPa"""
+        return self._read_data()
+
+
+    def _read_data(self):
+        """Read the status & 24-bit data reading"""
+        self._buffer[0] = 0xAA
+        self._buffer[1] = 0
+        self._buffer[2] = 0
+        with self._i2c as i2c:
+            # send command
+            i2c.write(self._buffer, end=3)
+            # ready busy flag/status
+            while True:
+                # check End of Convert pin first, if we can
+                if self._eoc is not None:
+                    if self._eoc.value:
+                        break
+                # or you can read the status byte
+                i2c.readinto(self._buffer, end=1)
+                if not self._buffer[0] & 0x20:
+                    break
+            # no longer busy!
+            i2c.readinto(self._buffer, end=4)
+
+        # check other status bits
+        if self._buffer[0] & 0x01:
+            raise RuntimeError("Internal math saturation")
+        if self._buffer[0] & 0x04:
+            raise RuntimeError("Integrity failure")
+        
+        # All is good, calculate the PSI and convert to hPA
+        raw_psi = (self._buffer[1] << 16) | (self._buffer[2] << 8) | self._buffer[3]
+        # use the 10-90 calibration curve
+        psi = (raw_psi - 0x19999A) * (self._psimax-self._psimin)
+        psi /= 0xE66666 - 0x19999A
+        psi += self._psimin
+        # convert PSI to hPA
+        return psi * 68.947572932

adafruit_mprls.py

@@ -0,0 +1,22 @@
+import time
+import board
+import busio
+import adafruit_mprls
+
+i2c = busio.I2C(board.SCL, board.SDA)
+
+# Simplest use, connect to default over I2C
+mpr = adafruit_mprls.MPRLS(i2c, psi_min=0, psi_max=25)
+
+# You can also specify both reset and eoc pins
+"""
+import digitalio
+reset = digitalio.DigitalInOut(board.D5)
+eoc = digitalio.DigitalInOut(board.D6)
+mpr = adafruit_mprls.MPRLS(i2c, eoc_pin=eoc, reset_pin=reset,
+                           psi_min=0, psi_max=25) 
+"""
+
+while True:
+    print((mpr.pressure,))
+    time.sleep(1)