Polish the docs for ReadTheDocs

Author: tannewt

README.md

@@ -0,0 +1,18 @@
+Adafruit CircuitPython BusDevice
+==============================
+
+.. image:: https://readthedocs.org/projects/adafruit-circuitpython-bus_device/badge/?version=latest
+    :target: https://circuitpython.readthedocs.io/projects/bus_device/en/latest/
+    :alt: Documentation Status
+
+The `I2CDevice` and `SPIDevice` helper classes make managing transaction state
+on a bus easy. For example, they manage locking the bus to prevent other
+concurrent access. For SPI devices, it manages the chip select and protocol
+changes such as mode. For I2C, it manages the device address.
+
+API
+---
+.. toctree::
+    :maxdepth: 3
+
+    adafruit_bus_device/index

README.rst

@@ -25,10 +25,12 @@ class I2CDevice:
     Represents a single I2C device and manages locking the bus and the device
     address.
 
-    :param I2C i2c: The I2C bus the device is on
+    :param ~nativeio.I2C i2c: The I2C bus the device is on
     :param int device_address: The 7 bit device address
 
-    Example::
+    Example:
+
+    .. code-block:: python
 
         import nativeio
         from board import *
@@ -44,6 +46,14 @@ class I2CDevice:
                 device.writeto(bytes_read)
     """
     def __init__(self, i2c, device_address):
+        # Verify that a deivce with that address exists.
+        while not i2c.try_lock():
+            pass
+        scan = i2c.scan()
+        i2c.unlock()
+        if device_address not in scan:
+            raise ValueError("No i2c device at address: " + str(hex(device_address)))
+
         self.i2c = i2c
         self.device_address = device_address
 
@@ -56,10 +66,10 @@ def readfrom_into(self, buf, **kwargs):
         as if ``buf[start:end]``. This will not cause an allocation like
         ``buf[start:end]`` will so it saves memory.
 
-             :param int address: 7-bit device address
-             :param bytearray buffer: buffer to write into
-             :param int start: Index to start writing at
-             :param int end: Index to write up to but not include
+        :param int address: 7-bit device address
+        :param bytearray buffer: buffer to write into
+        :param int start: Index to start writing at
+        :param int end: Index to write up to but not include
         """
         self.i2c.readfrom_into(self.device_address, buf, **kwargs)
 
@@ -72,11 +82,10 @@ def writeto(self, buf, **kwargs):
         as if ``buffer[start:end]``. This will not cause an allocation like
         ``buffer[start:end]`` will so it saves memory.
 
-          :param bytearray buffer: buffer containing the bytes to write
-          :param int start: Index to start writing from
-          :param int end: Index to read up to but not include
-          :param bool stop: If true, output an I2C stop condition after the
-                            buffer is written
+        :param bytearray buffer: buffer containing the bytes to write
+        :param int start: Index to start writing from
+        :param int end: Index to read up to but not include
+        :param bool stop: If true, output an I2C stop condition after the buffer is written
         """
         self.i2c.writeto(self.device_address, buf, **kwargs)
 

adafruit_bus_device/i2c_device.py

@@ -0,0 +1,14 @@
+Module Reference
+================
+
+`i2c_device` - A device on an i2c bus
++++++++++++++++++++++++++++++++++++++
+
+.. automodule:: adafruit_bus_device.i2c_device
+   :members:
+
+`spi_device` - A device on a SPI bus
+++++++++++++++++++++++++++++++++++++
+
+.. automodule:: adafruit_bus_device.spi_device
+    :members:

adafruit_bus_device/index.rst

@@ -25,23 +25,25 @@ class SPIDevice:
     Represents a single SPI device and manages locking the bus and the device
     address.
 
-    :param SPI spi: The SPI bus the device is on
+    :param ~nativeio.SPI spi: The SPI bus the device is on
     :param ~microcontroller.Pin chip_select: The chip select pin
 
-    Example::
+    Example:
+
+    .. code-block:: python
 
         import nativeio
         from board import *
         from adafruit_bus_device.spi_device import I2CDevice
 
-        with nativeio.SPI(SCK, MOSI, MISO) as spi:
-            device = SPIDevice(spi, D10)
+        with nativeio.SPI(SCK, MOSI, MISO) as spi_bus:
+            device = SPIDevice(spi_bus, D10)
             bytes_read = bytearray(4)
-            with device:
-                device.read(bytes_read)
+            with device as spi:
+                spi_device.read(bytes_read)
             # A second transaction
-            with device:
-                device.write(bytes_read)
+            with device as spi:
+                spi.write(bytes_read)
     """
     def __init__(self, spi, chip_select, baudrate=100000, polarity=0, phase=0):
         self.spi = spi