adafruit_bus_device/i2c_device.py

@@ -62,6 +62,7 @@ class I2CDevice:
     def __init__(self, i2c, device_address, probe=True):
 
         self.i2c = i2c
+        self._has_write_read = hasattr(self.i2c, "writeto_then_readfrom")
         self.device_address = device_address
 
         if probe:
@@ -84,10 +85,10 @@ class I2CDevice:
             end = len(buf)
         self.i2c.readfrom_into(self.device_address, buf, start=start, end=end)
 
-    def write(self, buf, *, start=0, end=None):
+    def write(self, buf, *, start=0, end=None, stop=True):
         """
-        Write the bytes from ``buffer`` to the device, then transmit a stop
+        Write the bytes from ``buffer`` to the device. Transmits a stop bit if
-        bit.
+        ``stop`` is set.
 
         If ``start`` or ``end`` is provided, then the buffer will be sliced
         as if ``buffer[start:end]``. This will not cause an allocation like
@@ -96,10 +97,11 @@ class I2CDevice:
         :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; if None, use ``len(buf)``
+        :param bool stop: If true, output an I2C stop condition after the buffer is written
         """
         if end is None:
             end = len(buf)
-        self.i2c.writeto(self.device_address, buf, start=start, end=end)
+        self.i2c.writeto(self.device_address, buf, start=start, end=end, stop=stop)
 
     # pylint: disable-msg=too-many-arguments
     def write_then_readinto(
@@ -111,6 +113,7 @@ class I2CDevice:
         out_end=None,
         in_start=0,
         in_end=None,
+        stop=False
     ):
         """
         Write the bytes from ``out_buffer`` to the device, then immediately
@@ -133,12 +136,16 @@ class I2CDevice:
         :param int out_end: Index to read up to but not include; if None, use ``len(out_buffer)``
         :param int in_start: Index to start writing at
         :param int in_end: Index to write up to but not include; if None, use ``len(in_buffer)``
+        :param bool stop: Deprecated
         """
         if out_end is None:
             out_end = len(out_buffer)
         if in_end is None:
             in_end = len(in_buffer)
-
+        if stop:
+            raise ValueError("Stop must be False. Use writeto instead.")
+        if self._has_write_read:
+            # In linux, at least, this is a special kernel function call
             self.i2c.writeto_then_readfrom(
                 self.device_address,
                 out_buffer,
@@ -149,6 +156,11 @@ class I2CDevice:
                 in_end=in_end,
             )
 
+        else:
+            # If we don't have a special implementation, we can fake it with two calls
+            self.write(out_buffer, start=out_start, end=out_end, stop=False)
+            self.readinto(in_buffer, start=in_start, end=in_end)
+
     # pylint: enable-msg=too-many-arguments
 
     def __enter__(self):