Raise erro rwhen attempting software I2C on platform without. Minimise imports on...

diff --git a/src/bitbangio.py b/src/bitbangio.py
index f21cb186c6f291ab15bf6a8b1c2a0714efaa1756..101bfff0412ba655275b12f3a7fd51a17d178a66 100644 (file)
--- a/src/bitbangio.py
+++ b/src/bitbangio.py
@@ -1,13 +1,15 @@
-from adafruit_blinka import Lockable
-from machine import I2C as _I2C
-from machine import Pin
+from adafruit_blinka import Lockable, agnostic
 
 
 class I2C(Lockable):
     def __init__(self, scl, sda, frequency=400000):
+        if agnostic.microcontroller == "stm32":
+            raise NotImplementedError("No software I2C on {}".format(agnostic.board))
         self.init(scl, sda, frequency)
 
     def init(self, scl, sda, frequency):
+        from machine import Pin
+        from machine import I2C as _I2C
         self.deinit()
         id = -1  # force bitbanging implementation - in future introspect platform if SDA/SCL matches hardware I2C
         self._i2c = _I2C(id, Pin(scl.id), Pin(sda.id), freq=frequency)
@@ -35,21 +37,24 @@ class I2C(Lockable):
         stop = True  # remove for efficiency later
         return self._i2c.readfrom_into(address, buffer, stop)
 
-    def writeto(self, address, buffer, start=0, end=None, stop=True, *a, **k):
+    def writeto(self, address, buffer, start=0, end=None, stop=True):
         if start is not 0 or end is not None:
             if end is None:
-                end = len(buffer)
-            buffer = memoryview(buffer)[start:end]
+                return self._i2c.writeto(address, memoryview(buffer)[start:], stop)
+            else:
+                return self._i2c.writeto(address, memoryview(buffer)[start:end], stop)
         return self._i2c.writeto(address, buffer, stop)
 
 
 # TODO untested, as actually busio.SPI was on tasklist https://github.com/adafruit/Adafruit_Micropython_Blinka/issues/2 :(
 class SPI(Lockable):
     def __init__(self, clock, MOSI=None, MISO=None):
+        from machine import SPI
         self._spi = SPI(-1)
-        self._pins = (clock.id, MOSI.id, MISO.id)
+        self._pins = (clock, MOSI, MISO)
 
     def configure(self, baudrate=100000, polarity=0, phase=0, bits=8):
+        from machine import SPI,Pin
         if self._locked:
             # TODO verify if _spi obj 'caches' sck, mosi, miso to avoid storing in _attributeIds (duplicated in busio)
             # i.e. #init ignores MOSI=None rather than unsetting
@@ -59,9 +64,9 @@ class SPI(Lockable):
                 phase=phase,
                 bits=bits,
                 firstbit=SPI.MSB,
-                sck=Pin(self._pins[0]),
-                mosi=Pin(self._pins[1]),
-                miso=Pin(self._pins[2]))
+                sck=Pin(self._pins[0].id),
+                mosi=Pin(self._pins[1].id),
+                miso=Pin(self._pins[2].id))
         else:
             raise RuntimeError("First call try_lock()")