mcp4728: Add initial support for the mcp4728 i2c dac chip

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

klippy/extras/mcp4728.py

@@ -0,0 +1,23 @@
+# MCP4728 dac code
+#
+# Copyright (C) 2018  Kevin O'Connor <kevin@koconnor.net>
+#
+# This file may be distributed under the terms of the GNU GPLv3 license.
+import bus
+
+class mcp4728:
+    def __init__(self, config):
+        self.i2c = bus.MCU_I2C_from_config(config, default_addr=0)
+        scale = config.getfloat('scale', 1., above=0.)
+        # Configure registers
+        for i, name in enumerate('abcd'):
+            val = config.getfloat('channel_%s' % (name,), None,
+                                  minval=0., maxval=scale)
+            if val is not None:
+                self.set_dac(i, int(val * 4095. / scale + .5))
+    def set_dac(self, dac, value):
+        self.i2c.i2c_write([0x40 | (dac << 1),
+                            (value >> 8) & 0x0f, value & 0xff])
+
+def load_config_prefix(config):
+    return mcp4728(config)