Add I2C General Call Commands

This Commit,
- Adds _general_call static methods for executing different general calls to MCP4728
- Adds reset, wakeup and soft_update general call static methods

Author: codenio

adafruit_mcp4728.py

@@ -36,6 +36,14 @@
 
 _MCP4728_CH_A_MULTI_EEPROM = 0x50
 
+_MCP4728_GENERAL_CALL_ADDRESS = 0x00
+
+_MCP4728_GENERAL_CALL_RESET_COMMAND = 0x06
+
+_MCP4728_GENERAL_CALL_WAKEUP_COMMAND = 0x09
+
+_MCP4728_GENERAL_CALL_SOFTWARE_UPDATE_COMMAND = 0x08
+
 
 class CV:
     """struct helper"""
@@ -227,6 +235,35 @@ def _chunk(big_list, chunk_size):
         for i in range(0, len(big_list), chunk_size):
             yield big_list[i : i + chunk_size]
 
+    def _general_call(self, byte_command):
+        buffer_list = [_MCP4728_GENERAL_CALL_ADDRESS]
+        buffer_list += [byte_command]
+
+        buf = bytearray(buffer_list)
+
+        with self.i2c_device as i2c:
+            i2c.write(buf)
+
+    def reset(self):
+        """Internal Reset similar to a Power-on Reset (POR).
+        The contents of the EEPROM are loaded into each DAC input
+        and output registers immediately"""
+
+        self._general_call(_MCP4728_GENERAL_CALL_RESET_COMMAND)
+
+    def wakeup(self):
+        """Reset the Power-Down bits (PD1, PD0 = 0,0) and
+        Resumes Normal Operation mode"""
+
+        self._general_call(_MCP4728_GENERAL_CALL_WAKEUP_COMMAND)
+
+    def soft_update(self):
+        """Updates all DAC analog outputs (VOUT) at the same time."""
+
+        self._general_call(_MCP4728_GENERAL_CALL_SOFTWARE_UPDATE_COMMAND)
+
+    # TODO : general_call read address
+
 
 class Channel:
     """An instance of a single channel for a multi-channel DAC.

examples/mcp4728_generalcalltest.py

@@ -0,0 +1,22 @@
+# SPDX-FileCopyrightText: 2021 ladyada for Adafruit Industries
+# SPDX-License-Identifier: MIT
+
+import board
+import adafruit_mcp4728
+
+i2c = board.I2C()  # uses board.SCL and board.SDA
+mcp4728 = adafruit_mcp4728.MCP4728(i2c)
+
+mcp4728.channel_a.value = 65535  # Voltage = VDD
+mcp4728.channel_b.value = int(65535 / 2)  # VDD/2
+mcp4728.channel_c.value = int(65535 / 4)  # VDD/4
+mcp4728.channel_d.value = 0  # 0V
+
+mcp4728.save_settings()  # save current voltages into EEPROM
+
+mcp4728.channel_a.value = 0  # Modify output
+mcp4728.channel_b.value = 0  # Modify output
+mcp4728.channel_c.value = 0  # Modify output
+mcp4728.channel_d.value = 65535  # Modify output
+
+mcp4728.reset()  # reset MCP4728