PiClock project

ht16k33/ht16k33.py

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+class HT16K33:
+    """
+    A simple, generic driver for the I2C-connected Holtek HT16K33 controller chip.
+    This release supports MicroPython and CircuitPython
+
+    Bus:        I2C
+    Author:     Tony Smith (@smittytone)
+    License:    MIT
+    Copyright:  2023
+    """
+
+    # *********** CONSTANTS **********
+
+    HT16K33_GENERIC_DISPLAY_ON = 0x81
+    HT16K33_GENERIC_DISPLAY_OFF = 0x80
+    HT16K33_GENERIC_SYSTEM_ON = 0x21
+    HT16K33_GENERIC_SYSTEM_OFF = 0x20
+    HT16K33_GENERIC_DISPLAY_ADDRESS = 0x00
+    HT16K33_GENERIC_CMD_BRIGHTNESS = 0xE0
+    HT16K33_GENERIC_CMD_BLINK = 0x81
+
+    # *********** PRIVATE PROPERTIES **********
+
+    i2c = None
+    address = 0
+    brightness = 15
+    flash_rate = 0
+
+    # *********** CONSTRUCTOR **********
+
+    def __init__(self, i2c, i2c_address):
+        assert 0x00 <= i2c_address < 0x80, "ERROR - Invalid I2C address in HT16K33()"
+        self.i2c = i2c
+        self.address = i2c_address
+        self.power_on()
+
+    # *********** PUBLIC METHODS **********
+
+    def set_blink_rate(self, rate=0):
+        """
+        Set the display's flash rate.
+
+        Only four values (in Hz) are permitted: 0, 2, 1, and 0,5.
+
+        Args:
+            rate (int): The chosen flash rate. Default: 0Hz (no flash).
+        """
+        assert rate in (0, 0.5, 1, 2), "ERROR - Invalid blink rate set in set_blink_rate()"
+        self.blink_rate = rate & 0x03
+        self._write_cmd(self.HT16K33_GENERIC_CMD_BLINK | rate << 1)
+
+    def set_brightness(self, brightness=15):
+        """
+        Set the display's brightness (ie. duty cycle).
+
+        Brightness values range from 0 (dim, but not off) to 15 (max. brightness).
+
+        Args:
+            brightness (int): The chosen flash rate. Default: 15 (100%).
+        """
+        if brightness < 0 or brightness > 15: brightness = 15
+        self.brightness = brightness
+        self._write_cmd(self.HT16K33_GENERIC_CMD_BRIGHTNESS | brightness)
+
+    def draw(self):
+        """
+        Writes the current display buffer to the display itself.
+
+        Call this method after updating the buffer to update
+        the LED itself.
+        """
+        self._render()
+
+    def update(self):
+        """
+        Alternative for draw() for backwards compatibility
+        """
+        self._render()
+
+    def clear(self):
+        """
+        Clear the buffer.
+
+        Returns:
+            The instance (self)
+        """
+        for i in range(0, len(self.buffer)): self.buffer[i] = 0x00
+        return self
+
+    def power_on(self):
+        """
+        Power on the controller and display.
+        """
+        self._write_cmd(self.HT16K33_GENERIC_SYSTEM_ON)
+        self._write_cmd(self.HT16K33_GENERIC_DISPLAY_ON)
+
+    def power_off(self):
+        """
+        Power on the controller and display.
+        """
+        self._write_cmd(self.HT16K33_GENERIC_DISPLAY_OFF)
+        self._write_cmd(self.HT16K33_GENERIC_SYSTEM_OFF)
+
+    # ********** PRIVATE METHODS **********
+
+    def _render(self):
+        """
+        Write the display buffer out to I2C
+        """
+        buffer = bytearray(len(self.buffer) + 1)
+        buffer[1:] = self.buffer
+        buffer[0] = 0x00
+        self.i2c.writeto(self.address, bytes(buffer))
+
+    def _write_cmd(self, byte):
+        """
+        Writes a single command to the HT16K33. A private method.
+        """
+        self.i2c.writeto(self.address, bytes([byte]))