Add bias setting

displayio_st7565.py

@@ -32,7 +32,7 @@
 
 
 _INIT_SEQUENCE = (
-    b"\xA3\x00"  # LCD bias select
+    b"\xA3\x00"  # LCD bias select (default 1/7)
     b"\xA1\x00"  # ADC select
     b"\xC0\x00"  # SHL select
     b"\x40\x00"  # Initial display line
@@ -45,6 +45,9 @@
     b"\x81\x01\x00"  # Set initial contrast
 )
 
+BIAS_7 = 0xA3
+BIAS_9 = 0xA2
+
 
 class ST7565(BusDisplay):
     """ST7565 and ST7567 display driver"""
@@ -63,8 +66,21 @@ def __init__(self, bus: FourWire, **kwargs) -> None:
             pixels_in_byte_share_row=False,
         )
 
+        self._bias = 0
         self._contrast = 0
 
+    @property
+    def bias(self) -> int:
+        return self._bias
+
+    @bias.setter
+    def bias(self, bias: int) -> None:
+        if bias not in (BIAS_7, BIAS_9):
+            raise ValueError("bias setting must be either displayio_st7565.BIAS_7 or displayio_st7565.BIAS_9")
+
+        self._bias = bias
+        self.bus.send(self._bias)
+
     @property
     def contrast(self) -> int:
         return self._contrast