st7789 drivers: provide default rst arg.

DRIVERS.md

@@ -427,7 +427,8 @@ below. An example file for the Pi Pico is in `setup_examples/st7789_pico.py`.
  electrical issues such as lead lengths, PCB layout and grounding.
  * `cs` An initialised output pin. Initial value should be 1.
  * `dc` An initialised output pin. Initial value should be 0.
- * `rst` An initialised output pin. Initial value should be 1.
+ * `rst=None` An initialised output pin with initial value 1. The default is for
+ vendors who do not provide an `rst` connection.
  * `height=240` Display dimensions in pixels. For portrait mode exchange
  `height` and `width` values: this ensures that `nano-gui` gets the correct
  aspect ratio.

drivers/st7789/st7789_4bit.py

@@ -81,7 +81,7 @@ class ST7789(framebuf.FrameBuffer):
         spi,
         cs,
         dc,
-        rst,
+        rst=None,
         height=240,
         width=240,
         disp_mode=LANDSCAPE,
@@ -114,13 +114,14 @@ class ST7789(framebuf.FrameBuffer):
 
     # Hardware reset
     def _hwreset(self):
-        self._dc(0)
-        self._rst(1)
-        sleep_ms(1)
-        self._rst(0)
-        sleep_ms(1)
-        self._rst(1)
-        sleep_ms(1)
+        if self._rst is not None:
+            self._dc(0)
+            self._rst(1)
+            sleep_ms(1)
+            self._rst(0)
+            sleep_ms(1)
+            self._rst(1)
+            sleep_ms(1)
 
     # Write a command, a bytes instance (in practice 1 byte).
     def _wcmd(self, buf):

drivers/st7789/st7789_8bit.py

@@ -70,7 +70,7 @@ class ST7789(framebuf.FrameBuffer):
         spi,
         cs,
         dc,
-        rst,
+        rst=None,
         height=240,
         width=240,
         disp_mode=LANDSCAPE,
@@ -103,13 +103,14 @@ class ST7789(framebuf.FrameBuffer):
 
     # Hardware reset
     def _hwreset(self):
-        self._dc(0)
-        self._rst(1)
-        sleep_ms(1)
-        self._rst(0)
-        sleep_ms(1)
-        self._rst(1)
-        sleep_ms(1)
+        if self._rst is not None:
+            self._dc(0)
+            self._rst(1)
+            sleep_ms(1)
+            self._rst(0)
+            sleep_ms(1)
+            self._rst(1)
+            sleep_ms(1)
 
     # Write a command, a bytes instance (in practice 1 byte).
     def _wcmd(self, buf):