[sn74hc595 ] SPI config (#3341)

components/sn74hc595.rst

@@ -6,9 +6,10 @@ SN74HC595 I/O Expander (shift register)
 
 The SN74HC595 component allows you to use SN74HC595 shift registers as I/O expanders
 (`datasheet <http://www.ti.com/lit/ds/symlink/sn74hc595.pdf>`__,
-`SparkFun`_) in ESPHome. It uses 3 wires (optionally 4) for communication.
+`SparkFun`_) in ESPHome. It uses 3 wires (optionally 4) for communication. Optionally, it can be added
+to a SPI bus to allow sharing pins with other components.
 
-Once configured, you can use any of the 8 pins for your projects. Up-to 256 shift registers can be daisy-chained
+Once configured, you can use any of the 8 pins for your projects. Up to 256 shift registers can be daisy-chained
 to provide more pins, without using more GPIO pins on the controller.
 
 Use of the OE pin is optional. If used, the pin should be pulled up externally.
@@ -21,6 +22,11 @@ Use of the OE pin is optional. If used, the pin should be pulled up externally.
 
 .. _SparkFun: https://www.sparkfun.com/products/13699
 
+The component can be configured using :ref:`GPIO pins <config-pin_schema>` or the :ref:`SPI Bus <spi>`.
+
+Over GPIO
+---------
+
 .. code-block:: yaml
 
     # Example configuration entry
@@ -53,6 +59,46 @@ Configuration variables:
 - **sr_count** (*Optional*, int): Number of daisy-chained shift registers, up-to 256. Defaults to ``1``.
 
 
+Pin configuration variables:
+****************************
+
+- **sn74hc595** (**Required**, :ref:`config-id`): The id of the SN74HC595 component the pin belongs to.
+- **number** (**Required**, int): The pin number.
+- **inverted** (*Optional*, boolean): If all written values should be treated as inverted.
+  Defaults to ``false``.
+
+Over SPI
+--------
+
+.. code-block:: yaml
+
+    # Example configuration entry
+    spi:
+    sn74hc595:
+      - id: 'sn74hc595_hub'
+        latch_pin: D7
+        oe_pin: D6
+        sr_count: 2
+
+    # Individual outputs
+    switch:
+      - platform: gpio
+        name: "SN74HC595 Pin #0"
+        pin:
+          sn74hc595: sn74hc595_hub
+          # Use pin number 0
+          number: 0
+          inverted: false
+
+Configuration variables:
+************************
+
+- **id** (**Required**, :ref:`config-id`): The id to use for this SN74HC595 component.
+- **latch_pin** (**Required**, :ref:`Pin Schema <config-pin_schema>`): Pin connected to SN74HC595 RCLK (ST_CP) pin
+- **oe_pin** (*Optional*, :ref:`Pin Schema <config-pin_schema>`): Pin connected to SN74HC595 OE pin
+- **sr_count** (*Optional*, int): Number of daisy-chained shift registers, up to 256. Defaults to ``1``.
+
+
 Pin configuration variables:
 ****************************