Docs for CS Optional (#644)

* Docs for CS Optional

* rst fix

Co-authored-by: Ilya Goldberg <iggie@mac.com>
Co-authored-by: Guillermo Ruffino <glm.net@gmail.com>

components/binary_sensor/pn532.rst

@@ -47,8 +47,8 @@ to have an :ref:`spi bus <spi>` in your configuration with both the **miso_pin**
 Configuration variables:
 ************************
 
-- **cs_pin** (**Required**, :ref:`Pin Schema <config-pin_schema>`): The pin on the ESP that the chip select line
-  is connected to.
+- **cs_pin** (*Optional*, :ref:`Pin Schema <config-pin_schema>`): The pin on the ESP that that the CS line is connected to.
+  The CS line can be connected to GND if this is the only device on the SPI bus.
 - **update_interval** (*Optional*, :ref:`config-time`): The duration of each scan on the PN532. This affects the
   duration that the individual binary sensors stay active when they're found.
   If a device is not found within this time window, it will be marked as not present. Defaults to 1s.

components/display/max7219.rst

@@ -19,7 +19,7 @@ with ESPHome. Please note that this integration is *only* for 7-segment display,
 As the communication with the MAX7219 is done using SPI for this integration, you need
 to have an :ref:`SPI bus <spi>` in your configuration with both the **mosi_pin** set (miso_pin is not required).
 Connect VCC to 3.3V (the manufacturer recommends 4+ V, but 3.3V seems to work fine), DIN to your ``mosi_pin`` and
-CS to your set ``cs_pin`` and finally GND to GND.
+CS to your set ``cs_pin`` (or to GND if this is the only device on the SPI bus) and finally GND to GND.
 
 You can even daisy-chain multiple MAX7219s by connecting the DOUT of the previous chip in the chain to the
 next DIN. With more than ~3 chips the 3.3V will probably not be enough, so then you will have to potentially
@@ -42,7 +42,8 @@ use a logic level converted.
 Configuration variables:
 ------------------------
 
-- **cs_pin** (**Required**, :ref:`Pin Schema <config-pin_schema>`): The pin you have the CS line hooked up to.
+- **cs_pin** (*Optional*, :ref:`Pin Schema <config-pin_schema>`): The pin on the ESP that that the CS line is connected to.
+  The CS line can be connected to GND if this is the only device on the SPI bus.
 - **num_chips** (*Optional*, integer): The number of chips you wish to use for daisy chaining. Defaults to
   ``1``.
 - **intensity** (*Optional*, integer): The intensity with which the MAX7219 should drive the outputs. Range is from

components/display/ssd1306.rst

@@ -92,9 +92,9 @@ If your SSD1306 or SH1106 is connected via the :ref:`I²C Bus <i2c>`, see :ref:`
     SSD1306 OLED Display
 
 Connect D0 to the CLK pin you chose for the :ref:`SPI bus <spi>`, connect D1 to the MOSI pin and ``DC`` and ``CS``
-to some GPIO pins on the ESP. For power, connect
-VCC to 3.3V and GND to GND. Optionally you can also connect the ``RESET`` pin to a pin on the ESP which may
-improve reliability.
+to some GPIO pins on the ESP. If this is the only device on the SPI bus, the ``CS`` pin can be connected to GND.
+For power, connect VCC to 3.3V and GND to GND.
+Optionally you can also connect the ``RESET`` pin to a pin on the ESP which may improve reliability.
 
 .. code-block:: yaml
 
@@ -126,7 +126,8 @@ Configuration variables:
   - ``SH1106 96x16``
   - ``SH1106 64x48``
 
-- **cs_pin** (**Required**, :ref:`Pin Schema <config-pin_schema>`): The Chip Select (CS) pin.
+- **cs_pin** (*Optional*, :ref:`Pin Schema <config-pin_schema>`): The pin on the ESP that that the CS line is connected to.
+  The CS line can be connected to GND if this is the only device on the SPI bus.
 - **dc_pin** (**Required**, :ref:`Pin Schema <config-pin_schema>`): The DC pin.
 - **reset_pin** (*Optional*, :ref:`Pin Schema <config-pin_schema>`): The RESET pin. Defaults to not connected.
 - **rotation** (*Optional*): Set the rotation of the display. Everything you draw in ``lambda:`` will be rotated

components/display/ssd1325.rst

@@ -51,7 +51,8 @@ Configuration variables:
   - ``SSD1325 64x48``
 
 - **reset_pin** (:ref:`Pin Schema <config-pin_schema>`): The RESET pin.
-- **cs_pin** (:ref:`Pin Schema <config-pin_schema>`): The CS pin.
+- **cs_pin** (*Optional*, :ref:`Pin Schema <config-pin_schema>`): The pin on the ESP that that the CS line is connected to.
+  The CS line can be connected to GND if this is the only device on the SPI bus.
 - **dc_pin** (:ref:`Pin Schema <config-pin_schema>`): The DC pin.
 - **lambda** (*Optional*, :ref:`lambda <config-lambda>`): The lambda to use for rendering the content on the display.
   See :ref:`display-engine` for more information.

components/display/waveshare_epaper.rst

@@ -66,7 +66,8 @@ configuration.
 Configuration variables:
 ------------------------
 
-- **cs_pin** (**Required**, :ref:`Pin Schema <config-pin_schema>`): The CS pin.
+- **cs_pin** (*Optional*, :ref:`Pin Schema <config-pin_schema>`): The pin on the ESP that that the CS line is connected to.
+  The CS line can be connected to GND if this is the only device on the SPI bus.
 - **dc_pin** (**Required**, :ref:`Pin Schema <config-pin_schema>`): The DC pin.
 - **model** (**Required**): The model of the E-Paper display. Options are:
 

components/sensor/atm90e32.rst

@@ -36,7 +36,9 @@ The `CircuitSetup Expandable 6 Channel Energy Meter <https://circuitsetup.us/ind
 Configuration variables:
 ------------------------
 
-- **cs_pin** (**Required**, :ref:`Pin Schema <config-pin_schema>`): The pin CS is connected to. For the 6 channel meter main board, this will always be 5 and 4. For the add-on boards a jumper can be selected for each CS pin, but default to 0 and 16.
+- **cs_pin** (**Required**, :ref:`Pin Schema <config-pin_schema>`): The pin CS is connected to. For the 6 channel
+  meter main board, this will always be 5 and 4. For the add-on boards a jumper can be selected for each CS pin,
+  but default to 0 and 16.
 - **line_frequency** (**Required**, string): The AC line frequency of the supply voltage. One of ``50Hz``, ``60Hz``.
 - **phase_a** (*Optional*): The configuration options for the 1st phase.
 

components/sensor/max31855.rst

@@ -35,7 +35,8 @@ Configuration variables:
 ------------------------
 
 - **name** (**Required**, string): The name for the temperature sensor.
-- **cs_pin** (**Required**, :ref:`Pin Schema <config-pin_schema>`): The Chip Select pin of the SPI interface.
+- **cs_pin** (*Optional*, :ref:`Pin Schema <config-pin_schema>`): The pin on the ESP that that the CS line is connected to.
+  The CS line can be connected to GND if this is the only device on the SPI bus.
 - **update_interval** (*Optional*, :ref:`config-time`): The interval to check the sensor. Defaults to ``60s``.
 - **reference_temperature** (*Optional*, :ref:`Sensor <config-sensor>`): Access the internal temperature sensor of the MAX31855. Requires a **name** and/or **id**.
 - **spi_id** (*Optional*, :ref:`config-id`): Manually specify the ID of the :ref:`SPI Component <spi>` if you want to use multiple SPI buses.

components/sensor/max6675.rst

@@ -43,7 +43,8 @@ Configuration variables:
 ------------------------
 
 - **name** (**Required**, string): The name for the temperature sensor.
-- **cs_pin** (**Required**, :ref:`Pin Schema <config-pin_schema>`): The Chip Select pin of the SPI interface.
+- **cs_pin** (*Optional*, :ref:`Pin Schema <config-pin_schema>`): The pin on the ESP that that the CS line is connected to.
+  The CS line can be connected to GND if this is the only device on the SPI bus.
 - **update_interval** (*Optional*, :ref:`config-time`): The interval to check the sensor. Defaults to ``60s``.
 
 - **spi_id** (*Optional*, :ref:`config-id`): Manually specify the ID of the :ref:`SPI Component <spi>` if you want

components/spi.rst

@@ -13,7 +13,8 @@ SPI is a very common high-speed protocol for a lot of devices. The SPI bus usual
 - **CLK**: Is used to tell the receiving device when to read data. All devices on the bus can
   share this line. Sometimes also called ``SCK``.
 - **CS** (chip select): Is used to tell the receiving device when it should listen for data. Each device has
-  an individual CS line. Sometimes also called ``SS``.
+  an individual CS line. Sometimes also called ``SS``. If the SPI bus has a single device, it's CS pin
+  can usually be connected to ground to tell it that it is allways selected.
 - **MOSI** (also DIN): Is used to send data from the master (the ESP) to the receiving device. All devices on the bus can
   share this line.
 - **MISO** (also DOUT): Is used to receive data. All devices on the bus can