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Added peripherals tutorial
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‎docs/source/_static/tutorials/peripherals/tutorial_peripheral_diagram.png

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‎docs/source/tutorials/peripherals.rst

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###########
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Peripherals
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###########
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Introduction
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------------
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This is a basic introduction on how the peripherals works on the ESP32. This tutorial can be used to understand
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on how to define the peripheral usage cross the pin definition on each of them.
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In some microcontrollers architecture, the peripherals are attached to specific pins and cannot be redefined to another one.
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For example.
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The *XYZ* MCU defines that the I2C peripheral SDA signal is the IO5 on the physical pin 10 and the SCL is on the IO6 and physical pin 11.
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This means that in your hardware project, you **NEED** to use these pins as the I2C ant this cannot be changed due the internal architecture.
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In this case, you must be very careful during the hardware design to not commit any mistake by switching the SDA and SCL connections. This
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will be impossible to solve by firmware.
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GPIO Matrix and Pin Mux
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-----------------------
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The ESP32 architecture includes the capability of configuring some peripherals to any of the GPIOs pins, managed by the `IO MUX GPIO`_.
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This capability, in sum, means that we can route the internal peripheral into a different phisycal pin using the IO MUX and the GPIO Matrix.
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.. figure:: ../_static/tutorials/peripherals/tutorial_peripheral_diagram.png
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:align: center
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:width: 600
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:figclass: align-center
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It means that in the scenario of the *XYZ* MCU, on the ESP32 we can use any of the GPIOs to route the SDA (input/output) and the SCL (output).
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To use this functionality, we must be aware of some precautions:
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* Some of the GPIOs are INPUT only.
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* Some peripherals has output signals and must be used on GPIO's capable to be configured as OUTPUT.
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* Some peripherals, mostly the high speed ones, ADC, DAC, Touch, and JTAG use dedicated GPIOs pins.
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.. warning::
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Before assigning the peripheral pins in your design, double check if the pins you're using are capable for that.
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The input only pins cannot be used for peripherals that requires output or input/output signals.
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The biggest advantage of this is the fact that we don't need to be fully dependent on the physical pin, since we can change according to our needs
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and this can facilitate on the hardware design routing or in some cases, fix some pin swap mistake during the hardware design phase.
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Peripherals
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-----------
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Here is the basic peripheral list present on the ESP32. The peripheral list may vary from each ESP32 SoC family.
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To see all peripherals available on the ESP32-S2 and ESP32-C3, check each of the datasheet.
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Peripheral Table
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****************
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============================== ===================================
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Type Function
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============================== ===================================
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ADC Dedicated GPIOs
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DAC Dedicated GPIOs
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Touch Sensor Dedicated GPIOs
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JTAG Dedicated GPIOs
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SD/SDIO/MMC HostController Dedicated GPIOs
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Motor PWM Any GPIO
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SDIO/SPI SlaveController Dedicated GPIOs
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UART Any GPIO
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I2C Any GPIO
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I2S Any GPIO
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LED PWM Any GPIO
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RMT Any GPIO
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GPIO Any GPIO
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Parallel QSPI Dedicated GPIOs
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EMAC Dedicated GPIOs
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Pulse Counter Any GPIO
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TWAI Any GPIO
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============================== ===================================
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This table is present on each datasheet provided by Espressif.
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Usage Examples
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--------------
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On the Arduino Uno, we have the I2C pins defined by hardware, A4 is the SDA and A5 the SCL. In this case we do not need to set
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those pins in the ```Wire.begin();``` function, because they are already into the Wire library.
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.. code-block:: arduino
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void setup()
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{
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Wire.begin(); // join i2c bus (address optional for master)
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}
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Now for the ESP32, the default pins for the I2C GPIO21 for SDA and GPIO22 for SCL, but we can use a different pin as alternative for the
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default ones.
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To change the pins, we must call the ```Wire.setPins(int sda, int scl);``` function before calling ```Wire.begin();```.
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.. code-block:: arduino
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void setup()
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{
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Wire.setPins(sda_pin, scl_pin);
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Wire.begin(); // join i2c bus (address optional for master)
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}
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A similar approach also applies for the other peripherals.
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Resources
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---------
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* `ESP32 Datasheet`_ (Datasheet)
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* `ESP32-S2 Datasheet`_ (Datasheet)
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* `ESP32-C3 Datasheet`_ (Datasheet)
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.. _Espressif Systems: https://www.espressif.com
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.. _Espressif Product Selector: https://products.espressif.com/
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.. _ESP32 Datasheet: https://www.espressif.com/sites/default/files/documentation/esp32_datasheet_en.pdf
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.. _ESP32-S2 Datasheet: https://www.espressif.com/sites/default/files/documentation/esp32-s2_datasheet_en.pdf
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.. _ESP32-C3 Datasheet: https://www.espressif.com/sites/default/files/documentation/esp32-c3_datasheet_en.pdf
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.. _IO MUX GPIO: https://www.espressif.com/sites/default/files/documentation/esp32_technical_reference_manual_en.pdf#iomuxgpio
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‎docs/source/tutorials/tutorials.rst

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Basic <basic>
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DFU <dfu>
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Peripherals (GPIO mapping) <peripherals>

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