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104 lines
3.6 KiB
ReStructuredText
104 lines
3.6 KiB
ReStructuredText
Custom I²C Device
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=================
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.. warning::
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Custom components are deprecated, not recommended for new configurations
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and will be removed from ESPHome in a future release.
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Please look at creating a real ESPHome component and "importing" it into your
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configuration with :doc:`/components/external_components`.
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You can find some basic documentation on creating your own components
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at :ref:`contributing_to_esphome`.
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Lots of devices communicate using the I²C protocol. If you want to integrate
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a device into ESPHome that uses this protocol you can pretty much use almost
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all Arduino-based code because the ``Wire`` library is also available in ESPHome.
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See the other custom component guides for how to register components and make
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them publish values.
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.. code-block:: cpp
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#include "esphome.h"
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class MyCustomComponent : public Component {
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public:
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void setup() override {
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// Initialize the device here. Usually Wire.begin() will be called in here,
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// though that call is unnecessary if you have an 'i2c:' entry in your config
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Wire.begin();
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}
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void loop() override {
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// Example: write the value 0x42 to register 0x78 of device with address 0x21
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Wire.beginTransmission(0x21);
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Wire.write(0x78);
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Wire.write(0x42);
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Wire.endTransmission();
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}
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};
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I²C Write
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---------
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It may be useful to write to a register via I²C using a numerical input. For example, the following yaml code snippet captures a user-supplied numerical input in the range 1--255 from the dashboard:
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.. code-block:: yaml
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number:
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- platform: template
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name: "Input 1"
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optimistic: true
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min_value: 1
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max_value: 255
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initial_value: 20
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step: 1
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mode: box
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id: input_1
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icon: "mdi:counter"
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We want to write this number to a ``REGISTER_ADDRESS`` on the slave device via I²C. The Arduino-based looping code shown above is modified following the guidance in :doc:`Custom Sensor Component </components/sensor/custom>`.
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.. code-block:: cpp
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#include "esphome.h"
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const uint16_t I2C_ADDRESS = 0x21;
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const uint16_t REGISTER_ADDRESS = 0x78;
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const uint16_t POLLING_PERIOD = 15000; //milliseconds
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char temp = 20; //Initial value of the register
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class MyCustomComponent : public PollingComponent {
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public:
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MyCustomComponent() : PollingComponent(POLLING_PERIOD) {}
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float get_setup_priority() const override { return esphome::setup_priority::BUS; } //Access I2C bus
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void setup() override {
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//Add code here as needed
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Wire.begin();
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}
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void update() override {
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char register_value = id(input_1).state; //Read the number set on the dashboard
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//Did the user change the input?
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if(register_value != temp){
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Wire.beginTransmission(I2C_ADDRESS);
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Wire.write(REGISTER_ADDRESS);
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Wire.write(register_value);
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Wire.endTransmission();
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temp = register_value; //Swap in the new value
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}
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}
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};
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The ``Component`` class has been replaced with ``PollingComponent`` and the free-running ``loop()`` is changed to the ``update()`` method with period set by ``POLLING_PERIOD``. The numerical value from the dashboard is accessed with its ``id`` tag and its state is set to the byte variable that we call ``register_value``. To prevent an I²C write on every iteration, the contents of the register are stored in ``temp`` and checked for a change. Configuring the hardware with ``get_setup_priority()`` is explained in :doc:`Step 1 </components/sensor/custom>`.
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See Also
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--------
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- :ghedit:`Edit`
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