esphome-docs/cookbook/uart_text_sensor.rst
2021-05-03 22:55:12 +12:00

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Custom UART Text Sensor
=======================
.. seo::
:description: Instructions for setting up a custom uart text sensor.
:image: language-cpp.png
Lots of devices communicate using the UART protocol. If you want to read
lines from uart to a Text Sensor you can do so using this code example.
With this you can use automations or lambda to set switch or sensor states.
.. code-block:: cpp
#include "esphome.h"
class UartReadLineSensor : public Component, public UARTDevice, public TextSensor {
public:
UartReadLineSensor(UARTComponent *parent) : UARTDevice(parent) {}
void setup() override {
// nothing to do here
}
int readline(int readch, char *buffer, int len)
{
static int pos = 0;
int rpos;
if (readch > 0) {
switch (readch) {
case '\n': // Ignore new-lines
break;
case '\r': // Return on CR
rpos = pos;
pos = 0; // Reset position index ready for next time
return rpos;
default:
if (pos < len-1) {
buffer[pos++] = readch;
buffer[pos] = 0;
}
}
}
// No end of line has been found, so return -1.
return -1;
}
void loop() override {
const int max_line_length = 80;
static char buffer[max_line_length];
while (available()) {
if(readline(read(), buffer, max_line_length) > 0) {
publish_state(buffer);
}
}
}
};
(Store this file in your configuration directory, for example ``uart_read_line_sensor.h``)
And in YAML:
.. code-block:: yaml
# Example configuration entry
esphome:
includes:
- uart_read_line_sensor.h
logger:
level: VERBOSE #makes uart stream available in esphome logstream
baud_rate: 0 #disable logging over uart
uart:
id: uart_bus
tx_pin: D0
rx_pin: D1
baud_rate: 9600
text_sensor:
- platform: custom
lambda: |-
auto my_custom_sensor = new UartReadLineSensor(id(uart_bus));
App.register_component(my_custom_sensor);
return {my_custom_sensor};
text_sensors:
id: "uart_readline"
Example usage
-------------
Here is an example switch using the uart text sensor to set switch state.
Here we use interval to request status from the device. The response will be stored in uart text sensor.
Then the switch uses the text sensor state to set its own state.
.. code-block:: yaml
switch:
- platform: template
name: "Switch"
lambda: |-
if (id(uart_readline).state == "*POW=ON#") {
return true;
} else if(id(uart_readline).state == "*POW=OFF#") {
return false;
} else {
return {};
}
turn_on_action:
- uart.write: "\r*pow=on#\r"
turn_off_action:
- uart.write: "\r*pow=off#\r"
interval:
- interval: 10s
then:
- uart.write: "\r*pow=?#\r"
See Also
--------
- :doc:`/components/uart`
- :doc:`/custom/uart`
- :ghedit:`Edit`