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106 lines
4.4 KiB
Markdown
106 lines
4.4 KiB
Markdown
# Temperature sensors
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It is now possible to measure temperatures with the help of the I²C LM75 and 1-Wire DS18B20 chips. The temperature values can be displayed on the OSD and they are also logged. A total maximum of 8 temperature sensors can be connected. The support is enabled by default on F4 and F7 FCs. To use with F3 FCs you need to build a custom firmware.
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## LM75
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Up to 8 can be connected to the flight controller.
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* Package: SOP-8, breakout boards can be found easily
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* Interface: I²C (**max 400kHz**)
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* Supply: 2.7 to 5.5V
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* Temperature range: -55 to +125°C
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On the purple LM75 (CJMCU-75), address line pins on the bottom of the PCB need to be bridged either to ground or VCC (to define I2C address)
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Pin definition:
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| A2 | A1 | A0 |Address|INAV add|
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|-----|-----|-----|-------|--------|
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| GND | GND | GND | 0x48 | 0 |
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| GND | GND | VCC | 0x49 | 1 |
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| GND | VCC | GND | 0x4A | 2 |
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| GND | VCC | VCC | 0x4B | 3 |
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| VCC | GND | GND | 0x4C | 4 |
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| VCC | GND | VCC | 0x4D | 5 |
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| VCC | VCC | GND | 0x4E | 6 |
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| VCC | VCC | VCC | 0x4F | 7 |
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If more than one sensor is used, each sensor must have different address.
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## DS18B20
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* Package: TO-92, SO-8, µSOP-8
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* Interface: 1-Wire
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* Supply: 3.0 to 5.5V (parasitic power not supported)
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* Temperature range: -55 to +125°C
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None of the flight controllers on the market at the time this documentation is written supports 1-Wire directly. To use these sensors a I²C to 1-Wire interface chip needs to be used, the DS2482. Connect the DS2482 SCL and SDA lines to your FC, add a 4.7kohm pull-up resistor between VCC and the DQ pin then connect all the sensors DQ pin to the DS2482 DQ pin.
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## Configuring temperature sensors
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The `temp_sensor` CLI command can be used to display and change the temperature sensors configuration. When a new temperature sensor is connected it is automatically detected and will appear in the output of the `temp_sensor` command.
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* `temp_sensor` without any argument displays all the sensors configuration
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* `temp_sensor reset` deletes all the sensors
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* `temp_sensor index type address alarm_min alarm_max osd_symbol label` to configure a new sensor or modify the configuration of an existing one.
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### Parameters description
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* `index` is the index of the configuration slot you want to change
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* `type` can be `1` for LM75 or `2` for DS18B20
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* `address` is the address of the device on the bus. 0 to 7 for a LM75 or the full 64bit ROM in hex format for a 18B20
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* `alarm_min` is the temperature under which the corresponding OSD element will start blinking (decidegrees centigrade)
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* `alarm_max` is the temperature above which the corresponding OSD element will start blinking (decidegrees centigrade)
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* `osd_symbol` is the ID of a symbol to display on the OSD to the left of the temperature value. Use 0 to display a label instead (see next parameter). See the table bellow for the available IDs
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* `label` is a 4 characters maximum label that is displayed on the OSD next to the temperature value
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| Symbol ID | Description |
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|-----------|-----------------------------|
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| 1 | Generic temperature symbol |
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| 2 | ESC temperature symbol |
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| 3 | VTX temperature symbol |
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| 4 | Motor temperature symbol |
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| 5 | Battery temperature symbol |
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| 6 | Exterior temperature symbol |
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### Example output
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Example output of the `temp_sensor` command on a system with two LM75 and four DS18B20 sensors connected
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```
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temp_sensor 0 1 0 -200 600 0
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temp_sensor 1 1 1 -200 600 0
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temp_sensor 2 2 7c0118681e1cff28 -200 600 0
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temp_sensor 3 2 7d01186838f2ff28 -200 600 0
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temp_sensor 4 2 210118684001ff28 -200 600 0
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temp_sensor 5 2 f801186750c7ff28 -200 600 0
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temp_sensor 6 0 0 0 0
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temp_sensor 7 0 0 0 0
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```
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To set for example the OSD symbol of the first temperature sensor to the ESC symbol:
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`temp_sensor 0 1 0 -200 600 2`
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To change for example the configuration of the fourth sensor to label `BATT`, minimum value alarm 0.5°C and maximum value alarm 45°C
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`temp_sensor 3 2 7d01186838f2ff28 5 450 0 BATT`
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## Configuring the way OSD temperature labels are displayed
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You can use the `osd_temp_label_align` setting to chose how the labels for the temperature sensor's values are displayed. Possible alignment values are `LEFT` and `RIGHT`.
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### Example
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```
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LEFT alignment:
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T1 xxx°C
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ESC xxx°C
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RIGHT alignment:
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T1 xxx°C
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ESC xxx°C
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```
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