153 lines
3.8 KiB
Markdown
153 lines
3.8 KiB
Markdown
# Si7021 Module
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| Since | Origin / Contributor | Maintainer | Source |
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| :----- | :-------------------- | :---------- | :------ |
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| 2017-04-19 | [fetchbot](https://github.com/fetchbot) | [fetchbot](https://github.com/fetchbot) | [si7021.c](../../../app/modules/si7021.c)|
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This module provides access to the Si7021 humidity and temperature sensor.
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## si7021.firmware()
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Read the internal firmware revision of the Si7021 sensor.
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#### Syntax
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`si7021.firmware()`
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#### Parameters
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none
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#### Returns
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`fwrev` Firmware version
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* `0xFF` Firmware version 1.0
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* `0x20` Firmware version 2.0
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#### Example
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```lua
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local sda, scl = 6, 5
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i2c.setup(0, sda, scl, i2c.SLOW) -- call i2c.setup() only once
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si7021.setup()
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fwrev = si7021.firmware()
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print(string.format("FW: %X\r\n", fwrev))
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```
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## si7021.setting()
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Settings for the sensors configuration register to adjust measurement resolution, on-chip heater and read the supply voltage status.
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#### Syntax
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`si7021.setting(RESOLUTION[, HEATER, HEATER_SETTING])`
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#### Parameters
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- `RESOLUTION`
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* `si7021.RH12_TEMP14` Relative Humidity 12 bit - Temperature 14 bit (default)
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* `si7021.RH08_TEMP12` Relative Humidity 8 bit - Temperature 12 bit
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* `si7021.RH10_TEMP13` Relative Humidity 10 bit - Temperature 13 bit
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* `si7021.RH11_TEMP11` Relative Humidity 11 bit - Temperature 11 bit
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- `HEATER` optional
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* `si7021.HEATER_ENABLE` On-chip Heater Enable
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* `si7021.HEATER_DISABLE` On-chip Heater Disable (default)
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- `HEATER_SETTING` optional
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* `0x00` - `0x0F` 3.09 mA - 94.20 mA
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#### Returns
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- `resolution`
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* `0` Relative Humidity 12 bit - Temperature 14 bit
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* `1` Relative Humidity 8 bit - Temperature 12 bit
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* `2` Relative Humidity 10 bit - Temperature 13 bit
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* `3` Relative Humidity 11 bit - Temperature 11 bit
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- `vdds`
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* `0` VDD OK (1.9V - 3.6V)
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* `1` VDD LOW (1.8V - 1.9V)
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- `heater`
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* `0` Disabled
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* `1` Enabled
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- `heater_setting`
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* `0` - `15`
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#### Example
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```lua
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local id, sda, scl = 0, 6, 5
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i2c.setup(id, sda, scl, i2c.SLOW) -- call i2c.setup() only once
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si7021.setup()
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res, vdds, heater, heater_set = si7021.setting(si7021.RH12_TEMP14)
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res, vdds, heater, heater_set = si7021.setting(si7021.RH12_TEMP14, si7021.HEATER_ENABLE, 0x01)
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```
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## si7021.setup()
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Initializes the device on fixed I²C device address (0x40).
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#### Syntax
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`si7021.setup()`
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#### Parameters
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none
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#### Returns
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`nil`
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#### Example
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```lua
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local sda, scl = 6, 5
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i2c.setup(0, sda, scl, i2c.SLOW) -- call i2c.setup() only once
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si7021.setup()
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```
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## si7021.read()
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#### Syntax
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`si7021.read()`
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#### Parameters
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none
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#### Returns
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- `hum` humidity (see note below)
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- `temp` temperature (see note below)
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- `hum_dec` humidity decimal
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- `temp_dec` temperature decimal
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!!! note
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If using float firmware then `hum` and `temp` are floating point numbers. On an integer firmware, the final values have to be concatenated from `hum` and `hum_dec` / `temp` and `temp_dec`.
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#### Example
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```lua
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local sda, scl = 6, 5
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i2c.setup(0, sda, scl, i2c.SLOW) -- call i2c.setup() only once
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si7021.setup()
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hum, temp, hum_dec, temp_dec = si7021.read()
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-- Integer firmware using this example
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print(string.format("Humidity:\t\t%d.%03d\nTemperature:\t%d.%03d\n", hum, hum_dec, temp, temp_dec))
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-- Float firmware using this example
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print("Humidity: "..hum.."\n".."Temperature: "..temp)
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```
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## si7021.serial()
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Read the individualized 64-bit electronic serial number of the Si7021 sensor.
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#### Syntax
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`si7021.serial()`
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#### Parameters
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none
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#### Returns
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- `sna` 32-bit serial number part a
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- `snb` 32-bit serial number part b, upper byte contains the device identification
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* `0x00` or `0xFF` engineering samples
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* `0x0D` `13` Si7013
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* `0x14` `20` Si7020
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* `0x15` `21` Si7021
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#### Example
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```lua
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local sda, scl = 6, 5
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i2c.setup(0, sda, scl, i2c.SLOW) -- call i2c.setup() only once
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si7021.setup()
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sna, snb = si7021.serial()
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print(string.format("SN:\t\t%X%X\nDevice:\tSi70%d", sna, snb, bit.rshift(snb,24)))
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```
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