Si702x

This library provides a driver class for the Si702x temperature/humidity sensor. This class is compatible with the Si7020 and Si7021 — they differ only in measurement accuracy. Both sensors connect over I²C.

You can view the library’s source code on GitHub. Click here to see information on other versions of this library.

To include this library in your project, add #require "Si702x.device.lib.nut:2.0.1" at the top of your device code

Hardware

The Si702x should be connected as follows:

Class Usage

Constructor: Si702x(impI2Cbus[, baseAddress])

Parameters

Parameter	Type	Required	Description
impI2Cbus	i2c object	Yes	The configured I²C bus to which the sensor is connected
baseAddress	Integer	No	The sensor’s I²C address. Default: 0x80

Example

#require "Si702x.device.lib.nut:2.0.1"

// Configure the I2C bus on the imp001
hardware.i2c89.configure(CLOCK_SPEED_400_KHZ);

// Instantiate the sensor driver
tempHumid <- Si702x(hardware.i2c89);

Class Methods

read([callback])

This method takes a sensor reading. It can operate synchronously or asynchronously.

For synchronous operation, pass null or provide no argument.

For asynchronous operation, pass in a callback function. The callback should have one parameter of its own, results, which will receive the table (see Return Value, below) that is returned by the method in synchronous mode.

Parameters

Parameter	Type	Required	Description
callback	Function	No	An optional callback function which will receive the reading. Default: null

Return Value

Table — the sensor reading results with the keys listed below, or nothing if the method is configured to run asynchronously.

Results Table Key	Type	Slot Always Present?	Description
err	String	No	If present, an error message
temperature	Float	Yes	Temperature in Celsius, or null if an error occurred
humidity	Float	Yes	Relative humidity as a percentage, or null if an error occurred

Note The err key will only be present if an error occurred. You should check for the existence of err before using the results.

Example

function printResult(result) {
    if ("err" in result) {
        server.log(result.err);
    } else {
        server.log(format("Temperature: %.01f°C, Relative Humidity: %.01f%%", result.temperature, result.humidity));
    }
}

// Take a reading and print the result
tempHumid.read(printResult);

Release History

The Electric Imp Dev Center documents the latest version of the library. For past versions, please see the Electric Imp public GitHub repos listed below.

Version	Source Code	Notes
1.0.0	GitHub	Initial release
2.0.0	GitHub	Change library name to reflect new naming scheme; fixed write register bug in the init() method
2.0.1	GitHub	Moved static variables to enum; make sync and async reading/error results the same

License

This library is licensed under the MIT License.