Mavrk Wireless Weather Station Communication System

By: Bill Gesner

GoalReceive weather information from two RJ-11

connectors(phone jacks).Transmit the data wirelessly from the Texas

Instrument micro Mavrk to a Texas Instrument Mavrk.

Send the data to a PC and a secondary embedded device.

Weather Meter DesignRain Gauge: The rain meter pools water

which causes a circuit to close once per 0.011” of rain.

Anemometer: The speed of the wind is recorded by closing a circuit once per rotation.

Wind Direction: The direction of the wind causes a change in resistance across the output.

Input circuit design

Rain Gauge InputA digital input port was used to detect the

current state of the circuit.The number of times the circuit was closed

was counted.Once every two seconds the count was

transmitted wirelessly to the base station.The data was sent to the PC via USB as well

as the serial port.

Wind Speed InputSimilar to the Rain gauge method.The Anemometer circuit closes once per

revolution. A wind speed of 2.4 km/h causes the switch to close once per second.

The amount of times the Anemometer circuit closed was counted and transmitted once every five seconds.

Wind Vane InputThe direction of the wind alters the

resistance across the wind vane output.An analog to digital converter input was used

to detect the voltage drop across the wind vane which was connected in series to a 10kOhm resistor.

The value of the ADC was transmitted wirelessly once every two seconds.

TemperatureA built in temperature sensor is included on

the micro Mavrk.The temperature sensor output is connected

to the ADC similar to the wind vane inputFunctionality of the temperature sensor is

optional to allow for the possibility of an extra ADC input.

HumidityA secondary chip can be attached to the

micro Mavrk to add humidity detection.The TMP-112 replaces the output of the built

in temperature sensor with the output of a humidity sensor.

The temperature data is then available via I2C with more precision.

LightThe brightness in the room can be read from

the micro Mavrk.This functionality can be enabled using the

standard micro Mavrk or the TMP-112.

OutputThe output of the data is then sent to the

Texas Instrument demonstration software “App Monitor”.

This displays all built in functionality such as temperature, humidity, and light levels.

The raw data is also transmitted serially via UART.

UART output packet structureThe data sent to secondary embedded

hardware required a data structure to ensure valid transmission.

In total 7 bytes were transmitted2 byte header1 byte to identify what sensor was

transmitting data2 bytes of data2 byte footer

ConclusionsThe mavrk system is a modular and versatile

development platform that can be used for swift prototyping.

The sparkfun weather station is straight forward and well documented

Code Composer is an easy to use and friendly environment.