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The EYWeather GPRS based APRS WX has been successfully deployed in Park Rynie on the Natal South Coast. The unit was designed as an experimental APRS WX that is based on the EYTraker PCB and PIC software framework. Very similar in design to the EYTraker, EYWeather has the same underlying PIC software without the GPS engine included in the design.

Design Highlights

Due to the huge amount of programming that went into the EYTraker software development, the software adaptation, to enable the PIC to function as a WX, was completed in under a month. The most challenging part of the software design was the implementation of the Dallas One-Wire (R) interface in the PIC software. The PIC employs a ROM code reader which enables any Dallas One-wire weather station to be used with the EYWeather unit. The humidity and barometric sensor is read using the PIC's onboard ADC's. The DS 1307 RTC is read via a standard SPI interface. Similar to EYTraker, a PIC18F252 running at 4 MHz is used.

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The Station features a real time clock, implemented as a DS1307 RTC unit programmed to Zulu time, including the date and year function for APRS packet time stamping.

I have added a second PIC to decode incoming APRS data packets. The PIC16F628 will respond to the stations callsign and acknowledge messages sent to the WX and certain messages functions, including the Query function in UIView has been implemented in software. The PIC runs on its internal crystal at 4 MHz

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The following messages are available: 1234>Tmp       Returns the real-time temp with UTC time stamp

                                                             1234>Bar        Returns the real-time barometric pressure with UTC time stamp

                                                             1234>Pct        Returns a full APRS WX packet

The 1234> portion is the current password and the > is a password/message separator. It has to be included in front of the message in UIView as per the example above.

The WX is programmed to transmit the standard APRS WX packet every 5 minutes 24 hours a day. The AAG based rain gauge is already implemented in software, but has not yet been added to the WX in Park Rynie. The hourly rain is displayed together with a rain accumulator in the additional packet payload just after the supply voltage indication.

The WX also features a LCD display for local indication of weather conditions.

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The WX will measure and display: UTC time, Date, Current Temp, Humidity, Barometric pressure, Wind Speed, Wind Direction, Wind Gust (Reset every 5 minutes), Supply Voltage and Rain Accumulation.

The APRS Weather station uses a Honeywell HIH4000 humidity sensor, a Motorola MPX4115A absolute pressure sensor.

The temperature is measured with a DS1820, Wind speed with a DS2423 and wind direction with a DS2450. All three these sensor is connected on a common 1-wire bus. The WX uses the TAI8515 1-Wire Weather Instrument Kit V3.0

More on this instrument can be found at http://www.aagelectronica.com/aag/index.html

The front of the WX has a standard 20 x 4 LCD display and status LED's.

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The rear of the unit has connections for power, the GSM antenna, 1-wire RJ-11 socket and Humidity/Barometric J-11 socket and the DB9 socket for bootloading new software and PC software configuration functions.

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The station is called PRYNIE. Have a look for the beacon on UIView somewhere on the south coast of Natal.

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Until later...