System Board

DSC01450The main system board, just slightly bigger than a business card, is based on a PIC24FJ256 device. A 16-bit MCU running at 32 Mhz . The chip has 256Kb of flash and lots of IO pins  and built in peripherals.  A 512Kb EE-PROM serves as the permanent storage  for the embedded webpages.

The rear side of the board holds a CAT5 connector which is used for the cabling up to the outlaying sensors.  The 5 pin white  connector on the bottom is  for the Baro/Hygro/Temp board.  One of the 3 pin connectors is for a 5V power supply feed, and one is a 5V DSC01451connection for an enclosure  fan.  The top of the board has connectors for an USB / UART bridge , rain bucket and solar sensor.

Power consumption with the air-data sensors attached is between  0.675 and 0.75 Watt depending  on the frequency of WiFi traffic. A complete station with air data and wind sensors, but without an aspiration fan runs on 7/8 of a Watt.

The row of pins extending on both sides allow for two add-on expansion boards.

Since setting up a WiFi based device can be  somewhat of a catch 22,  a  USB/UART  COMn device allows for a Windows PC application to setup the WiFi connection parameters in order to bootstrap the WiFi connection. A device driver needs to be installed to recognize the Silicon-Labs USB device. If no PC  is available,  the system can be configured entirely through it’s web interface, a prescribed  procedure needs to be followed  and requires you to temporarily set the SSID and encryption of your router to the default values of the station to be configured.

For system board I-O pin description and location see here.

For an overview of interconnect  and cabling options see here.

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