Datasheet

3.1 The console serial line
Of particular interest on the ATmega128L MCU are the pins used for serial line commu-
nication (pins 2, 3 and GND) as well as the SPI
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lines.
Pins 2, 3 and GND are routed directly to the expansion connector at the rear of the
console. The signal logic adheres to the EIA-232 (RS-232) specification, though signal
levels are 3.3V only. As such, a level converter is required for interfacing to a personal
computer, which would otherwise fry the MCU. A number of small computer systems
such as the Raspberry Pi [13] expose a 3.3V serial line, meaning that a direct connection
to the serial line on the Davis console is possible. A level converter may still be required,
refer to the parts list in section 6.1 for details.
The availability of a console serial line is a well-known fact, used by third-party software
and pheripheral equipment developers. Although official Davis documentation states that a
data logger unit is required, it turns out it is not a requirement to access the serial line.
A variety of applications have been developed by users having a desire to add func-
tionality to their consoles: data loggers, interface units, XBee and Bluetooth modules for
wireless data retrieval — just to mention the more common ones. A common denomi-
nator is that users want to expand the capabilities of their units, using long-established,
well-known and well-documented features offered by their Vantage Pro2 consoles. This
expandability indicates a good initial design of the console unit, and it is a shame to see
it go only due to poor management decisions at the Davis HQ.
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Serial Pheripheral Interface.
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