====== Special features ======
original source(([[http://en.blitzortung.org/Compendium/Documentations/Documentation_2014-05-11_Red_PCB_10.4_PCB_12.3_PCB_13.1_PCB_14.1.pdf|Documentation System RED]], chapter 5.6))

FIXME Mark the sections for RED/BLUE only.

FIXME If there are BLUE only sections, add them.

===== Actions and Alerts =====

Lightning alerts can warn you with different actions (i.e. sounds) about approaching thunderstorms.
This feature is available since firmware version 6.0.

The **alerts** are based on the TOA lightning data from our servers. You can specify your desired
parameters like minimum distance, stroke count and time period. These values will be checked by our
servers by the remote configuration feature. If the alert conditions are true, then a desired action will
be issued.

An action can be triggered by a lightning alert or by other events (see next sections). The action
defines which alarm sound should be played or whether an output pin should be enabled. A user
defined URL can be called, which can be used for own purposes. After an action has been issued, it
can be ignored for a adjustable time. An action can also be used by different events.

<note important>Do not use these lightning alerts as the only source for protection of life or property! We can not
guarantee for availability and quality of this feature! The alerts are not available when in "Monitor
Mode".</note>

==== AS3935 Franklin Lightning Sensor ====

The AS3935 is a new microchip from austriamicrosystems, which has some lightning detection technique
inside. It has been designed for mobile devices, which can inform their users about regional
lightning activity. The signals from lightning strokes are received by a tiny ferrite antenna, which is
tuned to 500 kHz. Compared with our own powerful amplifier/controller combination, the AS3935 is
very simple and cheap, but it can not be used for lightning locating. Complete PCBs with microchip
and antenna are available from different distributors.

The AS3935 can be connected to our controller board via I2C bus with 5 wires. Almost every
parameter can be adjusted in the web-interface. The calibration of the antenna is done automatically
after boot and after each parameter change. Refer to the AS3935 datasheet for more information about
the parameters. When the AS3935 detects lightning, different actions can be started, depending on
lightning count and distance (see [[en:hardware:firmware:special_features#actions_and_alerts|]]).

<note important>This feature is for experts only! Do not use the AS3935 lightning alert as the only source for
protection of life or property!</note>

==== User I/Os ====

Some pins of the STM32F4-MCU can be used as user defined inputs or outputs.

If defined as an input, a rising and/or falling edge (configurable) can trigger an action (see 5.6.1).
Additionally, an URL can be called. This URL will contain parameters with the time-stamp of the
trigger derived from the GPS 1PPS timer. Thus, it is possible to use the inputs for high-precision
timing measurements.

Outputs are configured in push-pull mode. Each output can drive currents up to 20mA. The
summarized current of all outputs shouldn’t exceed 50mA. Please check the STM32F407 datasheet
for more information! An output can be toggled by calling a dedicated URL of the web-interface.
Outputs can also be triggered by actions (see 5.6.1). As an example, it is possible to let a LED blink
on a lightning alerts.

<note important>This feature is for experts only! Be careful on changing settings and/or modifying your hardware!
Never connect switches/buttons without series resistors to the ports! Otherwise short-circuits
could destroy the MCU!</note>

==== Analogue user input ====

The analogue user input is an optional feature, which has nothing to do with lightning detection. When
enabled, you can measure DC voltages from -3 to 30V at the measuring point. You will see them
on the web-interface below CPU temperature and on the LCD on the first page. The voltage range
can be changed by replacing resistors R64 and R65 with other values. You also have to change those
values in the settings section on the web-interface. The default values are 10kΩ for the serial resistor
Rs (R65) and 1kΩ for the RGND (R64). If you enter 0 for the RGND, then original voltage on the
ADC-input pin will be shown.

Please note, that only voltages with low impedance can be measured, i.e. voltages from a powersupply
or from a battery. The STM32F4DISCOVERY has an additional 10k
 pull-up to 3V included,
which cannot be changed. As the used CPU-pin is also dedicated for a special function on the
STM32F4DISCOVERY, a green LED will light up there when low voltages are applied.

<note important>Use this feature at your own risk! Wrong resistor values and/or too high voltages can damage your
system!</note>