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USER MANUAL FOR HARDWARE REV 3.11
07-APR-2018
PAGE 11
3.11
UART HEADER
The UART interface from the Raspberry PI has
been brought out to a switch that allows the user
to select to use the UART for either a terminal or
other serial device, or, to use the UART interface
to receive data from the optional GPS board.
The signal levels on this connection are all 3.3V logic, and Zener diodes have
been included to help protect the devices, but are intended to protect
against transient voltage spikes resulting from mating connectors or similar. These will not protect
again improper voltages applied to the pins.
3.12
PI STACKING HEADER
As it has been anticipated that users may wish to design custom
daughter boards, the primary 40 pin header has been left
exposed so the user may design standard form-factor boards.
It is important to remember that the majority of the native
GPIO pins have already been utilized and these pins must be
left unconnected in any custom designed daughter boards.
The illustration at the right shows the availability of each of the
pins on the 2x20 header, along with shared bus pins that must
be used as configured for the system to maintain functionality.
Signals such as the I2C, SPI, 1-wire, etc. are broken out into
dedicated headers that may or may not be simpler to design around, this is left to the user to decide. It
is critical to remember that the signals on this connecter are 3.3V logic, and 5V logic levels can damage
your devices.
