User's Manual

 37
Programming Considerations
GPIO pin use table
GPIO Pin Use
Name
Register
Bit
Category
External
Interface
Description
TXSD/
SPI_TX/
GPIO-6
GPIO[7] Allocated
Pin 4 on the
main header
Used for the serial TXD or SPI_TX, but
could be reassigned as a GPIO, timer out 7 or
in 8.
If used with the development board, this pin
maps to GPIO-6.
DTR/GPIO-
5
GPIO[6] Allocated
Pin 6 on the
main header
Usedc for the serial DTR but could be
reassigned as a GPIO, or timer in 7.
If used with the development board, this pin
maps to GPIO-5.
RTS/
SPI_CLK/
GPIO-4 (See
description)
GPIO[5]or
GPIO[4]
Allocated
Pin 5 on the
main header
Since these two processor pins map to the
same header pin, one must
be configured as
an input to avoid contention.
UART: GPIO[5] is confiured for RTS and
GPIO[4] for GPIO input.
SPI: GPIO[5] for GPIO input and GPIO[4]
for SPI_CLK.
Other: GPIO[5] supports IRQ3 and timer out
6.
GPIO[4] supports IRQ2 and timer in 6.
If used with the development board, header
pin 5 maps to GPIO-4.
RXD/
SPI_RX/
GPIO-7
GPIO[3] Allocated
Pin 3 on the
main header
Used for the serial RXD or SPI_RX, but
could be reassigned as a GPIO or PICO-3.
If used with the development board, this pin
maps to GPIO-7.
DSR/GPIO-
3
GPIO[2] Allocated
Pin 9 on the
main header
Used for the serial DSR, but could be
reassigned as a GPIO or PICO-2.
If used with the development board, this pin
maps to GPIO-3.