Step 4: Enabling Peripherals and Creating an STM32 Pin Out
Main window, Pinout tab, with no pins assigned
Click to enlarge
The Pinout tab is used to select and assign pins to the peripherals available
on the selected STM32 ARM Cortex-M MCU, and select from the available middleware
The right pane of the Pinout tab displays an image of the selected STM32 ARM Cortex-M MCU. In
this example a BGA part was selected, so the image shows all the pins on
the BGA part. The main graphic at the top right of this page shows how the
Pinout tab looks when an LQFP part number is selected. Hovering
the mouse over a pin displays the possible assignments for that pin.
If the project was created by selecting an STM32 ARM Cortex-M part number and package
then no pins will yet be assigned.
If the project was created by selecting an STM32 evaluation board (eval,
STM32 Nucleo, etc.) then the pins will already be assigned to be correct for
the selected hardware.
The top of the left pane of the pinout tab displays the middleware available
for use on the selected part. The bottom of the left pane of the pinout
tab displays the drivers available for use on the selected part.
Note that, by default, FreeRTOS is already available for selection (it is not
greyed out), but lwIP (the TCP/IP stack) is not available for selection (it is greyed
out). This is because, by default, none of the peripherals are yet
enabled, and the STM32CubeMX software knows that lwIP cannot be selected
unless the Ethernet peripheral has first been enabled. The work flow
steps below demonstrate how to enable peripherals, including the Ethernet
hardware, and the effect of doing so on the availability of pins and other
In the left pane of the Pinout tab, locate and expand the
ETH peripheral in the list of available IPs. By default it
is set to "Disable".
Experiment changing the ETH peripheral from "Disable" to
"RMII" then "MII". While doing this note:
The effect on the pin assignment display in the right pane.
STM32CubeMX searches for the pinout configuration that best
suites the set of selected peripherals. Pin assignments can be
fixed by checking the "Keep Current Signal Placement"
check box, which is located in the menu bar. Pin assignments can
also be made manually by clicking on a pin in the
right pane, then selecting an assignment for that pin
from the drop down list (this latter method is only
recommended for advanced users).
lwIP automatically becomes available for selection
when the ETH peripheral is enabled.
Exclamation marks appear on the ADC1, ADC2 and ADC3 peripherals. The
exclamation marks highlight potential pin assignment conflicts that the tool cannot
Next expand the ADC1 peripheral. Note the pins that are no
longer available to the ADC because the ETH peripheral has
been enabled are marked in red.
Check a box to assign an input to the ADC. It is not possible
to assign an input that clashes with the ETH peripheral.
Continue selecting peripheral and middleware components until
your design requirements have been met.
Finally - unused pins can be set on-mass to GPIO outputs by
selecting "Set unused GPIOs" from the STM32CubeMX "Pinout" menu.
On to step five
Back to the STM32CubeMX practical walk-through index
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