Step 4: Enabling Peripherals and Creating an STM32 Pin Out

Main window, Pinout tab, with no pins assigned
Click to enlarge

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 peripherals.

Workflow steps:

1. 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".

2. Experiment changing the ETH peripheral from "Disable" to "RMII" then "MII". While doing this note:
   1. 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).

   2. lwIP automatically becomes available for selection when the ETH peripheral is enabled.

   3. Exclamation marks appear on the ADC1, ADC2 and ADC3 peripherals. The exclamation marks highlight potential pin assignment conflicts that the tool cannot resolve automatically.

3. 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.

4. Check a box to assign an input to the ADC. It is not possible to assign an input that clashes with the ETH peripheral.

5. Continue selecting peripheral and middleware components until your design requirements have been met.

6. Finally - unused pins can be set on-mass to GPIO outputs by selecting "Set unused GPIOs" from the STM32CubeMX "Pinout" menu.

Click images to enlarge
Configuring ETH for MII	ADC input options after ETH selection	Manually assigning a pin from a drop down list	The view after all unused pins are set to GPIO

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