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Add a new variant (board)

What is a variant?

It is described by Arduino here

A core variant folder is an additional folder that is compiled together with the core and allows platform developers to easily add specific configurations.

Variants must be placed inside the variants folder in the current architecture.

Note

Since STM32 core release 2.0.0 the variants folder contains one folder for each STM32 MCU family.

Tip

The example of all the steps below is available in PR #1398.

Variants folders 
variants/
|-- STM32C0xx/
|-- STM32C5xx/
|-- STM32F0xx/
|-- STM32F1xx/
|-- STM32F2xx/
|-- STM32F3xx/
|-- STM32F4xx/
|-- STM32F7xx/
|-- STM32G0xx/
|-- STM32G4xx/
|-- STM32H5xx/
|-- STM32H7xx/
|-- STM32L0xx/
|-- STM32L1xx/
|-- STM32L4xx/
|-- STM32L5xx/
|-- STM32MP1xx/
|-- STM32U0xx/
|-- STM32U3xx/
|-- STM32U5xx/
|-- STM32WB0x/
|-- STM32WBAxx/
|-- STM32WBxx/
|-- STM32WL3x/
`-- STM32WLxx/

Each MCU family has several MCU references. Each subfolder name can contain one or more mcu reference(s).

STM32G0xx family example 
STM32G0xx/
|-- G030C(6-8)T/
|-- G030F6P/
|-- G030J6M/
|-- G030K(6-8)T/
|-- G031C(4-6-8)(T-U)_G041C(6-8)(T-U)/
|-- G031F(4-6-8)P_G031Y8Y_G041F(6-8)P_G041Y8Y/
|-- G031G(4-6-8)U_G041G(6-8)U/
|-- G031J(4-6)M_G041J6M/
|-- G031K(4-6-8)(T-U)_G041K(6-8)(T-U)/
|-- G050C(6-8)T/
|-- G050F6P/
|-- G050K(6-8)T/
|-- G051C(6-8)(T-U)_G061C(6-8)(T-U)/
|-- G051F6P_G051F8(P-Y)_G061F6P_G061F8(P-Y)/
|-- G051G(6-8)U_G061G(6-8)U/
|-- G051K(6-8)(T-U)_G061K(6-8)(T-U)/
|-- G070CBT/
|-- G070KBT/
|-- G070RBT/
|-- G071C(6-8-B)(T-U)_G081CB(T-U)/
|-- G071EBY_G081EBY/
|-- G071G(6-8-B)U_G081GBU/
|-- G071G(8-B)UxN_G081GBUxN/
|-- G071K(6-8-B)(T-U)_G081KB(T-U)/
|-- G071K(8-B)(T-U)xN_G081KB(T-U)xN/
|-- G071R(6-8)T_G071RB(I-T)_G081RB(I-T)/
|-- G0B0CET/
|-- G0B0KET/
|-- G0B0RET/
|-- G0B0VET/
|-- G0B1C(B-C-E)(T-U)_G0C1C(C-E)(T-U)/
|-- G0B1C(B-C-E)(T-U)xN_G0C1C(C-E)(T-U)xN/
|-- G0B1K(B-C-E)(T-U)_G0C1K(C-E)(T-U)/
|-- G0B1K(B-C-E)(T-U)xN_G0C1K(C-E)(T-U)xN/
|-- G0B1M(B-C-E)T_G0C1M(C-E)T/
|-- G0B1NEY_G0C1NEY/
|-- G0B1R(B-C-E)(I-T)xN_G0C1R(C-E)(I-T)xN/
|-- G0B1R(B-C-E)T_G0C1R(C-E)T/
`-- G0B1V(B-C-E)(I-T)_G0C1V(C-E)(I-T)/

MCU name are factorized to avoid long path names, for example:

G0B1R(B-C-E)T_G0C1R(C-E)T is for G0B1RBT, G0B1RCT, G0B1RET, G0C1RCT and G0C1RET.

All generic variants are now automatically generated in the variant folder thanks the STM32_open_pin_data repository which provides all the information required for the pin configuration of products based on STM32 MCU.

This means that the generic STM32 MCU files required for a variant are generated inside each MCU folder. Only the linker script is not automatically generated. Note that the default system clock configuration is empty by default. So the default clock at reset will be used.

Generated variant files

Warning

Below files are automatically generated so do not modify them. Only the generic_clock.c can be modified to add default system clock configuration and so will not be overwritten.

  • board_entry.txt: contains generic variant declaration to ease board addition in the boards.txt file. See Arduino boards.txt specification.
  • generic_clock.c: contains the default system clock configuration: WEAK void SystemClock_Config(void)
  • PinNamesVar.h: contains specific PinName definitions of the MCU
  • PeripheralPins.c: contains list of available PinName per peripheral.
  • variant_generic.cpp: contains Digital PinName array and Analog (Ax) pin number array
  • variant_generic.h: contains all definition required by the variant: STM32 pin number definitions, peripheral pins for default instances: Serial, I2C, SPI, Tone, Servo, ...

Use the dedicated workflows from the submenu:

Tip

If you have any issue with the following guide. Do not hesitate to ask question on the stm32duino Github discussions or the stm32duino forum.