libopencm3
A free/libre/open-source firmware library for various ARM Cortex-M3 microcontrollers.
STM32G4
Here is a list of all modules:
[detail level 1234]
 CM3 DefinesDefined Constants and Types for Cortex M3 core features
 DebuggingMacros and functions to aid in debugging
 Cortex Core Defineslibopencm3 Defined Constants and Types for the Cortex Core
 Cortex-M Data Watch and Trace unit.System Control Space (SCS) => Data Watchpoint and Trace (DWT)
 Cortex-M Flash Patch and Breakpoint (FPB) unit
 Cortex-M Instrumentation Trace Macrocell (ITM)
 Cortex-M MPU Defineslibopencm3 Cortex Memory Protection Unit
 Cortex-M NVIC Defineslibopencm3 Cortex Nested Vectored Interrupt Controller
 Cortex-M System Control BlockThe System Control Block is a section of the System Control Space
 Cortex-M System Control SpaceThe System Control Space (SCS) is a memory-mapped 4KB address space that provides 32-bit registers for configuration, status reporting and control
 Cortex-M SysTick Defineslibopencm3 Defined Constants and Types for the Cortex SysTick
 Cortex-M Trace Port Interface Unit (TPIU)
 Cortex Core Peripheral APIsAPIs for Cortex Core peripherals
 DWTlibopencm3 Cortex-M Data Watchpoint and Trace unit
 NVIClibopencm3 Cortex Nested Vectored Interrupt Controller
 SCBlibopencm3 Cortex-M System Control Block
 SysTicklibopencm3 Cortex System Tick Timer
 Coresight RegistersCoreSight Lock Status Registers and Lock Access Registers are documented for the DWT, ITM, FPB and TPIU peripherals
 Peripheral APIsAPIs for device peripherals
 QuadSPI peripheral APIAPIs for the specialized SPI Flash peripheral
 DMA peripheral APIDMA library for the multi channel controller found in F0/1/3 & L/G parts
 FLASH peripheral APIlibopencm3 STM32G4xx FLASH
 PWR peripheral APIlibopencm3 STM32G4xx Power Control
 RCC peripheral APIlibopencm3 STM32G4xx Reset and Clock Control
 ADC peripheral APIlibopencm3 STM32G4xx ADC
 CORDIC peripheral APIHW accelerated maths trig/hyperbolic operations
 CRC peripheral API
 CRS peripheral API(USB) STM32 Clock Recovery Subsystem
 DAC peripheral APIDigital to Analog Converter
 DMAMUX peripheral API
 GPIO peripheral API
 I2C peripheral API
 OPAMP peripheral API
 RNG peripheral APIThis library supports "version 1" of the random number generator peripheral (RNG) in the STM32 series of ARM Cortex Microcontrollers by ST Microelectronics
 SPI peripheral API
 TIMER peripheral API
 USART peripheral API
 FDCAN peripheral APIlibopencm3 STM32 FDCAN
 STM32G4xxLibraries for ST Microelectronics STM32G4xx series
 STM32G4xx DefinesDefined Constants and Types for the STM32G4xx series
 ADC DefinesDefined Constants and Types for the STM32G4xx Analog to Digital converter
 CORDIC DefinesDefined Constants and Types for the STM32G4xx CORDIC
 CRC DefinesDefined Constants and Types for the STM32G4xx CRC Generator
 CRS DefinesDefined Constants and Types for the Clock Recovery System
 DAC DefinesDefined Constants and Types for the STM32G4xx DAC
 DMA DefinesDefined Constants and Types for the STM32G4xx DMA Controller
 DMAMUX DefinesDefined Constants and Types for the STM32G4xx DMAMUX
 FDCAN Defines
 FLASH DefinesDefined Constants and Types for the STM32G4xx Flash Control
 GPIO DefinesDefined Constants and Types for the STM32G4xx General Purpose I/O
 I2C DefinesDefined Constants and Types for the STM32G4xx I2C
 OPAMP Defineslibopencm3 Defined Constants and Types for the STM32G4xx Operational Amplifier module
 PWR DefinesDefined Constants and Types for the STM32G4xx Power Control
 QuadSPI DefinesDefined constants and types for the STM32G4 QuadSPI peripheral
 RCC DefinesDefined Constants and Types for the STM32G4xx Reset and Clock Control
 RNG DefinesDefined Constants and Types for the STM32G4xx RNG Control
 SPI DefinesDefined Constants and Types for the STM32G4xx SPI
 SYSCFG DefinesDefined Constants and Types for the STM32G4xx Sysconfig
 Timer DefinesDefined Constants and Types for the STM32G4xx Timers
 USART DefinesDefined Constants and Types for the STM32G4xx USART
 User interrupt service routines (ISR) prototypes for STM32 G4 series
 USB DefinesDefined Constants and Types for the STM32F* USB drivers
 USB Audio Type DefinitionsDefined Constants and Types for the USB Audio Type Definitions
 USB CDC Type DefinitionsDefined Constants and Types for the USB CDC Type Definitions
 USB HID Type DefinitionsDefined Constants and Types for the USB HID Type Definitions
 USB MSC Type DefinitionsDefined Constants and Types for the USB MSC Type Definitions
 USB DriversDefined Constants and Types for the USB Drivers
 USB Standard Structure DefinitionsDefined Constants and Types for the USB Standard Structure Definitions
 User interrupt service routines (ISR) defaults for STM32 G4 series
 Generic USB DriversGeneric USB Drivers
 Generic USB Control RequestsGeneric USB Control Requests
 Generic USB Standard Request InterfaceGeneric USB Standard Request Interface
 Usb_msc