The CMSIS-Driver specification is a software API that describes peripheral driver interfaces for middleware stacks and user applications. The CMSIS-Driver API is designed to be generic and independent of a specific RTOS making it reusable across a wide range of supported microcontroller devices. The CMSIS-Driver API covers a wide range of use cases for the supported peripheral types, but can not take every potential use-case into account. Over time, it is indented to extend the CMSIS-Driver API with further groups to cover new use-cases.

The CMSIS Software Pack publishes the API Interface under the Component Class CMSIS Driver with header files and a documentation. These header files are the reference for the implementation of the standardized peripheral driver interfaces. These implementations are published typically in the Device Family Pack of a related microcontroller family under the Component Class CMSIS Driver. A Device Family Pack may contain additional interfaces in the Component Class Device to extend the standard Peripheral Drivers covered by this CMSIS-Driver specification with additional device specific interfaces for example for Memory BUS, GPIO, or DMA.

The standard peripheral driver interfaces connect microcontroller peripherals for example with middleware that implements communication stacks, file systems, or graphic user interfaces. Each peripheral driver interface may provide multiple instances reflecting the multiple physical interfaces of the same type in a device. For example the two physical SPI interfaces are reflected with a separate Access Struct for SPI1 and SPI2. The Access Struct is the interface of a driver to the middleware component or the user application.

Peripheral Driver Interfaces and Middleware

The following CMSIS-Driver API groups are defined:

CAN: Interface to CAN bus peripheral.
Ethernet: Interface to Ethernet MAC and PHY peripheral.
I2C: Multi-master Serial Single-Ended Bus interface driver.
MCI: Memory Card Interface for SD/MMC memory.
NAND: NAND Flash Memory interface driver.
Flash: Flash Memory interface driver.
SAI: Serial audio interface driver (I2s, PCM, AC'97, TDM, MSB/LSB Justified).
SPI: Serial Peripheral Interface Bus driver.
Storage: Storage device interface driver.
USART: Universal Synchronous and Asynchronous Receiver/Transmitter interface driver.
USB: Interface driver for USB Host and USB Device communication.
VIO: API for virtual I/Os (VIO).
WiFi: Interface driver for wireless communication.

Note: Usually, WiFi chips and modules have their own networking stack incorporated. This means that payload data is sent via a serial interface (SPI or USART) to the WiFi chip/module and the Ethernet frames are assembled inside. If you intend to use a TCP/IP stack from a middleware component with a WiFi chip/module, make sure that the WiFi driver has a WiFi Bypass Mode. This allows to send the Ethernet frames assembled by the TCP/IP component transparently through the WiFi chip/module.

CMSIS-Driver in ARM::CMSIS Pack

The following files relevant to CMSIS-Driver are present in the ARM::CMSIS Pack directories:

Directory	Content
CMSIS/Documentation/Driver	This documentation
CMSIS/Driver/Include	Driver header files (Driver_interface.h, Driver_Common.h)
CMSIS/Driver/DriverTemplates	Driver implementation template files (Driver_interface.c)