istiaq2379 istiaq2379 - 2 months ago 19
C Question

CMSIS and peripherals drivers

what types of codes are written in CMSIS files and peripheral drivers file. How can I distinguish them? any example would be more helpful. Thank you.

Answer

"CMSIS" is the Cortex Microcontroller Software Interface Standard. It's an ARM standard, so the code should be more or less portable between Cortex implementations.

Peripheral libraries generally are more vendor-specific, since there's no standard for how two different vendors will implement e.g. a timer or a UART block.

At least, that's my basic understanding from working (mostly) with ARMs in the STM32 family. However, I notice on that CMSIS page that the scope for CMSIS is actually larger:

CMSIS-Driver: defines generic peripheral driver interfaces for middleware making it reusable across supported devices. The API is RTOS independent and connects microcontroller peripherals with middleware that implements for example communication stacks, file systems, or graphic user interfaces.

That sounds like it'd do things that I associate with vendor-specific code, but perhaps not all vendors actually use CMSIS-Driver yet.

UPDATE: On the STM32:s I've worked with, GPIO is managed using only ST's peripheral library.

It's pretty easy, really:

  1. Use RCC_AHB1PeriphClockCmd() to enable the GPIO peripheral's clock. There are many clocks so make sure you do it right. I think all the GPIO is on AHB1.
  2. Initialize a variable of type GPIO_InitTypeDef by calling GPIO_StructInit() on it to get the defaults.
  3. Set the settings you really want in your GPIO_InitTypeDef, overriding the defaults as needed.
  4. Call GPIO_Init() on the proper port, also passing it the GPIO_InitTypeDef with your actual settings. This will poke registers in the peripheral.
  5. Use calls like GPIO_SetBits(), GPIO_ReadInputDataBit() et cetera to actually use the GPIO pin.