How to implement the missing CC channels and interrupts in low layer API?

[Michael B.]

Hi

I just started porting a project over to STM32. It does some complex stuff with timers. First I found out the the HAL doesn't support my usage of one pulse mode in timers. So I went for the LL API which I liked on first sight.

Now I found out that the LL API only implements 4 of 6 capture compare channels of the advanced timer 1 of STM32F3xx.

I need at least 5 CC channels. What can I do to get the rest of the CC channels?

I started adding the missing functions and constants but I suppose I won't get it to run because I also need the corresponding interrupts and other functionality so I will probalby hit something not implemented in C.

Best Regards

Michael Bürschgens

[waclawek.jan]

> I will probalby hit something not implemented in C

You mean, something not implemented in the Cube/LL "library"?

For anything more complex than the basic functionality, it's probably better to avoid any "library" and program directly at the register level. Simply read the TIM1 chapter in RM and follow the registers descriptions.

JW

[waclawek.jan]

You did not tell us exactly which STM32F3xx you use, so I just looked at the TIM1/TIM8/TIM20 chapter of RM0316 Rev.8, and noticed, that there are no *interrupt enable flags* for channels 5 and 6 mentioned in TIMx_DIER , although there are respective *interrupt flags* in TIMx_SR (CC5IF and CC6IF).

I don't have a 'F3xx at hand to try now, but it may as well mean that these channels can't trigger an interrupt.

JW

[Michael B.]

The MCU is STM32F302x8 but the *_ll_tim.h is the same for all. The datasheet mentiones the timers and their registers.

[Michael B.]

With "not implemented in C" I mean that maybe some necessary calls are not implemented in the binding layer between compiled code and hardware. I don't know the right terminology. I mean what the linker links to.

[Michael B.]

You are right. There are some registers missing. So the last two CC channels are almost useless. What a pitty. :(

[Jeroen3]

"not implemented in the binding layer between compiled code and hardware"

I think you do not understand the concept of bare metal embedded programming. The timer is just a block of registers on the memory map. You can access these via a pointer and an operation with the correct width. That is a limit of the hardware.

Only complex operating where the ARM Cortex does not have instructions for will the linker map to a library. Floating points for example. Reading and writing timer register is not one of those.

Take a look inside the hal or hal_ll to see there is no "binding layer".

I don't think there are any language features of C unavailable, C++ however...

[Imen.D · Accepted solution]

 Hello,

The channel 5 and 6 do not have an interruption or DMA request.

 

 And about the status register TIMx_SR, the bit of this register is set when the counter matches the corresponding compare value even if the interruption is disabled.

Best Regards,

Imen.

[waclawek.jan]

Thanks for the clarification, Imen.

It's a pity they don't. I also don't get the purpose of OC6 (i.e. the output control unit of channel 6), and in TIM20, also OC5...

JW