Nuckeo-F446REで出力PWMの周波数を変える方法 How to change freq. of PWM in using Nuckeo-F446RE

日本語フォーラム / Japanese Forum
1

Nuckeo-F446REでタイマー割込みを使ってPWM波を周波数を変えて自由に出したいと思い、TIM2でタイマカウンタのアップ・ダウンとルックアップデータを比較してPWM波を出そうとしましたが、レジスタ(TIM2->CR1)を変えてものこぎり波のような変化をしてしまいうまくいきません。
TIM2はmbed側での予約タイマでタイマカウントの方法は変えられないのでしょうか？もしその場合別のタイマーを使うべきなのでしょうか？
ちなみにkeil studioのディレクトリも見ましたが、予約タイマを設定しているプログラム等は見つかりませんでした。
(念のため英語でも書きます)

English:
I want to make a PWM wave with variable frequency by timer interrupt of Nuckeo-F446RE.
I tried to make those by comparing Look up data with timer counter. But even though I change register CR1 of TIM2(TIM2->CR1), timer counter keeps the up counter modeーI couldn’t change register in itself.
Is timer TIM2 is reserved by mbed(Can’t I change the timerTIM2)? And do I have to use another timer?
As a side note, I searched keil studio’s directories for TIM2 setting program, but I couldn’t find it.

2

Hello,

Mbed used TIM5 for STM32F4 family

BR, Jan

3

Hello.

Thank you for replying.

Mbed uses TIM5―We cannot change TIM5 register. OK.
Then, TIM2 can be changed, but I can’t (The output wave shows upcount movement).
I use this in source code: TIM2->CR1 |= 0b1100000;
CR1 is TIMx control register(Of course, TIM2 is included), and bit 5 and 6 are PWM mode changers:
“00” is only up or down counter.
“01”,"10 ",“11” are both up and down counters. Difference of those is as follows:
“01” loads the target number when counter counts 0(down).
"10 "loads the target number when counter counts TIM2->ARR(up).
“11” loads the target number when counter counts both 0 and TIM2->ARR(up and down).

Other registers are as follows:
RCC->APB1ENR |= 0x1;
TIM2->CR1 |= 0b0001010000;
TIM2->PSC = 100-1;
TIM2->ARR = 1000;
TIM2->CCMR1 = 0x6868;
TIM2->CCMR2 = 0x0068;
and TIM2->CCR1~3( for target of counter).

Do I have to set other registers?

4

For the correct workflow with registers you have to check reference manual for your MCU. Or you can do it with HALs.

BR, Jan