How to use
- Copy the installation command and review the source package before installing it in your own agent environment.
- Check the source document for required tools, credentials and supported hosts.
- Describe your input and desired deliverable; review the output against the source material.
npx skills add https://github.com/mohitmishra786/low-level-dev-skills --skill timers-pwm-baremetalBefore you start
- Installation does not include a model subscription, API allowance or permission to access your files.
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Original skill document
Rendered from the source repository. Headings, examples, code, tables, links, and referenced images are preserved.
Timers and PWM (Bare-Metal)
Purpose
Configure MCU timers for PWM output, input capture, and periodic scheduling: prescaler/ARR setup, compare channels, and SysTick as a simple tick source.
When to Use
- Motor/LED dimming via PWM
- Measuring pulse width (input capture)
- Bare-metal
millis()without FreeRTOS - Hardware periodic sampling trigger
Workflow
1. PWM on TIM2 CH1 (STM32)
f_pwm = f_timer_clk / ((PSC+1) * (ARR+1))
duty = (CCR / (ARR+1)) * 100%c
RCC->APB1ENR |= RCC_APB1ENR_TIM2EN;
TIM2->PSC = 83; /* 84MHz / 84 = 1 MHz tick */
TIM2->ARR = 999; /* 1 kHz PWM */
TIM2->CCR1 = 500; /* 50% duty */
TIM2->CCMR1 |= (6U << TIM_CCMR1_OC1M_Pos); /* PWM mode 1 */
TIM2->CCER |= TIM_CCER_CC1E;
TIM2->CR1 |= TIM_CR1_CEN;GPIO: PA0 AF1 TIM2_CH1.
2. SysTick tick
c
volatile uint32_t tick_ms;
void SysTick_Handler(void) {
tick_ms++;
}
void systick_init(uint32_t hz) {
SysTick_Config(SystemCoreClock / hz);
}3. Input capture
Configure channel in CCMR as input, set CCER polarity, read CCR on interrupt when edge captured.
4. Agent usage
/timers-pwm-baremetal 1 kHz 25% duty PWM on TIM2 channel 1Common Problems
| Symptom | Cause | Fix |
|---|---|---|
| Wrong frequency | APB timer clock doubling | Check RM timer clock x2 rule |
| No PWM output | CCER/CCMR not enabled | Enable channel output |
| Jittery tick | SysTick overridden | One owner for SysTick |
Related Skills
skills/baremetal/gpio-baremetal— timer pin AFskills/embedded/freertos— replace SysTick with RTOS tickskills/baremetal/adc-dac-baremetal— timer TRGO for ADC trigger
