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stm32: hard pwm allow scale PWM frequency

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To support the cartographer, it is required to output 24 MHz.
With current defaults max output frequency is:
48 MHz/256 = 187.5 KHz
Adjusting the PWM scale allows for ramping up the frequency.

To not mess up with existing PWM users,
define the STM32-specific command.

Signed-off-by: Timofey Titovets <nefelim4ag@gmail.com>
This commit is contained in:
Timofey Titovets 2025-10-15 04:25:43 +02:00 • committed by KevinOConnor
parent 12cc944fa0
commit ec0eb4a8bf
1 changed files with 31 additions and 3 deletions
Download patch file Download diff file Expand all files Collapse all files

34
src/stm32/hard_pwm.c
View file

@ -300,7 +300,8 @@ static const struct gpio_pwm_info pwm_regs[] = {
};
struct gpio_pwm
gpio_pwm_setup(uint8_t pin, uint32_t cycle_time, uint32_t val)
gpio_timer_setup(uint8_t pin, uint32_t cycle_time, uint32_t val,
int is_clock_out)
{
// Find pin in pwm_regs table
const struct gpio_pwm_info* p = pwm_regs;
@ -316,7 +317,18 @@ gpio_pwm_setup(uint8_t pin, uint32_t cycle_time, uint32_t val)
uint32_t pclock_div = CONFIG_CLOCK_FREQ / pclk;
if (pclock_div > 1)
pclock_div /= 2; // Timers run at twice the normal pclock frequency
uint32_t prescaler = cycle_time / (pclock_div * (MAX_PWM - 1));
uint32_t max_pwm = MAX_PWM;
uint32_t pcycle_time = cycle_time / pclock_div;
uint32_t prescaler = pcycle_time / (max_pwm - 1);
// CLK output
if (is_clock_out) {
prescaler = 1;
while (pcycle_time > UINT16_MAX) {
prescaler = prescaler * 2;
pcycle_time /= 2;
}
max_pwm = pcycle_time;
}
if (prescaler > UINT16_MAX) {
prescaler = UINT16_MAX;
} else if (prescaler > 0) {
@ -334,9 +346,12 @@ gpio_pwm_setup(uint8_t pin, uint32_t cycle_time, uint32_t val)
if (p->timer->PSC != (uint16_t) prescaler) {
shutdown("PWM already programmed at different speed");
}
if (p->timer->ARR != (uint16_t) max_pwm - 1) {
shutdown("PWM already programmed with different pulse duration");
}
} else {
p->timer->PSC = (uint16_t) prescaler;
p->timer->ARR = MAX_PWM - 1;
p->timer->ARR = max_pwm - 1;
p->timer->EGR |= TIM_EGR_UG;
}
@ -393,6 +408,19 @@ gpio_pwm_setup(uint8_t pin, uint32_t cycle_time, uint32_t val)
return channel;
}
struct gpio_pwm
gpio_pwm_setup(uint8_t pin, uint32_t cycle_time, uint32_t val) {
return gpio_timer_setup(pin, cycle_time, val, 0);
}
void
command_stm32_timer_output(uint32_t *args)
{
gpio_timer_setup(args[0], args[1], args[2], 1);
}
DECL_COMMAND(command_stm32_timer_output,
"stm32_timer_output pin=%u cycle_ticks=%u on_ticks=%hu");
void
gpio_pwm_write(struct gpio_pwm g, uint32_t val) {
*(volatile uint32_t*) g.reg = val;