PWM Device

GPTim (General Purpose Timer), LPTim (Low Power Timer), and ATIM (Advanced Timer) can work in PWM mode for hardware timers:

• General Purpose Timer (GPTim): GPTim implements a 16-bit counter for system PCLK, providing 1-65536 prescaler. It has 4 input/output channels. GPTim can be used for PWM to generate waveform signals or measure input signals.

• Low Power Timer (LPTim): LPTim implements a 16-bit counter for system PCLK or low power clock, providing 1-128 prescaler. LPTim can be used for PWM to generate waveform signals.

• Advanced Timer (ATIM): ATIM implements a 32-bit counter for system PCLK, providing 1-65536 prescaler. It has 6 channels, channels 1-3 can be configured as input or output mode respectively, where each channel can output two complementary PWM signals with dead-time protection, channel 4 can be configured as input or output mode and can output single PWM, channels 5-6 can be configured as output compare mode.

Hardware PWM driver includes two layers: hardware access layer (HAL) and RT-Thread adaptation layer.
HAL provides basic APIs for accessing hardware timer peripheral registers. For details, please refer to the API documentation of hardware timer HAL.
The adaptation layer provides support for RT-Thread driver framework. Users can use RT-Thread POSIX driver interface for PWM programming. Device names like pwm3, pwm4, pwmlp1, and pwmlp3 are configured in menuconfig.

Driver Configuration

Select the PWM devices to use in the On-Chip Peripheral RTOS Drivers ‣ Enable pwm menu.

The following macro switches indicate that PWM3, PWM4, LPTIM3, PWMA1 and other devices are enabled:

#define RT_USING_PWM
#define BSP_USING_PWM 1
#define BSP_USING_PWM3 1
#define BSP_USING_PWM4 1
#define BSP_USING_PWM_LPTIM3 1
#define BSP_USING_PWMA1 1

Device Names

• pwm<x>: x is the device number, such as pwm2, pwm3. Note that device numbering starts from 2, device pwm2 corresponds to peripheral GPTIM1, pwm3 corresponds to peripheral GPTIM2, and so on

• pwmlp<x>: x is the device number, such as pwmlp1, pwmlp2, corresponding to peripherals LPTIM1 and LPTIM2

• pwma<x>: x is the device number, such as pwma1, corresponding to peripheral ATIM1

Example Code

// Find and open device
rt_device_t rt_device_find(const char *name);
  name: pwmlp1 / pwmlp3 / pwm3 / pwm4 /pwma1 ...

// Set
rt_err_t rt_pwm_set(struct rt_device_pwm *device, int channel, rt_uint32_t period, rt_uint32_t pulse);
  channel: 1-4 for GPTim, ignored for LPTim
  period: unit:ns 1ns~4.29s:1Ghz~0.23hz
  pulse:  unit:ns (pulse<=period)

// Start & Stop
rt_err_t rt_pwm_enable(struct rt_device_pwm *device, int channel);
rt_err_t rt_pwm_disable(struct rt_device_pwm *device, int channel);

//atimer deadtime break set
rt_err_t rt_pwm_set_brk_dead(struct rt_device_pwm *device, rt_uint32_t *bkd, rt_uint32_t dt_ns);
bkd: struct rt_pwm_break_dead config value
dt_ns: dead time ,unit ns. if dt_ns is 0, dead time use bkd->dtg (0~1023).

// example

{
    struct rt_device_pwm *device = RT_NULL;
	
	device = (struct rt_device_pwm *)rt_device_find("pwm3");
    if (!device)
    {
        return;
    }

    rt_pwm_set(device, 1, 500000000, 250000000);
    if (is_comp) //is pwm complementary
    {
        struct rt_pwm_break_dead bkd = {0};   // TODO: set the BKD.
        rt_pwm_set_brk_dead(device, (rt_uint32_t *)&bkd, 100);
        rt_pwm_enable2(device, channel, 1);
    }
    else
    {
        rt_pwm_enable(device, channel);
    }
    ......
    rt_pwm_disable(device, 1);
}

RT-Thread Reference Documentation

• PWM Device