Enhance Timer PWM

This sample demonstrates the generation of a PWM waveform with a period of 100us and a duty cycle of 50%.

In the example, configure the macros ENHTIM_PWM_MANUAL_MODE and ENHTIM_PWM_AUTO_MODE to select whether the duty cycle of the output PWM waveform is variable or not.

If ENHTIM_PWM_MANUAL_MODE is selected, a PWM waveform with a period of 100us and a duty cycle of 50% can be output.

If ENHTIM_PWM_AUTO_MODE is selected, a PWM waveform with a period of 2.5us and an adjustable duty cycle can be output.

Requirements

The sample supports the following development kits:

Development Kits

Hardware Platforms

Board Name

RTL87x2G HDK

RTL87x2G EVB

For more requirements, please refer to Quick Start.

Wiring

Connect P0_0 and P0_1 to a logic analyzer.

Configurations

The example configurable macros are as follows:

  1. ENHTIM_PWM_AUTO_MODE: Configuring this macro selects the output mode as auto mode. In auto mode, the duty cycle of the output PWM waveform can be pre-set, i.e., output PWM with a variable duty cycle.

  2. ENHTIM_PWM_MANUAL_MODE: Configure this macro to select the output mode as user-defined manual mode. In manual mode, a PWM with a fixed duty cycle can be output.

Building and Downloading

This sample can be found in the SDK folder:

Project file: samples\peripheral\enhtimer\enhtim_pwm\proj\rtl87x2g\mdk

Project file: samples\peripheral\enhtimer\enhtim_pwm\proj\rtl87x2g\gcc

To build and run the sample, follow the steps listed below:

  1. Open sample project file.

  2. To build the target, follow the steps listed on the Generating App Image in Quick Start.

  3. After a successful compilation, the app bin app_MP_xxx.bin will be generated in the directory mdk\bin or gcc\bin.

  4. To download app bin into EVB board, follow the steps listed on the MP Tool Download in Quick Start.

  5. Press reset button on EVB board and it will start running.

Experimental Verification

  1. Connect the logic analyzer to P0_0 and P0_1 pins to observe the PWM waveforms being output.

    1. If the output PWM mode is selected to be ENHTIM_PWM_MANUAL_MODE, the P0_0 output will be a PWM wave with a period of 100 us and a duty cycle of 50%. The P0_1 output will be an inverted PWM wave with the same period and duty cycle as P0_0.

      Here should be the picture of the PWM waveform output by enhtim

      PWM Output Waveform in Manual Mode

    2. If the output PWM mode is selected to be ENHTIM_PWM_AUTO_MODE, P0_0 outputs a PWM waveform with a period of 2.5us, in which the duty cycle is changed from 100% to 0% in sequence 8 times. After changing the duty cycle 8 times, the subsequent PWM output waveforms will maintain the duty cycle of the last setting. The P0_1 output will be an inverted PWM wave with the same period and duty cycle as P0_0.

      Here should be the picture of the PWM waveform output by enhtim

      PWM Output Waveform in Auto Mode

Code Overview

This chapter will be introduced according to the following several parts:

  1. Source Code Directory.

  2. Peripheral initialization will be introduced in chapter Initialization.

Source Code Directory

  1. Project Directory: sdk\samples\peripheral\enhtimer\enhtim_pwm\proj

  2. Source Code Directory: sdk\samples\peripheral\enhtimer\enhtim_pwm\src

Source files are currently categorized into several groups as below.

└── Project: input_interrupt
    └── secure_only_app
        └── Device                   includes startup code
            ├── startup_rtl.c
            └── system_rtl.c
        ├── CMSIS                    includes CMSIS header files
        ├── CMSE Library             Non-secure callable lib
        ├── Lib                      includes all binary symbol files that user application is built on
            └── rtl87x2g_io.lib
        ├── Peripheral               includes all peripheral drivers and module code used by the application
            ├── rtl_rcc.c
            ├── rtl_pinmux.c
            └── rtl_enh_tim.c
        └── APP                      includes the ble_peripheral user application implementation
            ├── main_ns.c
            └── io_enhtimer_pwm.c

Initialization

The initialization process includes board_enhance_pwm_init and enhance_timer_init.

board_enhance_pwm_init contains the PAD and PINMUX settings.

  1. Configure PAD: Set the pins as PINMUX mode, PowerOn, internal Pull-Up.

  2. Configure PINMUX: Assign the pins for PWM_P and PWM_N functionality respectively.

enhance_timer_init contains the initialization of ENHTIM peripherals.

  1. Enable PCC clock.

  2. Set ENHTIM_ClockDiv to a clock frequency divider of 1.

  3. If the output PWM mode is selected to be ENHTIM_PWM_AUTO_MODE :

    1. Set ENHTIM_PWMOutputEn to ENABLE to enable the PWM functionality of ENHTIM.

    2. Set ENHTIM_PWMStartPolarity to ENHTIM_PWM_START_WITH_HIGH, that is, set the initial output level of the PWM to high.

    3. Set ENHTIM_MaxCount to 100, which means the output period of the PWM is 2.5us.

    4. If needing to change the duty cycle of the PWM output, the ENHTIM_WriteCCFIFO() function can be used to make the changes. This function supports a maximum of 8 consecutive changes.

  4. If the output PWM mode is selected to be ENHTIM_PWM_MANUAL_MODE :

    1. Set ENHTIM_PWMOutputEn to ENABLE to enable the PWM function of ENHTIM.

    2. Set ENHTIM_PWMStartPolarity to ENHTIM_PWM_START_WITH_HIGH to initialize the PWM output level as high.

    3. Set ENHTIM_MaxCount to 4000 to set the PWM output period as 100us.

    4. Set ENHTIM_CCValue to 2000 to set the PWM duty cycle as 50% (2000/4000).

  5. Set ENHTIM_PWMDeadZoneClockSource to ENHTIM_PWM_DZCLKSRCE_32K to set the clock source for the PWM dead zone as 32k.

  6. Set ENHTIM_PWMDeadZoneEn to ENABLE to enable the dead zone function of the PWM.

  7. Set ENHTIM_PWMStopStateP to ENHTIM_PWM_STOP_AT_HIGH to set the initial level of PWM_P output to high.

  8. Set ENHTIM_PWMStopStateN to ENHTIM_PWM_STOP_AT_LOW to set the initial level of PWM_N output to low.

  9. Set ENHTIM_DeadZoneSize to 0x0.

  RCC_PeriphClockCmd(APBPeriph_ENHTIMER, APBPeriph_ENHTIMER_CLOCK, ENABLE);
  ...
  ENHTIM_InitStruct.ENHTIM_ClockDiv = ENHTIM_CLOCK_DIVIDER_1;

#if ENHTIM_PWM_AUTO_MODE
  ENHTIM_InitStruct.ENHTIM_Mode               = ENHTIM_MODE_PWM_AUTO;
  ENHTIM_InitStruct.ENHTIM_PWMOutputEn        = ENABLE;
  ENHTIM_InitStruct.ENHTIM_PWMStartPolarity   = ENHTIM_PWM_START_WITH_HIGH;
  ENHTIM_InitStruct.ENHTIM_MaxCount           = 100;
#endif

#if ENHTIM_PWM_MANUAL_MODE
  ENHTIM_InitStruct.ENHTIM_Mode = ENHTIM_MODE_PWM_MANUAL;
  ENHTIM_InitStruct.ENHTIM_PWMOutputEn = ENABLE;
  ENHTIM_InitStruct.ENHTIM_PWMStartPolarity = ENHTIM_PWM_START_WITH_HIGH;
  ENHTIM_InitStruct.ENHTIM_MaxCount = 4000;
  ENHTIM_InitStruct.ENHTIM_CCValue = 2000;
#endif

  ENHTIM_InitStruct.ENHTIM_PWMDeadZoneClockSource = ENHTIM_PWM_DZCLKSRCE_32K;
  ENHTIM_InitStruct.ENHTIM_PWMDeadZoneEn = ENABLE;
  ENHTIM_InitStruct.ENHTIM_PWMStopStateP = ENHTIM_PWM_STOP_AT_HIGH;
  ENHTIM_InitStruct.ENHTIM_PWMStopStateN = ENHTIM_PWM_STOP_AT_LOW;
  ENHTIM_InitStruct.ENHTIM_DeadZoneSize = 0x0;

  ENHTIM_Init(Enhance_Timer, &ENHTIM_InitStruct);

#if ENHTIM_PWM_AUTO_MODE
  /* After the waveform is transformed 8 times,
  the PWM maintains the last change and continues to output */
  ENHTIM_WriteCCFIFO(Enhance_Timer, 0); //Output high level with a duty cycle of 100%
  ENHTIM_WriteCCFIFO(Enhance_Timer, 20); //Output high level with a duty cycle of 80%
  ENHTIM_WriteCCFIFO(Enhance_Timer, 40); //Output high level with a duty cycle of 60%
  ENHTIM_WriteCCFIFO(Enhance_Timer, 50); //Output high level with a duty cycle of 50%
  ENHTIM_WriteCCFIFO(Enhance_Timer, 70); //Output high level with a duty cycle of 30%
  ENHTIM_WriteCCFIFO(Enhance_Timer, 80); //Output high level with a duty cycle of 20%
  ENHTIM_WriteCCFIFO(Enhance_Timer, 90); //Output high level with a duty cycle of 10%
  ENHTIM_WriteCCFIFO(Enhance_Timer, 100); //Output low level with a duty cycle of 100%
#endif

  ENHTIM_Cmd(Enhance_Timer, ENABLE);