PWM

This example achieves outputting a PWM waveform by using ENHTIM.

Connect P0_0（PWM_P） and P0_1（PWM_N）to the logic analyzer, where you can observe the output waveform of the PWM.

Requirements

For requirements, please refer to the Requirements.

Wiring

Connect P0_0（PWM_P） and P0_1（PWM_N）to a logic analyzer.

Configurations

The following macro can be configured to modify the output PWM wave pin.

#define PWM_OUT_P_PIN                     P0_0
#define PWM_OUT_N_PIN                     P0_1

You can configure the following macros to modify the frequency and duty cycle of the PWM.

#define PWM_PERIOD                        100                                         /*< Setting this macro to 100 means the output is a PWM wave with a period of 100us. The unit of this macro is microseconds (us). */
#define PWM_DUTY_CYCLE                    50                                          /*< Setting this macro to 50 means the output is a PWM wave with a 50% duty cycle. */
#define PWM_MAXCNT                        (PWM_PERIOD * 40)
#define PWM_CCVALUE                       (((PWM_PERIOD)*(PWM_DUTY_CYCLE*40))/100)

The following macros can be configured to select whether a waveform with continuously varying duty cycle can be output.

#define ENHTIM_PWM_MANUAL_MODE            1                                           /*< Setting this macro to 1 means that a PWM waveform with a period of 100us and a duty cycle of 50% can be output. */
#define ENHTIM_PWM_AUTO_MODE              0                                           /*< Setting this macro to 1 means that a waveform with a period of 100us and continuously varying duty cycle can be output. */

Building and Downloading

For building and downloading, please refer to the Building and Downloading.

Experimental Verification

After the EVB starts, you can observe the PWM waveform using a logic analyzer on the P0_0 and P0_1 pins.

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

PWM Output Waveform in Manual Mode

b. If the configuring macro ENHTIM_PWM_AUTO_MODE is set to 1, P0_0 outputs a PWM waveform with a period of 100us and duty cycles of 100%, 80%, 60%, 50%, 30%, 20%, 10%, 0%. Subsequently, the output PWM waveform will maintain the duty cycle set during the last configuration. The P0_1 output will be an inverted PWM wave with the same period and duty cycle as P0_0.

PWM Output Waveform in Auto Mode

Code Overview

This section mainly introduces the code and process description for initialization and corresponding function implementation in the example.

Source Code Directory

The directory for project file and source code are as follows:

Project directory: sdk\samples\peripheral\enhtimer\enhtim_pwm\proj
Source code directory: sdk\samples\peripheral\enhtimer\enhtim_pwm\src

Initialization

The initialization flow for peripherals can refer to Initialization Flow in General Introduction.

Call Pad_Config() and Pinmux_Config() to configure the PAD and PINMUX of the corresponding pins.

void board_enhance_pwm_init(void)
{
    Pad_Config(PWM_OUT_P_PIN, PAD_PINMUX_MODE, PAD_IS_PWRON, PAD_PULL_NONE, PAD_OUT_ENABLE, PAD_OUT_HIGH);
    Pad_Config(PWM_OUT_N_PIN, PAD_PINMUX_MODE, PAD_IS_PWRON, PAD_PULL_NONE, PAD_OUT_ENABLE, PAD_OUT_HIGH);

    Pinmux_Config(PWM_OUT_P_PIN, PWM_PINMUX_OUT_P);
    Pinmux_Config(PWM_OUT_N_PIN, PWM_PINMUX_OUT_N);
}

Call RCC_PeriphClockCmd() to enable the ENHTIM clock.
Initialize the ENHTIM peripheral:
1. Define the ENHTIM_InitTypeDef type ENHTIM_InitStruct, and call ENHTIM_StructInit() to pre-fill ENHTIM_InitStruct with default values.
2. Modify the ENHTIM_InitStruct parameters according to the requirements. When selecting different ENHTIM Modes, the initialization configuration parameters vary. The initialization parameter configuration for ENHTIM is shown in the table below. Call ENHTIM_Init() to initialize the ENHTIM peripheral.

ENHTIM Initialization Parameters
ENHTIM Hardware Parameters	Setting in the `ENHTIM_InitStruct`	ENHTIM manual mode	ENHTIM auto mode
Counter mode	`ENHTIM_InitTypeDef::ENHTIM_Mode`	`ENHTIM_MODE_PWM_MANUAL`	`ENHTIM_MODE_PWM_AUTO`
PWM mode	`ENHTIM_InitTypeDef::ENHTIM_PWMOutputEn`	`ENABLE`	`ENABLE`
Toggle output polarity	`ENHTIM_InitTypeDef::ENHTIM_PWMStartPolarity`	`ENHTIM_PWM_START_WITH_HIGH`	`ENHTIM_PWM_START_WITH_HIGH`
Count value	`ENHTIM_InitTypeDef::ENHTIM_MaxCount`	`PWM_MAXCNT`	`PWM_MAXCNT`
Capture/Compare value	`ENHTIM_InitTypeDef::ENHTIM_CCValue`	`PWM_CCVALUE`	-
PWM deadzone clock source	`ENHTIM_InitTypeDef::ENHTIM_PWMDeadZoneClockSource`	`ENHTIM_PWM_DZCLKSRCE_32K`	`ENHTIM_PWM_DZCLKSRCE_32K`
PWM deadzone function	`ENHTIM_InitTypeDef::ENHTIM_PWMDeadZoneEn`	`ENABLE`	`ENABLE`
PWM P stop state	`ENHTIM_InitTypeDef::ENHTIM_PWMStopStateP`	`ENHTIM_PWM_STOP_AT_HIGH`	`ENHTIM_PWM_STOP_AT_HIGH`
PWM N stop state	`ENHTIM_InitTypeDef::ENHTIM_PWMStopStateN`	`ENHTIM_PWM_STOP_AT_LOW`	`ENHTIM_PWM_STOP_AT_LOW`
Size of deadzone time	`ENHTIM_InitTypeDef::ENHTIM_DeadZoneSize`	0x0	0x0

If the macro ENHTIM_PWM_AUTO_MODE is set to 1, call ENHTIM_WriteCCFIFO() to pre-fill the duty cycle of the output waveform.
Call ENHTIM_Cmd() to enable the ENHTIM peripheral, and the PWM output waveform can be observed within the logic analyzer.

Functional Implementation

The process for ENHTIM to output PWM in manual mode and auto mode is shown in the figure:

Here should be enhtim pwm flow — ENHTIM PWM Output flow in Different Modes

In ENHTIM_MODE_PWM_MANUAL mode, it is necessary to set ENHTIM_InitTypeDef::ENHTIM_CCValue to modify the duty cycle of the output PWM.

In ENHTIM_MODE_PWM_AUTO mode, it is necessary to call ENHTIM_WriteCCFIFO() to modify the duty cycle value of the output PWM.

ENHTIM_WriteCCFIFO(Enhance_Timer, 0); //Output high level with a duty cycle of 100%
ENHTIM_WriteCCFIFO(Enhance_Timer, 800); //Output high level with a duty cycle of 80%
ENHTIM_WriteCCFIFO(Enhance_Timer, 1600); //Output high level with a duty cycle of 60%
ENHTIM_WriteCCFIFO(Enhance_Timer, 2000); //Output high level with a duty cycle of 50%
ENHTIM_WriteCCFIFO(Enhance_Timer, 2800); //Output high level with a duty cycle of 30%
ENHTIM_WriteCCFIFO(Enhance_Timer, 3200); //Output high level with a duty cycle of 20%
ENHTIM_WriteCCFIFO(Enhance_Timer, 3600); //Output high level with a duty cycle of 10%
ENHTIM_WriteCCFIFO(Enhance_Timer, 4000); //Output low level with a duty cycle of 100%

Sequentially pre-fill data into the CCR FIFO, representing duty cycles of 100%, 80%, 60%, 50%, 30%, 20%, 10%, and 0%.
If the CCR FIFO is not cleared and new values are written into it, the subsequent output PWM waveform will maintain the last set duty cycle.