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PWM Example*

Note

1. Overview*

PWM output example App, demonstrating how to use the PWM (Pulse Width Modulation) function on the chip to implement periodic PWM signal on/off control.

2. Features*

  • Dual-channel PWM signal output (PAD 5 + PAD 6)
  • Automatic timed toggling of PWM on/off state (5-second period by default)
  • Pin and parameter configuration via macro definitions for easy modification

3. Directory Structure*

app/pwm_app/
├── app.c       # Main program
├── app.mk       # Build configuration
├── app.name     # Kconfig option
└── Kconfig      # Sub-configuration (empty)
File Description
app.c Main program, PWM initialization and timed toggling logic
app.mk Builds app.c
app.name Defines the CONFIG_APP_PWM option

4. Configuration Description*

4.1 Macro Definitions*

// PWM pin and Timer configuration
#define PWM_PIN_1           5       // First PWM pin
#define PWM_TIMER_1         5       // Timer corresponding to the first PWM
#define PWM_PIN_2           6       // Second PWM pin
#define PWM_TIMER_2         0       // Timer corresponding to the second PWM

// PWM signal parameters
#define PWM_PERIOD_NS       100000000   // PWM period: 100ms (nanoseconds)
#define PWM_DUTY_NS         50000000    // PWM duty cycle: 50ms (50%) (nanoseconds)

// Pin multiplexing configuration
#define PWM_PADMUX_PWM      3           // Pin multiplexed as PWM function
#define PWM_PADMUX_GPIO     7           // Pin multiplexed as GPIO function

// Toggle time configuration
#define TOGGLE_INTERVAL_MS  5000        // Toggle interval: 5 seconds
#define EVENT_PERIOD_MS     40          // Event trigger period: 40ms
#define TOGGLE_COUNT        (TOGGLE_INTERVAL_MS / EVENT_PERIOD_MS)  // Auto-calculated: 125 times

4.2 Pin Mapping*

Pin Timer Multiplexed Function Description
PAD 5 Timer5 PWM (padmux=3) PWM channel 1
PAD 6 Timer0 PWM (padmux=3) PWM channel 2

4.3 PWM API*

gx_timer_enable_pwm_get(timer_id, port, period_ns, duty_ns);
Parameter Description
timer_id Timer number
port Pin number
period_ns PWM period (nanoseconds), 100000000ns = 100ms
duty_ns High-level duration (nanoseconds), 50000000ns = 50ms (50% duty cycle)

5. Working Principle*

5.1 Initialization Flow*

  1. Configure the pin multiplexing of PAD 5 and PAD 6 to PWM function (padmux_set(pin, 3))
  2. Enable Timer5 and Timer0 to generate PWM signals
  3. The initial PWM state is ON

5.2 Event Handling*

The EVENT_AUDIO_IN_RECORD_DONE event is used to implement timed toggling:

Event Trigger Condition Processing Logic
EVENT_AUDIO_IN_RECORD_DONE Audio-in recording complete (trigger time determined by PCM frame length, configure accordingly) Increment counter, toggle PWM state when reaching 125 counts (5 seconds)

5.3 Main Loop*

app_task_loop() is an empty implementation.

5.4 State Transition*

Initialization → PWM ON → (after 5 seconds) → PWM OFF → (after 5 seconds) → PWM ON → ...

Toggle logic: - PWM ON → call gx_timer_disable_pwm() to disable the Timer PWM, switch the pin to GPIO input mode - PWM OFF → reconfigure the pin multiplexing to PWM, enable Timer PWM output

6. Usage*

6.1 Build*

cp configs/example/app/8006_pwm_app.config .config
make defconfig
make clean; make

Or select via menuconfig:

make menuconfig
# OVP Application Settings → Applications Selection → PWM Sample

6.2 Flash and Run*

cd tools/bootx/
./flash_nor.sh 0 -r 1000000

7. Expected Output*

The serial port (921600 baud rate) outputs alternating logs:

[PWM_APP] Open PWM
[PWM_APP] Close PWM
[PWM_APP] Open PWM
...

Approximately 0.2 logs per second (toggling every 5 seconds).

8. Notes*

  1. 8005 Pin Differences: The PWM pins on the 8005 chip differ from those on the 8006. When using the 8005, modify the PWM_PIN_1 and PWM_PIN_2 macro definitions according to the chip datasheet.
  2. Timer Conflict: In the SDK, Timer5 is occupied by the system by default. To use another Timer, modify the MCU_TIMER_ID configuration item via make menuconfig: 
    MCU settings  --->
   (5) Timer ID For gx_get_time_ms  # Modify this configuration
  3. Pin Multiplexing: Not all pins support the PWM function. Refer to the chip datasheet to confirm the pin multiplexing capabilities.
  4. Chip Datasheet Reference: GX8006 Datasheet - Pin Multiplexing Description
  5. PWM Disable Operation: When disabling PWM, the following steps are required:
  6. Disable the Timer PWM function
  7. Set the pin to GPIO mode
  8. Configure the GPIO as input mode (to avoid output interference)
  9. Suspend/Resume Not Implemented: The current SDK does not support the suspend function. app_suspend() and app_resume() can remain as empty implementations.

9. Troubleshooting*

Symptom Possible Cause Solution
No PWM output Incorrect pin multiplexing configuration Refer to the chip datasheet to confirm the padmux_set() parameter; the PWM mode value is 3
Timer initialization failure Timer occupied by the system Use a different Timer or modify the MCU_TIMER_ID configuration