The eighth chapter makes the Development Board sound: Buzzer driver

Through the study of the eighth chapter, I summed up some of my own thought important, need to master the knowledge points.

1. Control the buzzer sound by writing a specific value to the register.

2, in the encounter can not uninstall the Linux driver by directly modifying the Linux drive corresponding memory address to remove the Linux drive to avoid restarting the machine trouble.

3, through different source code files to store different function codes to facilitate the classification and management of code.

4, MAIN.C is the main program of Linux driver.

5. Initialize Linux drivers

Static int _init main _init (void)

6. Uninstalling Linux Drivers

Static void _exit main _exit (void)

7, register the function of initializing Linux driver

Module_init (Main_init);

8, register the function of uninstalling Linux driver

Module_exit (Main_exit);

9, code reuse is divided into static and dynamic two kinds,

10, forcibly uninstall the Linux driver occurs:

Initialization function crashes, unload functions are blocked,

11, through the corresponding register to control the buzzer open and close.

12, buzzer driving principle: Buzzer is also called PWM (pulse width modulation), the basic principle is to control the buzzer by pulse to open and close.

13. Open and close pwm via I/o command.

14. The close function of the PWM device file

Static int s3c64xx_pwm_close (struct inode *inode,struct file *file)

15. Releasing the semaphore

Up (&lock);

16. Open PWM

Pwm_start ();

17. Stop PWM

Pwm_stop ();

18. Initialize the semaphore

Init_motex (&lock);

19. Registration of equipment files

/dev/pwm_den

20. Removal of device files

Misc_deregister (&MISC);

21. I/o command, open PWM

#define PWM_IOCTL_START 1

22. I/o command; Stop PWM

#define PWM_IOCTL_STOP 0

23. Open PWM function

Extern void Pwm_start (void);

24, Stop the PWM function

Extern void pwm_stop (void);

25, the high two bits of the Gpfcon register are zeroed, the other bits are reserved

TMP &=~ (0x3u << 30);

26. Set the high two bit of the Gpfcon register to 10

TMP |= (0x2u << 30);

27, write the new value will Gpfcon register, PWM started screaming

IOWRITE32 (TMP, S3c64xx_gpfcon);

28, write the new value will Gpfcon register, PWM stop screaming

IOWRITE32 (TMP, S3c64xx_gpfcon);

29. Open PWM

#./ioctl/dev/pwm_dev 1 0

30. Stop PWM

#./ioctl/dev/pwm_dev 0 0

The eighth chapter makes the Development Board sound: Buzzer driver