伺服馬達控制

1. 伺服馬達控制
Joseph Chen

2. 360° Servo
伺服馬達控制主要利用PWM控制轉的方向
與轉速
360° servo 需要50Hz的脈波週期訊號 並藉由0.5~2.5ms HIGH PULSE做
控制
等於1.5ms HIGH PULSE是位於停止的狀態
小於1.5ms 順時針轉動, 若值愈小轉速可愈快
大於1.5ms 逆時針轉動,若值愈大轉速可愈快。

4. The S3C6410X RISC microprocessor comprises of
five 32-bit timers. These timers are used to
generate internal interrupts to the ARM
subsystem.
Timers 0 and 1 include a PWM function (Pulse
Width Modulation), which can drive an external
I/O signal. The PWM for timer 0 and 1 have an
optional dead-zone generator capability, which
can be utilized to support a large current device.
Timer 2, 3 and 4 are internal timers with no
output pins.

5. Clock Generation Scheme for PWM

6. PWM Function Block
TCNTB TCMPB
Manual Update=1
Auto reload=1
PCLK Prescaler Divder when TCNT reaches 0
TCNT TCMP TCNT=TCNB
TCMP=TCMPB
TCNTO
TCFG TCON
Double Buffering

7. PWM waveform

8. REGISTER MAP

10. S3C6410 的PWM 如何設定?
得到20ms的週期 (50HZ)
如果 PCLK=83MHZ, 8-bit prescaler=255 and 4-bit divider=16
Frequency=PCLK/(255+1)/16 => 20.2KHz
週期=>1/20.2K=0.0495ms
20ms/0.0495=404 --> TCNTB TOUT
Pulse Width
TCMPB setting?:
Get 2ms High Pulse width: 2ms/0.0495=40
Get 1.5ms High Pulse width: 1.5ms/0.0495=30
Get 1ms High Pulse width: 1ms/0.0495=20

11. dc_motor.c
static int __init dcm_init(void)
{
int retval;
retval = register_chrdev(DCM_MAJOR,dcm_name,&dcm_fops);
if(retval < 0)
{
printk(KERN_WARNING"Can't get major %dn",DCM_MAJOR);
return retval;
}
s3c6410_timer_setup(0,10,100,0);
pwm_init(PERIOD); //unit: 20000us
printk("Serveo_motor driver register success!n");
return 0;
}

12. static void pwm_init(unsigned long period)
{
Period=20000us
// initial the timer period
unsigned long tcnt;
時間(週期)
= Y HZ (Y次/s)* period
hi_pulse=0;
=次/s *(us/106)
tcnt=(period*(( PCLK )/((255+1)*16 )))/1000000;
printk(KERN_WARNING"%s:tcnt=%ldn",__func__,tcnt);
// tcnt =( 96000000 )/( FREQ_PWM1 *16 );
__raw_writel(tcnt, S3C_TCNTB(0));
__raw_writel(((tcnt*(0))/100), S3C_TCMPB(0));
}

13. s3c6410_timer_setup
int s3c6410_timer_setup (int channel, int usec,
unsigned long g_tcnt, unsigned long g_tcmp)
Parameters:
1) channel: PWM channel 0/1
2) usec: unused
3) g_tcnt: unused
4) g_tcmp: unused

14. /* set gpio as PWM TIMER0 to signal output*/
s3c_gpio_cfgpin(S3C64XX_GPF(14), S3C64XX_GPF14_PWM_TOUT0);
s3c_gpio_setpull(S3C64XX_GPF(14), S3C_GPIO_PULL_NONE);
tcfg1 &= ~S3C_TCFG1_MUX0_MASK;
tcfg1 |= 4; // set divider 16 , by jospeh
tcfg0 &= ~S3C_TCFG_PRESCALER0_MASK;
tcfg0 |= (PRESCALER) << S3C_TCFG_PRESCALER0_SHIFT;
tcon &= ~(7<<0);
tcon |= S3C_TCON_T0RELOAD;

15. User space Code
232, 0 /dev/pwm0
232,1 /dev/pwm1
fd_l=open(“/dev/pwm0”);
ioctl(fd_l,cmd,arg);
fd_r=open(“dev/pmm1”);
Ioctl(fd_r,cmd,arg)