eQEP增强型正交编码模块原理介绍及配合MircoE mercury II 4000光栅传感器使用

1、首先介绍MircoE mercury II 4000光栅传感器串口PIN及对应功能（male D-sub connector）

正交TTL电平（标准为低电平0，高电平1（+5v））

差分信号

由于光栅传感器一般意义上有转动和直线两种：

对于直线光栅来说，一般考虑的是位移信号，相对位移=（当前QPOSCNT的值- 开始时QPOSCNT的值）* 光栅分辨率（count / m）；

对于转动光栅来说，一般考虑的是机械角度和电角度，机械角度是空间转过一周的这一般分为两种计算转速的方式

1、在高速时，M测速法：

2、在低速时，T测速法：

void POSSPEED_Calc(POSSPEED *p)
{
     long tmp;
     unsigned int pos16bval,temp1;
   	 _iq Tmp1,newp,oldp;

//**** Position calculation - mechanical and electrical motor angle  ****//
     p->DirectionQep = EQep1Regs.QEPSTS.bit.QDF;    // Motor direction: 0=CCW/reverse, 1=CW/forward

	 pos16bval=(unsigned int)EQep1Regs.QPOSCNT;     // capture position once per QA/QB period
     p->theta_raw = pos16bval+ p->cal_angle;        // raw theta = current pos. + ang. offset from QA

	 // The following lines calculate 
     //p->theta_mech ~= QPOSCNT/mech_scaler [current cnt/(total cnt in 1 rev.)]
	 // where mech_scaler = 4000 cnts/revolution
     tmp = (long) ( (long)p->theta_raw * (long)p->mech_scaler );  	// Q0*Q26 = Q26
     tmp &= 0x03FFF000;
     p->theta_mech = (int)(tmp>>11);         		// Q26 -> Q15
     p->theta_mech &= 0x7FFF;

	 // The following lines calculate p->elec_mech
     p->theta_elec = p->pole_pairs * p->theta_mech;  // Q0*Q15 = Q15
     p->theta_elec &= 0x7FFF;

// Check an index occurrence
     if (EQep1Regs.QFLG.bit.IEL == 1)
     {
    	p->index_sync_flag = 0x00F0;
    	EQep1Regs.QCLR.bit.IEL=1;					// Clear interrupt flag
     }

//**** High Speed Calculation using QEP Position counter ****//
// Check unit Time out-event for speed calculation:
// Unit Timer is configured for 100Hz in INIT function

	if(EQep1Regs.QFLG.bit.UTO==1)                    // If unit timeout (one 100Hz period)
	{
		/** Differentiator	**/
		// The following lines calculate position = (x2-x1)/4000 (position in 1 revolution)
	 	pos16bval=(unsigned int)EQep1Regs.QPOSLAT;	              // Latched POSCNT value
     	tmp = (long)((long)pos16bval*(long)p->mech_scaler);  	  // Q0*Q26 = Q26
     	tmp &= 0x03FFF000;
     	tmp = (int)(tmp>>11);         			                  // Q26 -> Q15
     	tmp &= 0x7FFF;
		newp=_IQ15toIQ(tmp);
		oldp=p->oldpos;

   		if (p->DirectionQep==0)      				// POSCNT is counting down
   		{
    		if (newp>oldp)
      			Tmp1 = - (_IQ(1) - newp + oldp);    // x2-x1 should be negative
    		else
      		Tmp1 = newp -oldp;
   		}
   		else if (p->DirectionQep==1)      			// POSCNT is counting up
   		{
    		if (newp_IQ(1))
	     	p->Speed_fr = _IQ(1);
	   	else if (Tmp1<_IQ(-1))
	     	p->Speed_fr = _IQ(-1);
	   	else
	     	p->Speed_fr = Tmp1;

		// Update the electrical angle
    	p->oldpos = newp;

		// Change motor speed from pu value to rpm value (Q15 -> Q0)
		// Q0 = Q0*GLOBAL_Q => _IQXmpy(), X = GLOBAL_Q
   		p->SpeedRpm_fr = _IQmpy(p->BaseRpm,p->Speed_fr);
		//=======================================

		EQep1Regs.QCLR.bit.UTO=1;					// Clear interrupt flag
	}

//**** Low-speed computation using QEP capture counter ****//
	if(EQep1Regs.QEPSTS.bit.UPEVNT==1)                 // Unit position event
	{
		if(EQep1Regs.QEPSTS.bit.COEF==0)               // No Capture overflow
			temp1=(unsigned long)EQep1Regs.QCPRDLAT;   // temp1 = t2-t1
		else							               // Capture overflow, saturate the result
			temp1=0xFFFF;

		p->Speed_pr = _IQdiv(p->SpeedScaler,temp1);    // p->Speed_pr = p->SpeedScaler/temp1
		Tmp1=p->Speed_pr;

		if (Tmp1>_IQ(1))
	 		p->Speed_pr = _IQ(1);
		else
	 		p->Speed_pr = Tmp1;

	    // Convert p->Speed_pr to RPM
		if (p->DirectionQep==0)                                 // Reverse direction = negative
			p->SpeedRpm_pr = -_IQmpy(p->BaseRpm,p->Speed_pr); 	// Q0 = Q0*GLOBAL_Q => _IQXmpy(), X = GLOBAL_Q
		else                                                    // Forward direction = positive
			p->SpeedRpm_pr = _IQmpy(p->BaseRpm,p->Speed_pr); 	// Q0 = Q0*GLOBAL_Q => _IQXmpy(), X = GLOBAL_Q


		EQep1Regs.QEPSTS.all=0x88;					// Clear Unit position event flag
													// Clear overflow error flag
	}
}