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Fujitsu Microelectronics Europe
Application Note
MCU-AN-300231-E-V12
F²MC-16FX FAMILY
16-BIT MICROCONTROLLER
MB96380
STEPPER MOTOR CONTROLLER
APPLICATION NOTE
Stepper Motor Controller
Revision History
Revision History
Date
2006-06-11
2007-09-24
2007-09-28
Issue
V1.0, PHu
Initial Version, based on spectrum article of JMe
V1.1 HPi
Updated Example
V1.2 HPi
Updated Code formatting
This document contains 14 pages.
MCU-AN-300231-E-V12
-2-
© Fujitsu Microelectronics Europe GmbH
Stepper Motor Controller
Warranty and Disclaimer
Warranty and Disclaimer
To the maximum extent permitted by applicable law, Fujitsu Microelectronics Europe GmbH restricts
its warranties and its liability for all products delivered free of charge (e.g. software include or
header files, application examples, target boards, evaluation boards, engineering samples of IC’s
etc.), its performance and any consequential damages, on the use of the Product in accordance with
(i) the terms of the License Agreement and the Sale and Purchase Agreement under which
agreements the Product has been delivered, (ii) the technical descriptions and (iii) all accompanying
written materials. In addition, to the maximum extent permitted by applicable law, Fujitsu
Microelectronics Europe GmbH disclaims all warranties and liabilities for the performance of the
Product and any consequential damages in cases of unauthorised decompiling and/or reverse
engineering and/or disassembling. Note, all these products are intended and must only be used
in an evaluation laboratory environment.
1.
Fujitsu Microelectronics Europe GmbH warrants that the Product will perform substantially in
accordance with the accompanying written materials for a period of 90 days form the date of
receipt by the customer. Concerning the hardware components of the Product, Fujitsu
Microelectronics Europe GmbH warrants that the Product will be free from defects in material
and workmanship under use and service as specified in the accompanying written materials
for a duration of 1 year from the date of receipt by the customer.
2.
Should a Product turn out to be defect, Fujitsu Microelectronics Europe GmbH´s entire liability
and the customer´s exclusive remedy shall be, at Fujitsu Microelectronics Europe GmbH´s
sole discretion, either return of the purchase price and the license fee, or replacement of the
Product or parts thereof, if the Product is returned to Fujitsu Microelectronics Europe GmbH in
original packing and without further defects resulting from the customer´s use or the transport.
However, this warranty is excluded if the defect has resulted from an accident not attributable
to Fujitsu Microelectronics Europe GmbH, or abuse or misapplication attributable to the
customer or any other third party not relating to Fujitsu Microelectronics Europe GmbH.
3.
To the maximum extent permitted by applicable law Fujitsu Microelectronics Europe GmbH
disclaims all other warranties, whether expressed or implied, in particular, but not limited to,
warranties of merchantability and fitness for a particular purpose for which the Product is not
designated.
4.
To the maximum extent permitted by applicable law, Fujitsu Microelectronics Europe GmbH´s
and its suppliers´ liability is restricted to intention and gross negligence.
NO LIABILITY FOR CONSEQUENTIAL DAMAGES
To the maximum extent permitted by applicable law, in no event shall Fujitsu
Microelectronics Europe GmbH and its suppliers be liable for any damages whatsoever
(including but without limitation, consequential and/or indirect damages for personal
injury, assets of substantial value, loss of profits, interruption of business operation,
loss of information, or any other monetary or pecuniary loss) arising from the use of
the Product.
Should one of the above stipulations be or become invalid and/or unenforceable, the remaining
stipulations shall stay in full effect
© Fujitsu Microelectronics Europe GmbH
-3-
MCU-AN-300231-E-V12
Stepper Motor Controller
Contents
Contents
REVISION HISTORY ............................................................................................................ 2
WARRANTY AND DISCLAIMER ......................................................................................... 3
CONTENTS .......................................................................................................................... 4
1 INTRODUCTION.............................................................................................................. 5
2 STEPPER MOTOR .......................................................................................................... 6
2.1
Stepper Motor physics............................................................................................. 6
2.2
Control Theory ........................................................................................................ 7
2.3
Code ....................................................................................................................... 9
3 APPENDIX ..................................................................................................................... 13
3.1
Figures .................................................................................................................. 13
4 ADDITIONAL INFORMATION ....................................................................................... 14
MCU-AN-300231-E-V12
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© Fujitsu Microelectronics Europe GmbH
Stepper Motor Controller
Chapter 1 Introduction
1 Introduction
The MB96380 Series of MCUs features Stepper Motor Controllers (SMC). The function and
usage of the SMCs is explained in this application note. For a full understanding, the
functioning of a Stepper Motor is considered.
© Fujitsu Microelectronics Europe GmbH
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MCU-AN-300231-E-V12
Stepper Motor Controller
Chapter 2 Stepper Motor
2 Stepper Motor
The SMC can easily be used for very smooth movement of a stepper motor as for example
an indication application. Therefore the physical characteristics and properties have to be
well known and understood.
2.1
Stepper Motor physics
For operation it might be useful to have a small introduction, what happens with the physics.
In this explanation, we will use a simple replacement model for the stepper motor as a
replacement circuitry. It represents the rotor as one bipolar magnet and two coils which are
arranged perpendicular to each other as the stator (Figure 1).
Ix
N
S
Iy
Figure 1: Replacement circuit for Stepper Motor
To meet the necessities of a really smooth movement, we have to insure that the torque
moment is constant while the whole movement is performed. The preparation of this is done
by adding the single coil components in a geometrical manner to a constant result (Figure 2).
Normally to realise this, we use sine and cosine components for each coil. Therefore, with
this model, we can position the rotor in each random position with the same torque moment.
Fy
Iy
Fr
Ix
Fx
Figure 2: Torque Moment calculation
MCU-AN-300231-E-V12
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© Fujitsu Microelectronics Europe GmbH
Stepper Motor Controller
Chapter 2 Stepper Motor
For a movement, we have to perform a follow up of positions between a Start and a Stop
position. While controlling usual stepper motors as real stepping devices, this is done with a
step by step method (Figure 3). So, the movement has constant speed while moving. That is
not suitable for smooth movement, e.g. if the motor arrives at the stop position it stops then
abruptly.
(t)
(t)
(t)
Zone B
2
2
1
1
2
1
t
Zone A
Zone A
Figure 3: Without filter, with 1st order LP filter, and with 2nd order LP filter
To improve this, a low-pass filter is used. The low-pass filter solves the problem at the stop
point (Figure 3). Nevertheless, the same problem exists at the starting point. To solve this,
we use a second order low-pass filter. The second order low-pass filter solves the problem
at the start point (Figure 3), but it sets up the necessities of a maximum Speed and a max.
acceleration, which depends on the way of the movement.
Otherwise the motor itself has a physically given maximum speed and acceleration. To
insure that the required properties do not overtake the given physics, we use an acceleration
and velocity clipper. This clipper must be integrated into the 2nd order LP-filter, which must
equalise the clipped edges.
The realisation of a second order low-pass filter can be done by simply combining two
stages of a 1st order LP-Filter. The 1st order LP-Filter can be performed by a simple
mathematical formula like this:
PT1i =
2.2
Xini + ( PT 1i 1 * n)
n +1
PT2i =
PT1i + (PT2i 1 * n)
n +1
Control Theory
To implement the required 2nd order LP-filter in a way to get a fast calculation of it, it is useful
to perform
i.)
Y1st_new= (((Y1st_old<<n) -Y1st_old) +Xin_new) >>n
ii.)
Y2nd_new= (((Y2nd_old<<n) -Y2nd_old) +Y1st_new) >>n
This way, only two shift operations and two subtractions have to be performed. This saves
CPU Duty cycles.
This operation has to be performed repetitively in a given time. The difference between the
new output value at this time and the last output value at the last time is the velocity. So the
actual speed of the requested movement can be evaluated by a simple subtraction.
If we store the actual speed in a memory cell, we can subtract the actual speed from the
speed of the last time. The result is the actual acceleration. The physical units are as follows:
© Fujitsu Microelectronics Europe GmbH
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MCU-AN-300231-E-V12
Stepper Motor Controller
Chapter 2 Stepper Motor
Vact =
PT 2 i
PT 2 i
t2
1
t1
and
a act =
Vi Vi
1
t 2 t1
Or more suitable for programming:
phi_1 - phi_2 = d_phi
t1 - t2 = d_t
velo = d_phi / d_t
acc = ( d_phi1 - d_phi2 ) / ( ( d_t ) * (d_t) ) ; same as dphi² / dt²
To clip them at a given moment, we have to check whether they reach the limits.
velo_new = Y2nd_new - Y2nd_old
For sample we compare them to given constants. If they are beyond the limit, we replace the
new output value with substitutes from the physical evaluation.
velo_new = Y2nd_new - Y2nd_old
if ( velo_new - velo_old ) > max.acceleration.constant then
max.Velo.actual = velo_old + max.acc.constant
else
max.velo.actual = max.velo.constant
endif
if velo_new > max.velo.actual then
Y2nd_new = Y2nd_old + max.velo.actual
Endif
By using these equations a few hundred times per second (repetitively time is only a few
milliseconds), we will succeed to earn a smooth movement of our pointer in this application.
In practical use, the damping value n should be in the range of 3..6, because of the
characteristics of the 2nd order LP-filter.
As an example, we can use lookup tables to cover the line switching at the output pins for
the motor. Herewith a sample of an output function for the stepper motor macro which uses
a 128 microsteps per quadrant sine and cosine lookup table. Otherwise, the given pre-set
value for this function is normalised to 256 microsteps per quadrant. Therefore, we can
easily change the resolution for a given
Coil_A
application from 0..7 Bits per quadrant,
Coil_B
--> microSteps
simply by changing the shift operation for
256
normalising and fetching the sine / cosine
192
tables with the necessary length.
128
CPU_Pin : PWM2Mx
+ Coil_B ( - COS )
CPU_Pin : PWM2Px
+ Coil_B ( + COS )
CPU_Pin : PWM1Px
+ Coil_A ( + SIN )
CPU_Pin : PWM1Mx
- Coil_A ( - SIN )
64
0
-64 0
256
768
1024
-128
-192
-256
Quadr 0
MCU-AN-300231-E-V12
512
-8-
Quadr 1
Quadr 2
Quadr 3
© Fujitsu Microelectronics Europe GmbH
Stepper Motor Controller
Chapter 2 Stepper Motor
2.3
Code
Now we can realise this as a simple output function:
/* sin/cos Lookup table for microstepping */
unsigned char const SMC_TAB_CS[129]={
0, 3, 6, 9, 13, 16, 19, 22,
25, 28, 31, 34, 37, 41, 44, 47,
50, 53, 56, 59, 62, 65, 68, 71,
74, 77, 80, 83, 86, 89, 92, 95,
98,100,103,106,109,112,115,117,
120,123,126,128,131,134,136,139,
142,144,147,149,152,154,157,159,
162,164,167,169,171,174,176,178,
180,183,185,187,189,191,193,195,
197,199,201,203,205,207,208,210,
212,214,215,217,219,220,222,223,
225,226,228,229,231,232,233,234,
236,237,238,239,240,241,242,243,
244,245,246,247,247,248,249,249,
250,251,251,252,252,253,253,253,
254,254,254,255,255,255,255,255,
255 };
/* Lookup tables for quadrant management */
unsigned char const smc_quad_a[4]={0x02, 0x10, 0x10, 0x02};
unsigned char const smc_quad_b[4]={0x50, 0x50, 0x42, 0x42};
void
}
smc_out(int ustp) {
int q,d,smc_a,smc_b;
q=((ustp>>8) & 3);
/* some squeeze intermediate memories
/* normalise the over all granulation
to 1024 microsteps per polpair change
d=((ustp>>1) & 127);
/* normalise the inner granulation
to 512 microsteps per polpair change
so that the Bit0 of ustp is don't care!
smc_a=SMC_TAB_CS[d];
/* preload of sin component
smc_b=SMC_TAB_CS[128-d];/* preload of cos component
note the trick with the enlarged table,
which can be used in reverse order
if ((q & 1)==1) {
/* decide where to go whatever
PWC10=smc_a;
/* set up the sin value for coil A
PWC20=smc_b;
/* set up the cos value for coil B
}
else {
/* otherwise change the signs
PWC10=smc_b;
/* set up the cos value for coil A
PWC20=smc_a;
/* set up the sin value for coil B
}
PWC0=0xE8;
/* startover with the resource operation
PWS10=smc_quad_a[q];
/* arming the signal for coil A
PWS20=smc_quad_b[q];
/* arming the signal for coil B
*/
*/
*/
*/
*/
*/
*/
*/
*/
*/
*/
*/
*/
*/
This output driver routine is hopefully a balanced finish between minimised memory
requirements and clear viewing of coding effects.
Herewith an example of a 2nd order low-pass filter interrupt service routine to support the
output function for the Stepper motor.
© Fujitsu Microelectronics Europe GmbH
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MCU-AN-300231-E-V12
Stepper Motor Controller
Chapter 2 Stepper Motor
void
smc__lpf(void) {
/* this tiny calculation should be done
in a less part of a millisecond
*/
smc_old=smc_new;
/* yesterdays future is passed today */
/* first order low pass filter */
*((int *)&smc_clc1+1)=smc_inp;
/* normalise input value
smc_clc1=(smc_clc1>>smc_dn);
smc_clc2=(smc_pt1-(smc_pt1>>smc_dn));
smc_pt1=smc_clc2+smc_clc1;
*/
/* second order low pass filter */
smc_clc2=(smc_pt2-(smc_pt2>>smc_dn));
smc_pt2=smc_clc2+(smc_pt1>>smc_dn);
smc_new=*((int *)&smc_pt2+1);
}
/* new output value
*/
This 2nd order Lowpass filter will work in the following manner:
response
12,000
140
120
100
80
10,000
8,000
6,000
60
40
20
0
-20 0
-40
pt1
4,000
pt2
2,000
0 time 50
100
150
200
250
required physical values
velo.
a_norm
50
100
150
200 time 250
Therefore, we have to use a simple acceleration and velocity clipper to support the 2nd order
low-pass filter.
void
smc_avclip(void) {
/* limiting to the given physical values*/
smc_clc1=(smc_new-smc_old);
/* actual velocity
*/
if ( smc_clc1 < -smc_vmax ) {
/* test for forward move
*/
/* correction, because of velocity violation */
smc_new=smc_old-smc_vmax;
/* set up new velocity
*/
smc_clc1=-smc_vmax;
/* memorise new velocity
*/
*((int *)&smc_pt2+1)=smc_new; /* set up new output value
*/
}
if ( smc_clc1 > smc_vmax ) {
/* test for reverse move
*/
/* correction, because of velocity violation
*/
smc_new=smc_old+smc_vmax;
/* set up new velocity
*/
smc_clc1=smc_vmax;
/* memorise new velocity
*/
*((int *)&smc_pt2+1)=smc_new; /* set up new output value
*/
}
smc_acc=(smc_clc1-smc_velo);
}
/* actual acceleration
if ( smc_acc < -smc_amax ) {
/* test for acceleration
/* correction, because of acceleration violation
smc_clc1=smc_velo-smc_amax;
/* set up new velocity
smc_new=smc_old+smc_clc1;
/* recalculate output value
*((int *)&smc_pt2+1)=smc_new; /* set up new output value
}
if ( smc_acc > smc_amax ) {
/* test for deceleration
/* correction, because of acceleration violation
smc_clc1=smc_velo+smc_amax;
/* set up new velocity
smc_new=smc_old+smc_clc1;
/* recalculate output value
*((int *)&smc_pt2+1)=smc_new; /* set up new output value
}
smc_acc =smc_clc1-smc_velo;
/* memorisation for debugging
smc_velo=smc_clc1;
/* memorisation for next cycle
MCU-AN-300231-E-V12
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*/
*/
*/
*/
*/
*/
*/
*/
*/
*/
*/
*/
*/
© Fujitsu Microelectronics Europe GmbH
Stepper Motor Controller
Chapter 2 Stepper Motor
This sample code is running in a special interrupt service routine, which should be called
every few milliseconds.
__interrupt void irq_stepper_srv (void) { /* background task for motor controlling */
smc_out(smc_new);
/* force the output first, for less delay glitch
*/
smc__lpf();
/* calculate next cycle output value
*/
smc_avclip();
TMCSR1_UF = 0;
/* reset underflow interrupt request flag
*/
}
Let us also assume that a potentiometer is connected to one of the ADC channel. The actual
position of the rotor of potentiometer is converted into a digital data. These digital data are
used as a controlling parameter for displacement of a pointer which is connected to stepper
motor.
/*-------------------------------------------------------------------*/
void adc_init(void)
{
DDR05_D0 = 0;
ADER1
= 0x01;
ADECR
= 0x00;
ADCS_MD = 0x01;
ADCS_STS = 0x00;
ADSR_ST = 0x06;
ADSR_CT = 0x05;
return;
}
/* P05_0
*/
/*
/*
/*
/*
*/
*/
*/
*/
Select single mode 2
Select software trigger
Sampling time 3us @ 16Mhz
Sampling time 8.3us @ 16Mhz
/*-------------------------------------------------------------------*/
int adc_sample(int chn)
{
int
i,y;
ADSR_ANS = chn;
ADSR_ANE = chn;
y=0;
while ((ADCSH & 0x80) != 0);
for (i=0; i<4; i++)
{
ADCSH=0x82;
while ((ADCSH & 0x80) != 0);
y=y+ADCR;
}
return (y);
}
/*-------------------------------------------------------------------*/
void smc_init(unsigned int x) /* set up all neccesary CPU resources
{
/* initialise cpu output port for the motor */
DDR10=0xFF;
/* assign pins as output
PHDR10 = 0xFF;
PWEC4 = 0x03;
/* initialise low pass filters
*/
smc_inp=0;
/* clear target position
*/
smc_pt1=0; smc_pt2=0; /* clear actual position
smc_new=0; smc_old=0; /* clear actual outputs
/* initialise variables for physical limits */
smc_dn= 4;
/* set up damping grade
smc_vmax=100;
/* set up velocity limit
smc_amax= 5;
/* set up acceleration limit
/* initialise reload timer 1
*/
TMRLR1 = x/2;
/* set reload value in [us]
TMCSR1 = 0x81B;
/* prescaler 2us at 16MHz
}
© Fujitsu Microelectronics Europe GmbH
- 11 -
*/
*/
*/
*/
*/
*/
*/
*/
*/
MCU-AN-300231-E-V12
Stepper Motor Controller
Chapter 2 Stepper Motor
#define
#define
#define
#define
#define
PWC
PWCA
PWCB
PWSA
PWSB
PWC4
PWC14
PWC24
PWS14
PWS24
/*----------- Global Variables -------------------------------------*/
long
int
smc_pt1,
smc_inp,
int
smc_dn,
smc_pt2, smc_clc1, smc_clc2;
smc_new, smc_old, smc_velo,
smc_acc;
smc_vmax, smc_amax;
unsigned int count;
/*------------------------------------------------------------------*/
/* main program :
*/
/*------------------------------------------------------------------*/
void main(void)
{
long
tm, delay;
unsigned char i = 0;
/* this is the MAIN program
*/
/* for support timing control
*/
InitIrqLevels();
__set_il(7);
/* init IRQ Controller
/* allow all levels
*/
*/
adc_init();
smc_init(170);
DDR09 = 0xFF;
/* init Data acquirement
/* Background support x us
*/
*/
{
}
for (smc_inp = 0xD000; smc_inp > 0; smc_inp--)
smc_out(smc_inp);
for (delay=0; delay < 20; delay++)
__asm("\tNOP");
__EI();
/* global enable interrupts
*/
while(1)
{
/* for ever
*/
}
for (tm=3000; tm>0; tm--);
smc_inp = adc_sample(8) * 6;
PDR09 = ADCRL;
/* wait time
*/
/*Show some thing on LED
*/
}
Above example is prepared for SK-96380-120PMT board.
The appropriate output lines of the stepper motor controller are assigned to high power
output stages, which have the capability to drive up to 30 mA, so that small stepper motors
can be driven in direct manner, and bigger ones can be driven easily by connecting a power
bridge to these pins.
MCU-AN-300231-E-V12
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© Fujitsu Microelectronics Europe GmbH
Stepper Motor Controller
Chapter 3 Appendix
3 Appendix
3.1
Figures
Figure 1: Replacement circuit for Stepper Motor .................................................................... 6
Figure 2: Torque Moment calculation ..................................................................................... 6
Figure 3: Without filter, with 1st order LP filter, and with 2nd order LP filter............................ 7
© Fujitsu Microelectronics Europe GmbH
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Stepper Motor Controller
Chapter 4 Additional Information
4 Additional Information
Information about FUJITSU Microcontrollers can be found on the following Internet page:
http://mcu.emea.fujitsu.com/
The software examples related to this application note is:
96380_SMC
It can be found on the following Internet page:
http://mcu.emea.fujitsu.com/mcu_product/mcu_all_software.htm
MCU-AN-300231-E-V12
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© Fujitsu Microelectronics Europe GmbH