Fujitsu Microelectronics Europe
Application Note
MCU-AN-300003-E-V11
F²MC-8L/16LX/FR FAMILY
8/16/32-BIT MICROCONTROLLER
ALL SERIES WITH SMC
STEPPERMOTOR CONTROLLING
FOR POINTER APPLICATION
APPLICATION NOTE
STEPPERMOTOR CONTROLLING
for Pointer Application
Revision History
Revision History
Date
27/08/03
07/04/09
Issue
1.0 First draft, JMe / NFl
1.1 Updated Introduction, MHe
This document contains 17 pages.
Abbreviations:
FME
Fujitsu Microelectronics Europe GmbH
MCU
Microcontroller
SMC
Steppermotor Controller
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© Fujitsu Microelectronics Europe GmbH
STEPPERMOTOR CONTROLLING
for Pointer Application
Warranty and Disclaimer
Warranty and Disclaimer
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header files, application examples, target boards, evaluation boards, engineering samples of IC’s
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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.
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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.
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However, this warranty is excluded if the defect has resulted from an accident not attributable
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3.
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NO LIABILITY FOR CONSEQUENTIAL DAMAGES
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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
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STEPPERMOTOR CONTROLLING
for Pointer Application
Contents
Contents
REVISION HISTORY.............................................................................................................. 2
WARRANTY AND DISCLAIMER ........................................................................................... 3
CONTENTS ............................................................................................................................ 4
0 INTRODUCTION................................................................................................................ 5
1 THE PHYSICS ................................................................................................................... 6
1.1
Performing a steppermotor controlling for a pointer application................................ 6
2 STEPPERMOTOR CONTROLLER ................................................................................... 9
2.1
Microcontroller series with Steppermotor Controller ................................................. 9
2.2
Steppermotor Controller Block .................................................................................. 9
2.3
Steppermotor Controller Registers.......................................................................... 10
2.3.1
PWM Control Register .............................................................................. 10
2.3.2
PWM Compare Register ........................................................................... 12
2.3.3
PWM Select Register ................................................................................ 13
3 SOURCE CODES ............................................................................................................ 15
3.1
Lookup table for microstepping ............................................................................... 15
3.2
Low-pass filter ......................................................................................................... 16
3.3
Sample of a interrupt service routine ...................................................................... 17
3.4
Limiting to the given physical values....................................................................... 17
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© Fujitsu Microelectronics Europe GmbH
STEPPERMOTOR CONTROLLING
for Pointer Application
Introduction
0 Introduction
Stepper motors are widely used in printers, automated machine tools, disk drives,
automotive dashboard instrument clusters, and other applications requiring precise motions
using computer control.
To simplify the design effort and reduce the cost of end products that use stepper motors,
Fujitsu offers low-cost 8-, 16-, and 32-bit microcontrollers with integrated stepper motor drive
circuits.
Special logic and high-current drive circuits are required to drive stepper motors. These can
be designed using discrete logic or special interface ICs, which may result in either
increased design complexity or increased end product cost, or both.
A common use for stepper motors is in automotive dashboard instrument clusters. Stepper
motors are used to power the needles or pointers that indicate parameters, such as vehicle
speed or the RPM of the engine. One or more stepper-motor controllers on Fujitsu’s Flash
Microcontroller can be individually programmed to control the speed gauge, the tachometer,
the fuel gauge, and the engine temperature gauge.
This application note describes exemplarily how to control a steppermotor by Fujitsu’s Flash
Microcontroller with SMC-driver for a pointer application. For more detailed information about
the SMC-functionality of a dedicated device, please see the MCU-series related HW-manual
and datasheet.
© Fujitsu Microelectronics Europe GmbH
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STEPPERMOTOR CONTROLLING
for Pointer Application
Chapter 1 The Physics
1 The Physics
This chapter reflects the technical background of steppermotor controlling
1.1
Performing a steppermotor controlling for a pointer application.
Ix
Some of Fujitsu's MCUs carry a steppermotor controller
macro resource. This can easily used for very smooth
movement of a steppermotor as for sample as an indication
application. Therefore the physically characteristics and
properties have to be known really.
N
For operation it maid be useful to have a small introduction,
what's happens with the physics.
S
Iy
Figure 1: Function principle of steppermotor
In this explanation, we will have a simple replacement model for the steppermotor as a
replacement circuitry. It represents the rotor as one bipolar magnet and two coil which are
arranged rectangular to each other as the stator (Figure 1).
Fy
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 preparing of this is done by
adding the single coil components in a geometrical manner to a
constant result (Fig. 2).
Iy
Fr
Ix
To normalise realise this; we use sin & cos components for
each coil. Therefore, with this model, we can position the rotor
in each random position with the same torque moment.
Fx
Figure 2: Torque moment of steppermotor
For a movement, we have to perform a follow up of positions between a Start and a Stop
position. While controlling usual steppermotor as real stepping devices, this is done with a
step-by-step method (Fig. 3).
So, the movement has constant speed while moving. That is not suited for smart movement,
because, if the motor arrives at the stop position it stops than immediately.
ϕ(t)
ϕ(t)
ϕ(t)
ϕ2
ϕ2
ϕ2
ϕ1
ϕ1
ϕ1
Zone B
t
t
Zone A
t
Zone A
Figure 3: Low-pass filter
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STEPPERMOTOR CONTROLLING
for Pointer Application
Chapter 1 The Physics
To improve this, we use a low-pass filter. The low-pass filter solves the problem at the stop
point (Zone B).
Nevertheless, the same problem exists at the starting point. To solve this, we use a second
order low-pass filter.
The 2nd order low-pass filter solves the problem at the start point (Zone A), 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 maximal 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 simple two stage using of a
1st order LP-Filter.
The 1st order LP-Filter can be performed, by a simple mathematical formula like this (Fig. 4).
PT 1i =
Xini + ( PT 1i −1 * n)
n +1
and
PT 2 i =
PT 1i + ( PT 2 i −1 * n)
n +1
[1]
Figure 4: Formula of Low-pass filter
To implement it in a way to become a fast calculation of it, so it is useful to perform
Y1st_new= ((( Y1st_old<<n ) -Y1st_old ) +Xin__new ) >>n
[2]
Y2nd_new= ((( Y2nd_old<<n ) -Y2nd_old ) +Y1st_new ) >>n
[3]
So only two shift operations and two subtractions have to be performed. This saved CPU
Duty cycles.
This operation has to be performed in a given repetitively time. The difference between the
new output value at this time and the last output value at the last time is the velocity. So that
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 by the last
time speed. The result is the actual acceleration. The physically units are as follows:
Vact =
PT 2i − PT 2i −1
t2 − t1
and
aact =
Vi − Vi −1
t 2 − t1
[4]
Or programming slang spoken:
phi_1 - phi_2 = d_phi
there is: t1 - t2 = d_t
velo = d_phi / d_t
acc = ( d_phi1 - d_phi2 ) / ( ( d_t ) * (d_t) ) ; same as dphi² / dt²
© Fujitsu Microelectronics Europe GmbH
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STEPPERMOTOR CONTROLLING
for Pointer Application
Chapter 1 The Physics
To clipping them at a given moment, we have to proof 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 pretty movement of our pointer in this application.
In practical use, the damping value n should in range of 3-6, because of the characteristics
of the 2nd order Low-pass filter.
For sample, we can use lookup tables to cover the line switching at the output pins for the
Steppermotor.
Herewith a sample of an output function for the Steppermotor macro that uses a 128 microstep per quadrant sinus and cosine lookup table. Otherwise, the given pre-set value for this
function is normalised to 256 micro-steps per quadrant. Therefore, we can easily change the
resolution for a given application from 0..7 Bits per quadrant, only by changing the shift
operation for normalising and fetching the sinus / cosine tables with the necessity length.
C oil_A
C oil_B
--> microSteps
256
192
128
CPU_Pin : PWM1Px Æ + Coil_A ( + SIN )
64
CPU_Pin : PWM1Mx Æ - Coil_A ( - SIN )
0
-64 0
256
512
768
1024
CPU_Pin : PWM2Px Æ + Coil_B ( + COS )
CPU_Pin : PWM2Mx Æ + Coil_B ( - COS )
-128
-192
-256
Quadr 0
Quadr 1
Quadr 2
Quadr 3
Figure 5: Output function for the Steppermotor macro
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© Fujitsu Microelectronics Europe GmbH
STEPPERMOTOR CONTROLLING
for Pointer Application
Chapter 2 Steppermotor Controller
2 Steppermotor Controller
This chapter shows the features of Steppermotor Controller
2.1
Microcontroller series with Steppermotor Controller
Fujitsu Microelectronics provides some microcontrollers with integrated SMC-drivers:
16LX
MCU series
Type
SMC
channels
FR
MCU series
Type
SMC
channels
MB90F394
16bit
6ch
MB91F362
32bit
4ch
MB90F427
16bit
4ch
MB91F365
4ch
MB90F428
16bit
4ch
MB91F366
32bit
32bit
4ch
MB90F591
16bit
4ch
MB91F368
32bit
4ch
MB90F594
16bit
4ch
MB91F376
32bit
4ch
MB90F598
16bit
4ch
8L
MCU series
Type
SMC
channels
MB89943
8bit
1ch
MB89945
8bit
1ch
2.2
Steppermotor Controller Block
The mentioned MCU series will be used exemplary to reflect the internal Steppermotor
controller. The Steppermotor controller consists of four motor drivers, the corresponding
selector logic, and two PWM pulse generators.
The four motor drivers have high-current drive
capabilities capability to drive up to 30mA,
and they can be directly connected to the four
ends of two motor coils.
So, that very small steppermotor can be
driven in direct manner, and bigger ones can
be driven by easily connecting a power bridge
to these pins.
Figure 6: Steppermotor output driver
© Fujitsu Microelectronics Europe GmbH
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STEPPERMOTOR CONTROLLING
for Pointer Application
Chapter 2 Steppermotor Controller
The combination of the PWM Pulse Generators and Selector Logic is designed to control the
rotation of the motor.
The Steppermotor controller block is divided into 2 channels to connect the four ends of two
motor coils as described in the following illustration.
Figure 7: Block diagram of Steppermotor Controller
2.3
Steppermotor Controller Registers
The stepping motor controller "n" has the following five types of registers:
• PWM control n register (PWMCn)
• PWM1 compare n register (PWC1n)
• PWM2 compare n register (PWC2n)
• PWM1 select register (PWS1n)
• PWM2 select register (PWS2n)
2.3.1 PWM Control Register
The PWM control register (PWMCn) starts and stops the Steppermotor Controller, controls
the interrupts, and sets the external output pins. Its function is equal to all other SMC
modules.
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© Fujitsu Microelectronics Europe GmbH
STEPPERMOTOR CONTROLLING
for Pointer Application
Chapter 2 Steppermotor Controller
Figure 8: PWM control register
Figure 9: Function of each bit of the PWM control register
© Fujitsu Microelectronics Europe GmbH
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STEPPERMOTOR CONTROLLING
for Pointer Application
Chapter 2 Steppermotor Controller
2.3.2 PWM Compare Register
The PWM1 and 2 compare registers (PWC1n + PWC2n) determine the widths of PWM
pulses. The stored value of "00h" represents the PWM duty of 0% and "FFH" represents the
duty of 99.6%. The two 8-bit compare registers are accessible at any time, however the
modified values are reflected to the pulse width at the end of the current PWM cycle after the
BS bit of the PWM2 Select register is set to "1".
Figure 10: PWM1&2 compare registers
Figure 11: Examples for duty cycle settings
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© Fujitsu Microelectronics Europe GmbH
STEPPERMOTOR CONTROLLING
for Pointer Application
Chapter 2 Steppermotor Controller
2.3.3 PWM Select Register
The PWM1 and PWM2 select registers (PWS1n + PWS2n) can choose between static low,
static high, PWM pulse, or high impedance for the external output pin of the Steppermotor
Controller.
Figure 12: PWM1 select register
Figure 13: Function of each bit of the PWM1 select register
© Fujitsu Microelectronics Europe GmbH
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STEPPERMOTOR CONTROLLING
for Pointer Application
Chapter 2 Steppermotor Controller
Figure 14: PWM2 select register
Figure 15: Function of each bit of the PWM2 select register
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© Fujitsu Microelectronics Europe GmbH
STEPPERMOTOR CONTROLLING
for Pointer Application
Chapter 3 SOURCE CODES
3 SOURCE CODES
This Chapter shows and explains the source code for a pointer application
3.1
Lookup table for microstepping
/* THIS SAMPLE CODE IS PROVIDED AS IS AND IS SUBJECT TO ALTERATIONS. FUJITSU
/* MICROELECTRONICS ACCEPTS NO RESPONSIBILITY OR LIABILITY FOR ANY ERRORS OR
/* ELIGIBILITY FOR ANY PURPOSES.
/*
(C) Fujitsu Microelectronics Europe GmbH
*/
*/
*/
*/
/* 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;
/* some squeeze intermediate memories */
q=((ustp>>8) & 3);
/*
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 */
}
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for Pointer Application
Chapter 3 SOURCE CODES
3.2
Low-pass filter
This output driver routine is hopefully a balanced finish between minimised memory
requirements are clear viewing of coding effects.
Herewith a sample of a 2nd order Low-pass filter interrupt to support the output function for
the Steppermotor.
/* THIS SAMPLE CODE IS PROVIDED AS IS AND IS SUBJECT TO ALTERATIONS. FUJITSU
/* MICROELECTRONICS ACCEPTS NO RESPONSIBILITY OR LIABILITY FOR ANY ERRORS OR
/* ELIGIBILITY FOR ANY PURPOSES.
/*
(C) Fujitsu Microelectronics Europe GmbH
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;
smc_clc1=(smc_clc1>>smc_dn);
smc_clc2=(smc_pt1-(smc_pt1>>smc_dn));
smc_pt1=smc_clc2+smc_clc1;
/* normalise input value */
/* */
/* 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 Low-pass filter will work thru the following manner:
response
12,000
140
120
100
80
60
40
10,000
8,000
6,000
pt1
4,000
pt2
20
0
-20 0
-40
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.
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© Fujitsu Microelectronics Europe GmbH
STEPPERMOTOR CONTROLLING
for Pointer Application
Chapter 3 SOURCE CODES
3.3
Sample of a interrupt service routine
This sample code is running in a special interrupt service routine, which should be called
every few milliseconds.
/* THIS SAMPLE CODE IS PROVIDED AS IS AND IS SUBJECT TO ALTERATIONS. FUJITSU
/* MICROELECTRONICS ACCEPTS NO RESPONSIBILITY OR LIABILITY FOR ANY ERRORS OR
/* ELIGIBILITY FOR ANY PURPOSES.
/*
(C) Fujitsu Microelectronics Europe GmbH
*/
*/
*/
*/
__interrupt void irq_stepper_srv (void) { /* background task for motor controlling
*/
smc_out(smc_new);
/* force the output first, for less delay glitch */
smc__ido();
/* calculate next cycle output value */
smc_avclip();
/* */
TMCSR1_UF = 0; /* reset underflow interrupt request flag */
}
3.4
Limiting to the given physical values
/* THIS SAMPLE CODE IS PROVIDED AS IS AND IS SUBJECT TO ALTERATIONS. FUJITSU
/* MICROELECTRONICS ACCEPTS NO RESPONSIBILITY OR LIABILITY FOR ANY ERRORS OR
/* ELIGIBILITY FOR ANY PURPOSES.
/*
(C) Fujitsu Microelectronics Europe GmbH
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 reward 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 breaking */
/* 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 */
}
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