1 // Demo program for stepper motor control with linear ramps
2 // Hardware: PIC18F252, L6219
3 #include "18F252.h"
4
5 // PIC18F252 SFRs
6 #byte TRISC = 0xf94
7 #byte T3CON = 0xfb1
8 #byte CCP2CON = 0xfba
9 #byte CCPR2L = 0xfbb
10 #byte CCPR2H = 0xfbc
11 #byte CCP1CON = 0xfbd
12 #byte CCPR1L = 0xfbe
13 #byte CCPR1H = 0xfbf
14 #byte T1CON = 0xfcd
15 #byte TMR1L = 0xfce
16 #byte TMR1H = 0xfcf
17 #bit TMR1ON = T1CON.0
18
19 // 1st step=50ms; max speed=120rpm (based on 1MHz timer, 1.8deg steps)
20 #define C0 50000
21 #define C_MIN 2500
22
23 // ramp state-machine states
24 #define ramp_idle 0
25 #define ramp_up 1
26 #define ramp_max 2
27 #define ramp_down 3
28 #define ramp_last 4
29
30 // Types: int8,int16,int32=8,16,32bit integers, unsigned by default
31 int8 ramp_sts=ramp_idle;
32 signed int16 motor_pos = 0; // absolute step number
33 signed int16 pos_inc=0; // motor_pos increment
34 int16 phase=0; // ccpPhase[phase_ix]
35 int8 phase_ix=0; // index to ccpPhase[]
36 int8 phase_inc; // phase_ix increment
37 int8 run_flg; // true while motor is running
38 int16 ccpr; // copy of CCPR1&2
39 int16 c; // integer delay count
40 int16 step_no; // progress of move
41 int16 step_down; // start of down-ramp
42 int16 move; // total steps to move
43 int16 midpt; // midpoint of move
44 int32 c32; // 24.8 fixed point delay count
45 signed int16 denom; // 4.n+1 in ramp algo
46
47 // Config data to make CCP1&2 generate quadrature sequence on PHASE pins
48 // Action on CCP match: 8=set+irq; 9=clear+irq
49 int16 const ccpPhase[] = {0x909, 0x908, 0x808, 0x809}; // 00,01,11,10
50
current_on()51 void current_on(){/* code as needed */} // motor drive current
current_off()52 void current_off(){/* code as needed */} // reduce to holding value
53
54 // compiler-specific ISR declaration
55 #INT_CCP1
isr_motor_step()56 void isr_motor_step()
57 { // CCP1 match -> step pulse + IRQ
58 ccpr += c; // next comparator value: add step delay count
59 switch (ramp_sts)
60 {
61 case ramp_up: // accel
62 if (step_no==midpt)
63 { // midpoint: decel
64 ramp_sts = ramp_down;
65 denom = ((step_no - move)<<2)+1;
66 if (!(move & 1))
67 { // even move: repeat last delay before decel
68 denom +=4;
69 break;
70 }
71 }
72 // no break: share code for ramp algo
73 case ramp_down: // decel
74 if (step_no == move-1)
75 { // next irq is cleanup (no step)
76 ramp_sts = ramp_last;
77 break;
78 }
79 denom+=4;
80 c32 -= (c32<<1)/denom; // ramp algorithm
81 // beware confict with foreground code if long div not reentrant
82 c = (c32+128)>>8; // round 24.8format->int16
83 if (c <= C_MIN)
84 { // go to constant speed
85 ramp_sts = ramp_max;
86 step_down = move - step_no;
87 c = C_MIN;
88 break;
89 }
90 break;
91 case ramp_max: // constant speed
92 if (step_no == step_down)
93 { // start decel
94 ramp_sts = ramp_down;
95 denom = ((step_no - move)<<2)+5;
96 }
97 break;
98 default: // last step: cleanup
99 ramp_sts = ramp_idle;
100 current_off(); // reduce motor current to holding value
101 disable_interrupts(INT_CCP1);
102 run_flg = FALSE; // move complete
103 break;
104 } // switch (ramp_sts)
105 if (ramp_sts!=ramp_idle)
106 {
107 motor_pos += pos_inc;
108 ++step_no;
109 CCPR2H = CCPR1H = (ccpr >> 8); // timer value at next CCP match
110 CCPR2L = CCPR1L = (ccpr & 0xff);
111 if (ramp_sts!=ramp_last) // else repeat last action: no step
112 phase_ix = (phase_ix + phase_inc) & 3;
113 phase = ccpPhase[phase_ix];
114 CCP1CON = phase & 0xff; // set CCP action on next match
115 CCP2CON = phase >> 8;
116 } // if (ramp_sts != ramp_idle)
117 } // isr_motor_step()
118
motor_run(short pos_new)119 void motor_run(short pos_new)
120 { // set up to drive motor to pos_new (absolute step#)
121 if (pos_new < motor_pos) // get direction & #steps
122 {
123 move = motor_pos-pos_new;
124 pos_inc = -1;
125 phase_inc = 0xff;
126 }
127 else if (pos_new != motor_pos)
128 {
129 move = pos_new-motor_pos;
130 pos_inc = 1;
131 phase_inc = 1;
132 }
133 else return; // already there
134 midpt = (move-1)>>1;
135 c = C0;
136 c32 = c<<8; // keep c in 24.8 fixed-point format for ramp calcs
137 step_no = 0; // step counter
138 denom = 1; // 4.n+1, n=0
139 ramp_sts = ramp_up; // start ramp state-machine
140 run_flg = TRUE;
141 TMR1ON = 0; // stop timer1;
142 ccpr = make16(TMR1H,TMR1L); // 16bit value of Timer1
143 ccpr += 1000; // 1st step + irq 1ms after timer1 restart
144 CCPR2H = CCPR1H = (ccpr >> 8);
145 CCPR2L = CCPR1L = (ccpr & 0xff);
146 phase_ix = (phase_ix + phase_inc) & 3;
147 phase = ccpPhase[phase_ix];
148 CCP1CON = phase & 0xff; // sets action on match
149 CCP2CON = phase >> 8;
150 current_on(); // current in motor windings
151 enable_interrupts(INT_CCP1);
152 TMR1ON=1; // restart timer1;
153 } // motor_run()
154
155
initialize()156 void initialize()
157 {
158 disable_interrupts(GLOBAL);
159 disable_interrupts(INT_CCP1);
160 disable_interrupts(INT_CCP2);
161 output_c(0);
162 set_tris_c(0);
163 T3CON = 0;
164 T1CON = 0x35;
165 enable_interrupts(GLOBAL);
166 } // initialize()
167
main()168 void main()
169 {
170 initialize();
171 while (1)
172 { // repeat 5 revs forward & back
173 motor_run(1000);
174 while (run_flg);
175 motor_run(0);
176 while (run_flg);
177 }
178 } // main()
179 // end of file motor.c
180