Control Stepper Drive if PIC?

[Bomber-eng]

Good morning.
I would like to know how to generate a routine to control a stepper motor drive with the logic of pulses using a PIC18F.
Would someone have some routine to generate these pulses?
I am having difficulties in creating this routine.
I'm using a Geckodrive G203V.

Pleased I need this information as soon as possible....

Thanks for your attention....

[extrapilot]

Much more information is needed here-
Which 18F MCU would be a start... And, what is the target application? Just one drive, or multiple? And do you want to generate the drive data internally (i.e. robot), or is this an intermediate/translator, etc?

Generating a TTL logic pulse from most any 18F part is trivial. All you have to do is set the TRIS for the pins in question to Output, and then toggle the values for the given port (i.e. PORTE.0 = 1, PORTE.0 = 0). You may also have to disable other peripherals on the port(s) in question- depending on the PIC variant and the port.

You can do that in a timer interrupt routine, or just in the main loop, etc. If you have a motor control PIC (2430 etc) then you have access to some native functionality for HBridge driving, which you could probably use with the 203V just in terms of simplifying step frequency and pulse width.

Are you using a high-level compiler? If so, which?

R

[Bomber-eng]

Actually must generate 400 different speeds for the stteper driver.
Every time I work in a pre determined speed. I tried in TIMER_0 generate a table with the frequencies and running, but when you increase the routine of my program this routine change, changing the frequency of work.
I would like to generate pulses to control properly the speed of the step motor using a PIC 18F in any pin if a 20MHz XTAL.
I do not know how to do a routine to generate these pulses to control the GECKODRIVE G203 with accuracy without the PIC is slow.
I`m so sorry about my english.

Thank's

[extrapilot]

Bomber
I dont think I understand your application. If you are saying that you have 1 of 400 defined frequencies to use per job, your only issue is 'how to tell the pic which frequency you want.' The PIC 18F family have some devices that are designed specifically for motor control. I believe the 18F2431 and 18F4431 are the more capable in that family. These have dedicated PWM modules, which simplify the methods of controlling both the period (frequency) and duty cycle of an output, but the module also manages additional pins so that you can manage hbridge or stepper drivers without concern for output faults (i.e. having opposite sides of an HBridge enabled at the same time).

But you can emulate this in code. Generally, the PIC just leverages a timer and an interrupt for this type of application. So you set the timer value to whatever your period needs to be (timer is a function of the Xtal frequency remember). Then when the timer is started, it counts down to 0, and throws an interrupt. Your interrupt modifies the pin state (high to low, etc), resets the timer value, clears the interrupt, and restarts the timer. So, that process will repeat, and the frequency is determined by the timer value you set, and any timer prescalers or postscalers you set.

There is lots of sample code on the Microchip website (forums). It is not difficult to implement, but if you are new to Interrupts, you need to look at some sample code (since there are some specific details regarding clearing flags, disabling interrupts, etc that are not obvious to someone new to it).

Regarding 'how' to set one of 400 frequencies- It seems to me there are a number of options. One would be some serial link (RS232 is easy)- where you just send a command which contains the new timer value to use. There are other options (like a keypad for direct entry of commands, or just sampling a pot via the ADC converted- so you could twist a control dial to change the frequency)- but that would require a little more code to interpret the keypress or ADC values, and to confirm the setting somehow (maybe a serial LCD panel, or some beep code, or 7-segment LED displays, etc). It really just comes down to the application requirement- the PIC can do any of these things with no difficulties.

R

[Bomber-eng]

Good Morning Extrapilot.

I will try to explain better what I want to do.
I would like to generate the pulses to control the speed of Geckodrive G230. I can enable and disable the brake and change direction of spin easily. But I can not generate an exact routine for each speed. Because many frequencies to vary
I am sending two links below to demonstrate the operation of these drives:

http://www.geckodrive.com/upload/Step_motor_basics.pdf
http://www.geckodrive.com/upload/G203V-REV-6-MANUAL.pdf

Each frequency of a square wave below, is a set speed of my step motor:

Frequency(Hz):
0
3,1
6,2
9,4
12,5
15,6
18,7
21,8
25,0
28,1
31,2
34,3
37,4
40,6
43,7
46,8
49,9
53,1
56,2
59,3
62,4
65,5
68,7
71,8
74,9
78,0
81,1
84,3
87,4
90,5
93,6
96,7
99,9
103,0
106,1
109,2
112,3
115,5
118,6
121,7
124,8
127,9
131,1
134,2
137,3
140,4
143,6
146,7
149,8
152,9
156,0
159,2
162,3
165,4
168,5
171,6
174,8
177,9
181,0
184,1
187,2
190,4
193,5
196,6
199,7
202,8
206,0
209,1
212,2
215,3
218,4
221,6
224,7
227,8
230,9
234,1
237,2
240,3
243,4
246,5
249,7
252,8
255,9
259,0
262,1
265,3
268,4
271,5
274,6
277,7
280,9
284,0
287,1
290,2
293,3
296,5
299,6
302,7
305,8
308,9
312,1
315,2
318,3
321,4
324,6
327,7
330,8
333,9
337,0
340,2
343,3
346,4
349,5
352,6
355,8
358,9
362,0
365,1
368,2
371,4
374,5
377,6
380,7
383,8
387,0
390,1
393,2
396,3
399,4
402,6
405,7
408,8
411,9
415,1
418,2
421,3
424,4
427,5
430,7
433,8
436,9
440,0
443,1
446,3
449,4
452,5
455,6
458,7
461,9
465,0
468,1
471,2
474,3
477,5
480,6
483,7
486,8
489,9
493,1
496,2
499,3
502,4
505,6
508,7
511,8
514,9
518,0
521,2
524,3
527,4
530,5
533,6
536,8
539,9
543,0
546,1
549,2
552,4
555,5
558,6
561,7
564,8
568,0
571,1
574,2
577,3
580,4
583,6
586,7
589,8
592,9
596,1
599,2
602,3
605,4
608,5
611,7
614,8
617,9
621,0
624,1
627,3
630,4
633,5
636,6
639,7
642,9
646,0
649,1
652,2
655,3
658,5
661,6
664,7
667,8
670,9
674,1
677,2
680,3
683,4
686,6
689,7
692,8
695,9
699,0
702,2
705,3
708,4
711,5
714,6
717,8
720,9
724,0
727,1
730,2
733,4
736,5
739,6
742,7
745,8
749,0
752,1
755,2
758,3
761,4
764,6
767,7
770,8
773,9
777,1
780,2
783,3
786,4
789,5
792,7
795,8
798,9
802,0
805,1
808,3
811,4
814,5
817,6
820,7
823,9
827,0
830,1
833,2
836,3
839,5
842,6
845,7
848,8
851,9
855,1
858,2
861,3
864,4
867,6
870,7
873,8
876,9
880,0
883,2
886,3
889,4
892,5
895,6
898,8
901,9
905,0
908,1
911,2
914,4
917,5
920,6
923,7
926,8
930,0
933,1
936,2
939,3
942,4
945,6
948,7
951,8
954,9
958,1
961,2
964,3
967,4
970,5
973,7
976,8
979,9
983,0
986,1
989,3
992,4
995,5
998,6
1001,7
1004,9
1008,0
1011,1
1014,2
1017,3
1020,5
1023,6
1026,7
1029,8
1032,9
1036,1
1039,2
1042,3
1045,4
1048,6
1051,7
1054,8
1057,9
1061,0
1064,2
1067,3
1070,4
1073,5
1076,6
1079,8
1082,9
1086,0
1089,1
1092,2
1095,4
1098,5
1101,6
1104,7
1107,8
1111,0
1114,1
1117,2
1120,3
1123,4
1126,6
1129,7
1132,8
1135,9
1139,1
1142,2
1145,3
1148,4
1151,5
1154,7
1157,8
1160,9
1164,0
1167,1
1170,3
1173,4
1176,5
1179,6
1182,7
1185,9
1189,0
1192,1
1195,2
1198,3
1201,5
1204,6
1207,7
1210,8
1213,9
1217,1
1220,2
1223,3
1226,4
1229,5
1232,7
1235,8
1238,9
1242,0
1245,2
1248,3

I am having difficulties in generating these frequencies with the PIC18F4685. Got it?

I`m so sorry about my english.

Thank's one more time.

[extrapilot]

Bomber-
Your English is much better than my Portuguese, so please do not worry about that!

I have several 203V drives here, and am familiar with their workings- great hardware.

If you do not have a transfer function (i.e. an equation that will output the value based on some simple input), then you will need to setup a lookup table. Normally, that is done using a memory array, so that you would have a cell ID and a value (predefined). It could look just like your example data, with the first column being the cell (row) identifier, and the second the value.

So in the array, if you lookup row 18, you will see value '7' stored there. Now, I dont understand how the numbers you defined function- it appears that the first number is just an increment of 3 over the previous, and the second is some value between 0-9. So how this yields 400 frequencies I am not sure.

Regardless, in my example, you can setup an array and then define the appropriate values as constants. Then, you need to determine 'how' you will communicate with the PIC to tell it which row to use for its new frequency. As I mentioned in an earlier message, there are many ways to communicte with a PIC- so that depends on your requirements. Often, RS232 is the most simple, but there are USB-RS232 converter chips from FTDI that make USB very easy to implement. You could also use a native USB-capable PIC (like the 18F4550), but they are memory constrained.

Do you have a development board you are using? Have you selected a compiler? If not, have a look at Mikroelectronica, they have some very functional development boards, and a compiler you can download for free (just has some limits on the size of the code you compile, but should not be a problem for your app, or at least for testing a smaller array table). There is also lots of sample code included, and on the support forums regarding PWM setup, constant arrays, RS232, etc.

Best,
Rob

[Bomber-eng]

Good Morning Rob!

I`m using CCS compiler to do my program. And a dedicate circuit to control a drive.

Could you please pass your e-mail? So I send the source code to which I have done for their better understanding of what I am doing. But there is a slight problem in my source code, the comments are in Portuguese .....

Thanks again for your help and attention.

[extrapilot]

Bomber- sent you a private message with my email and some questions-

[Bomber-eng]

Thank you for your attention and sent an email to you.
Thanks for everything so far.