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aaaaamartin
Joined: 17 Apr 2005
Posts: 39
Location: Germany Stuttgart
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| Help with QEI |
 Posted: Tue Oct 11, 2005 11:11 am |
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Hello,
I want to use the built in QEI on a 18F4431 with a quad encoder.
No its not the one you mount to the motorshaft, its one for manual data entry. However this is much slower, i think why not use the QEI for that as wel.
The problem is, I can not figur out why the interrupts happen more than once. And this is also different right after direction changes and whether I rotate cw or ccw.
Is this normal behaviour ?
Heres is some code if one has an encoder to try out.
| Code: |
#ZERO_RAM
#include <18F4431.h>
#fuses NOWDT, H4, NOPUT, NOPROTECT, NOBROWNOUT, NOLVP, NOCPD, NOWRT, NODEBUG, SSP_RC
#use delay(clock=40000000)
#use rs232 (baud=38400, xmit=PIN_C6, rcv=PIN_C7, disable_ints)
#BYTE QEICON=0xFB6 // quadrature configure
#bit QEICONDIR=0xFB6.5
#BYTE DFLTCON=0xF60 // quadrature noise filter configure
#BYTE CAP2BUFL=0xF66 // position counter
#BYTE CAP2BUFH=0xF67
#BYTE CAP3BUFL=0xF64 //max count
#BYTE CAP3BUFH=0xF65
int drcnt;
int qeicnt;
#int_IC3DR
void ic3dr_interrupt (void) {
output_toggle (PIN_D0);
drcnt ++;
}
#int_IC2QEI
void ic2qei_interrupt (void) {
output_toggle (PIN_D1);
qeicnt++;
}
void main (void) {
enable_interrupts (INT_IC2QEI); // interrupt on maxcount or underflow
enable_interrupts (INT_IC3DR);
enable_interrupts (GLOBAL);
QEICON=0b00011000; // quad in x4 mode, resettable by maxcount
DFLTCON=49; // noise filter on QEA, QEB,, 1:2 clock
CAP3BUFL=0x0F; // set max count
CAP3BUFH=0x00;
CAP2BUFL=0x00; // reset count
CAP2BUFH=0x00;
while (1) {
printf("\rCAP2:%X-%X ; CAP3:%X-%X ; QEICON:%X ;qeicnt %03u ; drcnt: %03u", CAP2BUFH, CAP2BUFL, CAP3BUFH, CAP3BUFL, QEICON, qeicnt, drcnt);
delay_ms (50);
}
}
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Thanks you, Martin |
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kender
Joined: 09 Aug 2004
Posts: 768
Location: Silicon Valley
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| $0.02 hardware hypothesis |
| Posted: Tue Oct 11, 2005 5:20 pm |
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Are you using a mechanical encoder or an optical one?
Mechanical encoders have the bouncing problem, because they have mechanical switches. If you want to connect a mechanical encoder to the interupt, you need to debounce all of its outputs. There is a sample circuit at the bottom of page 1 of this datasheet: http://www.bourns.com/pdf/ecw1j.pdf
Optical encoders don't have this problem. |
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aaaaamartin
Joined: 17 Apr 2005
Posts: 39
Location: Germany Stuttgart
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| Posted: Wed Oct 12, 2005 3:51 am |
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It's a mechanical encoder by ALPS.
I dont't think it's a debounce problem.
It's working in both directions, and in all cases counts one time,
except I change direction from cw to ccw, then it counts -3 right after the change. Then it coutns -1 again, as it should.
Martin |
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sseidman
Joined: 14 Mar 2005
Posts: 159
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| Posted: Wed Oct 12, 2005 8:29 am |
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| aaaaamartin wrote: | It's a mechanical encoder by ALPS.
I dont't think it's a debounce problem.
It's working in both directions, and in all cases counts one time,
except I change direction from cw to ccw, then it counts -3 right after the change. Then it coutns -1 again, as it should.
Martin |
I'd still start by debouncing. The noise filters on the QEI might take care of all the problems, except during the direction change you describe.
Scott |
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aaaaamartin
Joined: 17 Apr 2005
Posts: 39
Location: Germany Stuttgart
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| Posted: Wed Oct 12, 2005 8:54 am |
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I'll do a software workarround.
If anyone else thinks this abnormal .....
Thanks
Martin |
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