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I'm surprised, given the number of embedded applications involving
motor control or data capture, that almost no micros out there support quadrature input. On our products, we use Xilinx FPGA's that provide 8 sets of quadrature input and handle all the accumulation, etc. However, on small footprint boards, with a simple task, it would be very desirable to lose the Xilinx and just read quadrature directly. Even just one pair of quadrature inputs would be fine. Has anyone out there solved this problem? Thanks, Paul Johnson Lynx Robotics 8125 Lankershim Blvd. North Hollywood, CA 91605 Voice: (818) 252-7890 FAX: (818) 252-7892 |
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Quadrature Inputs
Started by ●March 8, 2003
Reply by ●March 8, 20032003-03-08
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"Paul Johnson" <> wrote: >I'm surprised, given the number of embedded applications involving motor >control or data capture, that almost no micros out there support quadrature >input. On our products, we use Xilinx FPGA's that provide 8 sets of Ack, that's bad. [...] >Has anyone out there solved this problem? Do you know the LS7183 from www.lsicsi.com ? It seems you could count the up and down pulses with HC12 pulse counters. I already used a small, cheap PIC for this task, these days I would use a HC08. Oliver -- Oliver Betz, Muenchen |
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Reply by ●March 8, 20032003-03-08
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Hi Paul, yes, the quadrature input is important and rare. But there is one optimal solution - go to see the Motorola Hybrid solution - DSP56F800 family. http://e-www.motorola.com/webapp/sps/site/taxonomy.jsp?nodeIdM95961783629 2 or go direct to DSP56F803 http://e-www.motorola.com/webapp/sps/site/prod_summary.jsp?code=DSP56F803&no deId27956292 Many information and tools on the Motor Control you can find at http://e-www.motorola.com/webapp/sps/site/homepage.jsp?nodeIdnQXG Regards Jiri > ----- Original Message ----- > From: "Paul Johnson" <> > To: <> > Sent: Saturday, March 08, 2003 5:28 PM > Subject: [68HC12] Quadrature Inputs > > I'm surprised, given the number of embedded applications involving motor > > control or data capture, that almost no micros out there support > quadrature > > input. On our products, we use Xilinx FPGA's that provide 8 sets of > > quadrature input and handle all the accumulation, etc. > > > > However, on small footprint boards, with a simple task, it would be very > > desirable to lose the Xilinx and just read quadrature directly. Even just > > one pair of quadrature inputs would be fine. > > > > Has anyone out there solved this problem? > > > > Thanks, > > > > Paul Johnson > > Lynx Robotics > > 8125 Lankershim Blvd. > > North Hollywood, CA 91605 > > Voice: (818) 252-7890 > > FAX: (818) 252-7892 > > > > > > > > -------------------- > > > > > > > > ">http://docs.yahoo.com/info/terms/ > > > > > > > |
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Reply by ●March 8, 20032003-03-08
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Don't forget the MC68332 provides quadrature inputs via the TPU. But I
am sure since the original poster is looking for 'HC12, small footprint soutions, even the '332 may be too big a stretch for him but not as severe as going to DSP chips. Also, keep in mind that various vendors make encoder chips. HP and Gailel come to mind. Check also Nat Semi. Bob Smith --- Avoid computer viruses, Practice safe hex --- -- Specializing in small, cost effective embedded control systems -- http://www.smithmachineworks.com/embedprod.html Robert L. (Bob) Smith Smith Machine Works, Inc. 9900 Lumlay Road Richmond, VA 23236 804/745-1065 ----- Original Message ----- From: "Jiri Gutman" <> To: <> Sent: Saturday, March 08, 2003 3:12 PM Subject: Re: [68HC12] Quadrature Inputs > > Hi Paul, > > yes, the quadrature input is important and rare. But there is one optimal > solution - go to see the Motorola Hybrid solution - DSP56F800 family. http://e-www.motorola.com/webapp/sps/site/taxonomy.jsp?nodeIdM95961783629 > 2 > or go direct to DSP56F803 http://e-www.motorola.com/webapp/sps/site/prod_summary.jsp?code=DSP56F803&no > deId27956292 > > Many information and tools on the Motor Control you can find at > http://e-www.motorola.com/webapp/sps/site/homepage.jsp?nodeIdnQXG > > Regards > Jiri > > ----- Original Message ----- > > From: "Paul Johnson" <> > > To: <> > > Sent: Saturday, March 08, 2003 5:28 PM > > Subject: [68HC12] Quadrature Inputs > > > > > > > I'm surprised, given the number of embedded applications involving motor > > > control or data capture, that almost no micros out there support > > quadrature > > > input. On our products, we use Xilinx FPGA's that provide 8 sets of > > > quadrature input and handle all the accumulation, etc. > > > > > > However, on small footprint boards, with a simple task, it would be very > > > desirable to lose the Xilinx and just read quadrature directly. Even > just > > > one pair of quadrature inputs would be fine. > > > > > > Has anyone out there solved this problem? > > > > > > Thanks, > > > > > > Paul Johnson > > > Lynx Robotics > > > 8125 Lankershim Blvd. > > > North Hollywood, CA 91605 > > > Voice: (818) 252-7890 > > > FAX: (818) 252-7892 > > > > > > > > > > > > -------------------- > > > > > > > > > > > > ">http://docs.yahoo.com/info/terms/ > > > > > > > > > > > > -------------------- > > ">http://docs.yahoo.com/info/terms/ > |
Reply by ●March 8, 20032003-03-08
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> >I'm surprised, given the number of embedded applications
involving motor > >control or data capture, that almost no micros out there support > quadrature > >input. On our products, we use Xilinx FPGA's that provide 8 sets of > > Ack, that's bad. I'm sorry, Oliver, I don't know what you mean. Do you mean that it's bad that we're using Xilinx's or that there are no micros out there with quadrature, or something different altogether? > >Has anyone out there solved this problem? > > Do you know the LS7183 from www.lsicsi.com ? It seems you could count > the up and down pulses with HC12 pulse counters. I didn't, and thanks for the reference. However the reason for quadrature is that it's so much more noise immune than clock and direction or dual clock. Still, on a small board, close to the micro, this might not be a problem. > I already used a small, cheap PIC for this task, these days I would > use a HC08. Yes, precisely, I am looking to do it with a PIC. I was hoping there was a solution out there so that I would not have to reinvent the wheel. Ideally, I would like a parallel interface to off-board accumulators. Regards, Paul |
Reply by ●March 8, 20032003-03-08
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Hi Jiri, I did find these chips, but they are quite a bit larger and more expensive than this little board requires. Most of the resources would be wasted as well. They do look like great chips for larger designs. You would think that some of the high-end PIC's, with their focus on motor control, would have addressed this issue, but apparently not. Regards, Paul > -----Original Message----- > From: Jiri Gutman [mailto:] > Sent: Saturday, March 08, 2003 12:13 PM > To: > Subject: Re: [68HC12] Quadrature Inputs > > Hi Paul, > > yes, the quadrature input is important and rare. But there is one optimal > solution - go to see the Motorola Hybrid solution - DSP56F800 family. > > http://e-www.motorola.com/webapp/sps/site/taxonomy.jsp?nodeIdM9 > 5961783629 > 2 > or go direct to DSP56F803 > > http://e-www.motorola.com/webapp/sps/site/prod_summary.jsp?code=DS > P56F803&no > deId27956292 > > Many information and tools on the Motor Control you can find at > http://e-www.motorola.com/webapp/sps/site/homepage.jsp?nodeIdnQXG > > Regards > Jiri > > ----- Original Message ----- > > From: "Paul Johnson" <> > > To: <> > > Sent: Saturday, March 08, 2003 5:28 PM > > Subject: [68HC12] Quadrature Inputs > > > > > > > I'm surprised, given the number of embedded applications > involving motor > > > control or data capture, that almost no micros out there support > > quadrature > > > input. On our products, we use Xilinx FPGA's that provide 8 sets of > > > quadrature input and handle all the accumulation, etc. > > > > > > However, on small footprint boards, with a simple task, it > would be very > > > desirable to lose the Xilinx and just read quadrature directly. Even > just > > > one pair of quadrature inputs would be fine. > > > > > > Has anyone out there solved this problem? > > > > > > Thanks, > > > > > > Paul Johnson > > > Lynx Robotics > > > 8125 Lankershim Blvd. > > > North Hollywood, CA 91605 > > > Voice: (818) 252-7890 > > > FAX: (818) 252-7892 > > > > > > > > > > > > -------------------- > > > > > > > > > > > > ">http://docs.yahoo.com/info/terms/ > > > > > > > > > > > > -------------------- > > ">http://docs.yahoo.com/info/terms/ |
Reply by ●March 9, 20032003-03-09
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In a message dated 3/8/03 8:52:38 PM Eastern Standard Time, writes: > I'm surprised, given the number of embedded applications > involving motor > control or data capture, that almost no micros out there support > quadrature > input. On our products, we use Xilinx FPGA's that provide 8 sets of > quadrature input and handle all the accumulation, etc. > However, on small footprint boards, with a simple task, it > would be very > desirable to lose the Xilinx and just read quadrature directly. Even > just > one pair of quadrature inputs would be fine. > Has anyone out there solved this problem? Just hook one of the encoder lines to an input with edge triggered interrupt, arm for falling edge interrupt (for instance), read other encoder line in handler, inc on hi, dec on lo. |
Reply by ●March 9, 20032003-03-09
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"Paul Johnson" <> wrote: [...] >I'm sorry, Oliver, I don't know what you mean. Do you mean that it's bad I meant that it's bad that uCs seldom have quadrature inputs. [...] >Yes, precisely, I am looking to do it with a PIC. I was hoping there was a >solution out there so that I would not have to reinvent the wheel. Ideally, >I would like a parallel interface to off-board accumulators. It's pretty simple: In a loop: Concatenate the actual two bit encoder information with the saved two bits of the last round. From these 4 Bits you get 16 combinations, forward, backward, no change and illegal (each four times). Use a jump table to increment/decrement the counter (accumulator) or signal an error. Use some kind of handshake to the host if you output parallel data: either a strobe signal triggered by the host, or a "data illegal" bit. With a 20MHz PIC, I got 4,5us cycle time IIRC. Oliver -- Oliver Betz, Muenchen |
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Reply by ●March 9, 20032003-03-09
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wrote: [...] >Just hook one of the encoder lines to an input with edge triggered interrupt, >arm for falling edge interrupt (for instance), read other encoder line in >handler, inc on hi, dec on lo. This doesn't work reliable: if your encoder moves forward and backward, you loose the backward transition. Oliver -- Oliver Betz, Muenchen |
Reply by ●March 9, 20032003-03-09
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> It's pretty simple: > > In a loop: Concatenate the actual two bit encoder information with the > saved two bits of the last round. From these 4 Bits you get 16 > combinations, forward, backward, no change and illegal (each four > times). > > Use a jump table to increment/decrement the counter (accumulator) or > signal an error. > > Use some kind of handshake to the host if you output parallel data: > either a strobe signal triggered by the host, or a "data illegal" bit. > > With a 20MHz PIC, I got 4,5us cycle time IIRC. It sounds like this is a polling approach. I was thinking of doing something similar to what Bob suggested, but attaching Quad-A to an interrupt which triggers on any transition, then checking the value of the other line in the ISR. I suppose that if the encoder was sitting right on a line, however, this might swamp the interrupt input, but I have not commonly seen this with encoders. With low interrupt latency, I would think this would be pretty reliable, no? Paul |
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