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"Paul Johnson" <> wrote: [...] >It sounds like this is a polling approach. I was thinking of doing IMHO that's the most reliable way to do it. >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. If you have an encoder with hysteresis, it will only occur if there is mechanical vibration. Do you know whether the encoder used in the application has hysteresis to avoid oscillation under any condition? >With low interrupt latency, I would think this >would be pretty reliable, no? If the condition mentioned above is met... otherwise it's really dangerous! And with a high pulse rate, it will consume lots of CPU power. If you you have a dedicated uC for the decoding, the loop approach is much faster than the interrupt approach. Oliver -- Oliver Betz, Muenchen |
Quadrature Inputs
Started by ●March 8, 2003
Reply by ●March 9, 20032003-03-09
Reply by ●March 9, 20032003-03-09
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Check out the TI TMS340 series. Fixed point DSP. It's pretty much made
for motor control and has quadrature decoding built in. A real fast, cheap (about same as HC12) flash DSP. You'll love the Code Composer IDE - it comes with real books that tell you how to use it, written by technically-competent people whose primary language is English. Same story for the hardware. You'll probably want to code in C. The assembly language is amazing(ly complex). It has two ALUs, one just for address calculations. Modified Harvard architecture. True 16-bit machine. It'll do a MAC in one clock cycle. If I weren't stuck with a legacy product, I'd be using TI. This is all from memory a few years old, so don't quote me. Bob White ----- Original Message ----- From: "Paul Johnson" <> To: <> Sent: Sunday, March 09, 2003 8:16 AM Subject: RE: [68HC12] Quadrature Inputs > 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 -------------------- ">http://docs.yahoo.com/info/terms/ |
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Reply by ●March 9, 20032003-03-09
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"whose primary language is English " LOL, I love that!! wrote: > Check out the TI TMS340 series. Fixed point DSP. It's pretty much > made for > motor control and has quadrature decoding built in. A real fast, cheap > (about same as HC12) flash DSP. You'll love the Code Composer IDE - it > comes with real books that tell you how to use it, written by > technically-competent people whose primary language is English. Same > story > for the hardware. You'll probably want to code in C. The assembly > language > is amazing(ly complex). It has two ALUs, one just for address > calculations. > Modified Harvard architecture. True 16-bit machine. It'll do a MAC > in one > clock cycle. If I weren't stuck with a legacy product, I'd be using TI. > This is all from memory a few years old, so don't quote me. > > Bob White > > ----- Original Message ----- > From: "Paul Johnson" <> > To: <> > Sent: Sunday, March 09, 2003 8:16 AM > Subject: RE: [68HC12] Quadrature Inputs > > 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 > > -------------------- > > ">http://docs.yahoo.com/info/terms/ > Yahoo! Groups Sponsor > > <http://ads.x10.com/?bHlhaG9vaG0xLmRhd47239968%3eM$7865.3003379.4374531.2848452/D=egroupweb/S06554205:HM/A82387/R=147239968%3eM$7865.3003379.4374531.2848452/D=egroupweb/S06554205:HM/A82387/R=2" target="_blank" rel="nofollow">http://rd.yahoo.com/M$7865.3003379.4374531.2848452/D=egroupweb/S06554205:HM/A82387/R=0/*http://ads.x10.com/?bHlhaG9vaG0xLmRhd47239968%3eM$7865.3003379.4374531.2848452/D=egroupweb/S06554205:HM/A82387/R=147239968%3eM$7865.3003379.4374531.2848452/D=egroupweb/S06554205:HM/A82387/R=2 > > -------------------- > > ">http://docs.yahoo.com/info/terms/>. |
Reply by ●March 9, 20032003-03-09
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The only things I could find on TI's website with TMS340 in the part
number were 32 bit graphics processors, all but one of which are listed as obsolete. I didn't find anything like what you are describing. Could it be a different series? Thanks, Paul > -----Original Message----- > From: Bob White [mailto:] > Sent: Sunday, March 09, 2003 12:02 PM > To: > Subject: Re: [68HC12] Quadrature Inputs > Check out the TI TMS340 series. Fixed point DSP. It's pretty > much made for > motor control and has quadrature decoding built in. A real fast, cheap > (about same as HC12) flash DSP. You'll love the Code Composer IDE - it > comes with real books that tell you how to use it, written by > technically-competent people whose primary language is English. > Same story > for the hardware. You'll probably want to code in C. The > assembly language > is amazing(ly complex). It has two ALUs, one just for address > calculations. > Modified Harvard architecture. True 16-bit machine. It'll do a > MAC in one > clock cycle. If I weren't stuck with a legacy product, I'd be using TI. > This is all from memory a few years old, so don't quote me. > > Bob White > > ----- Original Message ----- > From: "Paul Johnson" <> > To: <> > Sent: Sunday, March 09, 2003 8:16 AM > Subject: RE: [68HC12] Quadrature Inputs > > 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 > > -------------------- > > ">http://docs.yahoo.com/info/terms/ > > -------------------- > > ">http://docs.yahoo.com/info/terms/ |
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Reply by ●March 9, 20032003-03-09
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Never mind, I think I found it. It's in the 320 series, but it matches
the description you give. We'll be investigating this chip this week. Thanks, Paul > -----Original Message----- > From: Paul Johnson [mailto:] > Sent: Sunday, March 09, 2003 6:10 PM > To: > Subject: RE: [68HC12] Quadrature Inputs > The only things I could find on TI's website with TMS340 in the > part number > were 32 bit graphics processors, all but one of which are listed as > obsolete. I didn't find anything like what you are describing. > > Could it be a different series? > > Thanks, > > Paul > > > -----Original Message----- > > From: Bob White [mailto:] > > Sent: Sunday, March 09, 2003 12:02 PM > > To: > > Subject: Re: [68HC12] Quadrature Inputs > > > > > > Check out the TI TMS340 series. Fixed point DSP. It's pretty > > much made for > > motor control and has quadrature decoding built in. A real fast, cheap > > (about same as HC12) flash DSP. You'll love the Code Composer IDE - it > > comes with real books that tell you how to use it, written by > > technically-competent people whose primary language is English. > > Same story > > for the hardware. You'll probably want to code in C. The > > assembly language > > is amazing(ly complex). It has two ALUs, one just for address > > calculations. > > Modified Harvard architecture. True 16-bit machine. It'll do a > > MAC in one > > clock cycle. If I weren't stuck with a legacy product, I'd be using TI. > > This is all from memory a few years old, so don't quote me. > > > > Bob White > > > > ----- Original Message ----- > > From: "Paul Johnson" <> > > To: <> > > Sent: Sunday, March 09, 2003 8:16 AM > > Subject: RE: [68HC12] Quadrature Inputs > > > > > > > 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 > > > > > > > > -------------------- > > > > > > > > ">http://docs.yahoo.com/info/terms/ > -------------------- > > ">http://docs.yahoo.com/info/terms/ -------------------- ">http://docs.yahoo.com/info/terms/ |
Reply by ●March 9, 20032003-03-09
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Depending on the edge rates, you can either use interrupts off the appropriate port pins (if they are slow enough) or there are nice single-chip solutions like the HCTL2000 from Agilent (the old HP). Or, your favorite EPLD or FPGA if you need a lot of them... /s/jar http://www.mtritter.org EMAIL DISCLAIMER Please Note: The information contained in this message may be privileged and confidential, protected from disclosure, and/or intended only for the use of the individual or entity named above. If the reader of this message is not the intended recipient, or an employee or agent responsible for delivering this message to the intended recipient, you are hereby notified that any disclosure, distribution, copying or other dissemination of this communication is strictly prohibited. If you received this communication in error, please immediately reply to the sender, delete the message and destroy all copies of it. Thank You |
Reply by ●March 10, 20032003-03-10
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Also look at MC68HC16, and MPC500 series these have the TPU that can be
configured for Quadrature detection. What does the HCS12H have perhaps that can do quadrature as well? Andrew Lohmann AIIE Design Engineer Bellingham + Stanley Ltd. Longfield Road, Tunbridge Wells, Kent, TN2 3EY, England. Tel: +44 (0) 1892 500400 Fax: +44 (0) 1892 543115 Website: www.bs-ltd.com ----- Original Message ----- From: Ritter, Alan To: ' Sent: Monday, March 10, 2003 3:50 AM Subject: RE: [68HC12] Quadrature Inputs Depending on the edge rates, you can either use interrupts off the appropriate port pins (if they are slow enough) or there are nice single-chip solutions like the HCTL2000 from Agilent (the old HP). Or, your favorite EPLD or FPGA if you need a lot of them... /s/jar http://www.mtritter.org EMAIL DISCLAIMER Please Note: The information contained in this message may be privileged and confidential, protected from disclosure, and/or intended only for the use of the individual or entity named above. If the reader of this message is not the intended recipient, or an employee or agent responsible for delivering this message to the intended recipient, you are hereby notified that any disclosure, distribution, copying or other dissemination of this communication is strictly prohibited. If you received this communication in error, please immediately reply to the sender, delete the message and destroy all copies of it. Thank You -------------------- --- Email Disclaimer --- Internet communications are not secure and therefore Bellingham + Stanley Ltd does not accept legal responsibility for the contents of this message. Any views or opinions presented are solely those of the author and do not necessarily represent those of Bellingham + Stanley Ltd unless otherwise specifically stated. If this message is received by anyone other than the addressee, please notify the sender and then delete the message and any attachments from your computer. --- End --- --- Email Disclaimer --- Internet communications are not secure and therefore Bellingham + Stanley Ltd does not accept legal responsibility for the contents of this message. Any views or opinions presented are solely those of the author and do not necessarily represent those of Bellingham + Stanley Ltd unless otherwise specifically stated. If this message is received by anyone other than the addressee, please notify the sender and then delete the message and any attachments from your computer. --- End --- |
Reply by ●March 10, 20032003-03-10
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Hi, Some years back i did a winch controle wire out and speed for a ship trawl warps. I used a 8051 then and did it as follows: Used a D-type latch 74HCT74 with PRE/CLR connected to Vcc. The one phase input connected to "D" input and the Q connected to a port pin (the /Q not used). The other phase goes to the Clock pin on the D type latch and at the same time to a interrupt line on the processor. Both phases should be buffered with hysterieses , barrier diode, caps etc. IT WORKS AS FOLLOW:......78>)) The the one phase feeding into D and the other into the clock input of the 74HCT74 we obtain the phase leading or lagging so we can figure out what direction the shaft turns. The Q output will indicate the direction "0" one direction "1" other direction. The one phase feeding straight into the CPU has to functions. First, it is used to measure time intervals for measuring shaft speed. Second, it is used as a pulse counter to measure length of wire. So we end up with 3 neat variables, speed wire out and direction!! Now just for the interrest of it. Do not place your sensors on the wire drum!!! Place your sensors on a roler that has a consistant diameter to the cable spooling............. Frank van der Merwe(the info is free....) ----- Original Message ----- From: <> To: <> Sent: Saturday, March 08, 2003 8:04 PM Subject: Re: [68HC12] Quadrature Inputs > 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. > > > -------------------- > > ">http://docs.yahoo.com/info/terms/ |
Reply by ●March 10, 20032003-03-10
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For PIC solution see JR Kerr's website jrkerr.com. They offer PIC-ENC in a 20 pin 16C54. I've used this inconjunction with their PIC-SERVO to implement PID motor control. Nick > -----Original Message----- > From: Paul Johnson [mailto:] > Sent: Saturday, March 08, 2003 8:47 PM > To: > Subject: RE: [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 > > > > 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 > ------------------------ Yahoo! Groups Sponsor > ---------------------~--> > Get 128 Bit SSL Encryption! > http://us.click.yahoo.com/xaxhjB/hdqFAA/xGHJAA/dN_tlB/TM > -------------------------- > -------~-> > > -------------------- > > ">http://docs.yahoo.com/info/terms/ |
Reply by ●March 10, 20032003-03-10
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This has some limitations: Noise susceptibility At high motor speeds can use all the controller's bandwidth Doesn't use the 4x advantage of quadrature encoding Nick > -----Original Message----- > From: [mailto:] > Sent: Saturday, March 08, 2003 11:05 PM > To: > Subject: Re: [68HC12] Quadrature Inputs > 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. > > ------------------------ Yahoo! Groups Sponsor > ---------------------~--> > Get 128 Bit SSL Encryption! > http://us.click.yahoo.com/xaxhjB/hdqFAA/xGHJAA/dN_tlB/TM > -------------------------- > -------~-> > > -------------------- > > ">http://docs.yahoo.com/info/terms/ |
