Apin with the counter modules

Comments

• Jack Buffington Posts: 115

  2010-02-22 22:47 edited 2010-02-22 22:47

  I have also tried this
  
  

                mov       tempa,ctraData2
                shl       tempa, #23
                mov       tempb,#1
                shl       tempb,#9
                add       tempa,tempb
                add       tempa,#0                ' this is the pin number
                mov       ctra,tempa
  
  
  ... later in the program:
  ctraData2     long      %00100000   
  
  

  
  
  
  which should be the equivalent to the spin command:
  

  ctra    := %00100_000 << 23 + 1 << 9 + 0  
  
  

  
  
  
  With Spin I can set the pin to whatever I want but I would really rather not waste a whole cog on this. I would rather set up the counter at the beginning of another assembly language program and forget about it.
• Phil Pilgrim (PhiPi) Posts: 23,514

  2010-02-22 22:47 edited 2010-02-22 22:47

  Your IOPins value ($11111111) sets only every fourth pin as an output.
  
  -Phil
• Bean Posts: 8,129

  2010-02-22 23:38 edited 2010-02-22 23:38

  Phil Pilgrim (PhiPi) said...
  Your IOPins value ($11111111) sets only every fourth pin as an output.
  
  -Phil

  I think he meant to use $FFFFFFFF that would make all pins outputs.
  
  Bean
  
  
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  Use BASIC on the Propeller with the speed of assembly language.
  
  PropBASIC thread http://forums.parallax.com/showthread.php?p=867134
  
  March 2010 Nuts and Volts article·http://www.parallax.com/Portals/0/Downloads/docs/cols/nv/prop/col/nvp5.pdf
  ·
• Ariba Posts: 2,694

  2010-02-22 23:45 edited 2010-02-22 23:45

  You can write the counter mode like in spin, this makes it more readable.
  And you can use constants from a CON section in PASM for the pin number.
  Then your code will look like this:
  

  CON
    _CLKMODE = XTAL1 + PLL16X
    _XINFREQ = 5_000_000
  
    OutPin = 3
  
  VAR
    long temp
  
  PUB start
    cognew(@counterStart, 0)
    repeat
       temp := 0   
  
  DAT
                org
  counterStart
                mov       dira,PinMask
                mov       ctra,ctraData
                mov       frqa,frqaData
  jPoint        jmp       #jPoint
  
  PinMask       long      1 << OutPin
  ctraData      long      %00100_000 << 23 + 1 << 9 + OutPin
  frqaData      long      $40000000
  
  

  
  
  But your versions will also work if you set the right pins as output(s).
  
  Andy
• Jack Buffington Posts: 115

  2010-02-27 00:56 edited 2010-02-27 00:56

  Yep. It usually is the stupid stuff that gets me. I'm used to working with 8-bit micros and usually set my I/O directions manually in binary so that looked right to me since all eight of them were 1's. Thanks for the help. Next thing is to see if the output actually works as a clock source for something that I am trying to drive. My oscilloscope shows a pretty funky waveform coming out of the pins but it will probably be OK. I stuck a high speed buffer onto my prototype board just in case.
  
  -Jack
• Timothy D. Swieter Posts: 1,613

  2010-02-27 01:19 edited 2010-02-27 01:19

  What kind of funky output? Can you show a screen shot of the signal? The clock/counter output should work well as a clk for a high speed output as others have done it and I myself am working through a design as well.
  
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  Timothy D. Swieter, E.I.
  www.brilldea.com - Prop Blade, LED Painter, RGB LEDs, 3.0" LCD Composite video display, eProto for SunSPOT
  www.tdswieter.com
• Jack Buffington Posts: 115

  2010-03-13 00:53 edited 2010-03-13 00:53

  I saw a lot of ringing and other quirks in the signal coming out but eventually tamed it by just adding a series resistor.
  
  The ringing was shooting a good volt above and below my power rails.
• Phil Pilgrim (PhiPi) Posts: 23,514

  2010-03-13 02:35 edited 2010-03-13 02:35

  The ringing you observed is likely due more to your measurement technique than to the Propeller's actual output behavior. The Propeller outputs have extremely fast rise times. Unless you use scope probes without their clips and with very short ground leads (i.e. a short wire attached to the ground ring and soldered directly to the board), you will see the apparent ringing that you report.
  
  -Phil
• Jack Buffington Posts: 115

  2010-03-13 04:50 edited 2010-03-13 04:50

  I'm pretty sure that my scope is fine. The signal coming out of the calibration post looks fine and has no over/under shoot. It is a nice crisp square wave. At first I was testing on the propeller demo board so I can see that things wouldn't be ideal but now I am working on a printed circuit board where I'm using the lqfp part and the trace to the other part is about 1 1/4 inches long with no sharp angles or vias.
  Here is how it looked before the series resistor:
  
  
  And here it is afterwards;
  
  
  It still isn't perfect but looks better to me. Probably both are really fine for my application but I am driving the clock to an A/D so I was worried about the over and under shoot adding noise to my data.
  
  I should say that I am overclocking this propeller to 100MHz rather than 80MHz. I'm not sure if that really matters since I am only having the counter run at 25MHz so the output driver isn't being pushed faster than it is spec'd for. Also, looking at my own picture, I see that at least as I was measuring it there, it was only ringing about .75V above and about .6V below the rails but still....
  
  -Jack
• hover1 Posts: 1,929

  2010-03-13 12:41 edited 2010-03-13 12:41

  There was a recent thread on the ringing problem. A series resistor was the solution.
  
  ·http://forums.parallax.com/showthread.php?p=885691
  
  Jim