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cog problem... but code seems right — Parallax Forums

cog problem... but code seems right

sovsov Posts: 17
edited 2010-07-23 15:19 in Propeller 1
hello, I have been doing a contest with my school for some time. But since it has been a couple months since I have really worked on propeller I am having trouble with the cognew command or any other cog command. With the code I put within this post seems right to me, but every time I try it out the cog command would fail. Is it because I have a 6.25 mhz crystal instead of a 5mhz crystal (6.25 mhz makes propeller run at 100mhz) or is it a silly mistake that I can not figure out, thank you in advance!!
con
        _clkmode = xtal1 + pll16x
        _xinfreq = 6_250_000
obj

        debug : "FullDuplexSerial"
var
        long microseconds, stack[noparse][[/noparse]10],success

pub start
    debug.start(31,30,0,57600)
    dira~~
    repeat
      success := (cognew(ticks(0),@stack[noparse][[/noparse]10]))
      if success > 0
        outa~
      if success == -1
        outa~~
      debug.dec(success)
      
      
     
PUB Ticks(Pin) | cnt1, cnt2
''Return Ping)))'s one-way ultrasonic travel time in microseconds
 repeat                                                                                
  outa[noparse][[/noparse]Pin]~                                                                    ' Clear I/O Pin
  dira[noparse][[/noparse]Pin]~~                                                                   ' Make Pin Output
  outa[noparse][[/noparse]Pin]~~                                                                   ' Set I/O Pin
  outa[noparse][[/noparse]Pin]~                                                                    ' Clear I/O Pin (> 2 µs pulse)
  dira[noparse][[/noparse]Pin]~                                                                    ' Make I/O Pin Input
  waitpne(0, |< Pin, 0)                                                         ' Wait For Pin To Go HIGH
  cnt1 := cnt                                                                   ' Store Current Counter Value
  waitpeq(0, |< Pin, 0)                                                         ' Wait For Pin To Go LOW 
  cnt2 := cnt                                                                   ' Store New Counter Value
  Microseconds := (||(cnt1 - cnt2) / (clkfreq / 1_000_000)) >> 1

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Comments

  • sovsov Posts: 17
    edited 2010-07-22 22:39
    I am sorry please look at the file instead of the code in the post, thank you!

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    iPhone expert
  • Bobb FwedBobb Fwed Posts: 1,119
    edited 2010-07-22 22:42
    try
    success := (cognew(ticks(0),@stack))

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  • KyeKye Posts: 2,200
    edited 2010-07-22 23:08
    Do you mean:

    @stack[noparse][[/noparse]10]? - That seems wrong.

    Also, your code seems to just launch a bunch of cogs using the same I/O pin until it runs out of them.

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  • MagIO2MagIO2 Posts: 2,243
    edited 2010-07-23 15:19
    COGNEW won't wait until the·function is finished! It won't even wait until it's started, so you will end up running 7 COGs.
    COGNEW is only the instruction to trigger the start of a new COG. It takes 512 HUB-cycles until the COG is completely loaded (with another SPIN-interpreter in your case). BUT ... the COGNEW immediately returns to your main-loop. So, the variable success will be 0 when you read it first.

    The second parameter of the COGNEW is the start of the stackspace that the additional SPIN-interpreter shall use. @stack[noparse][[/noparse]10] is pointing to the first long AFTER the array stack. But in SPIN the stack grows bottom-up whereas in other systems the stack grows top-down - maybe that's why you thought it's right this way.

    Whether SPIN is fast enough to measure the travel-time of a ultrasonic signal I don't know. But is this code right at all? You are not interested in the high-time of the signal. You are interested in the time it took between sending and receiving. But I have to admit that I don't know the PING and might be wrong here.
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