spin equivalent to arduino pulsin

Comments

• JonnyMac Posts: 9,375

  2016-02-26 17:13 edited 2016-02-27 05:35

  There is no Spin command for pulseIn, but it's easy to duplicate in a method. Here's a simple version that measures a 0-1-0 pulse in microseconds.
  

  pub ez_pulse_in(pin) | ticks
  
    waitpne(|<pin, |<pin, 0)                                      ' wait for pin to be low
    waitpeq(|<pin, |<pin, 0)                                      ' wait for pin to go high
    ticks := -cnt                                                 ' start timing
    waitpne(|<pin, |<pin, 0)                                      ' wait for pin to go low
    ticks += cnt                                                  ' stop timing
  
    return ticks / (clkfreq / 1_000_000)                          ' return pulse width in microseconds
  

  
  Note that this method doesn't have any tuning for command overhead. The great thing about the Propeller is that you could use another cog to create precision pulses on a pin, then use this method is a second cog to measure them to determine a tuning constant.
• BenDeLathouwer Posts: 11

  2016-02-26 18:34

  thanks for the info. now i have an other question. Is it posible to blow up the propellor mini if you conect a function generator and an oscilloscoop to an input pin?(my input signal was 3.3V puls signal)
• JonnyMac Posts: 9,375

  2016-02-26 20:13

  Anything is possible. If any of your cogs makes a pin an output, it's an output. Accidents happen. Resistors are cheap insurance. Use a 4.7K or 10K until you know your code is working as expected; if your signal is 3.3 or lower they resistor won't matter; it's its higher than 3.3 it will limit the current through the pin's protective diodes.
• Electrodude Posts: 1,673

  2016-02-26 20:36 edited 2016-02-26 20:37

  That pulse width isn't microseconds, it's 80ths of a second (for clkfreq = 80MHz). Replace the last line with:

    return ticks / constant(clkfreq / 1_000_000)
  

  to make it microseconds.
• JonnyMac Posts: 9,375

  2016-02-27 05:33 edited 2016-02-27 05:34

  Lowercase clkfreq is not a constant; it's a run-time system variable (and can be changed using the correct technique). That said, you're correct that I erred in my code. It's fixed now.
  
  In my own programs I use this header (mod of something someone posted in these forums) to create compile-time constants for clock frequency, and ticks in milliseconds and microseconds.
  

  con { timing }
  
    _clkmode = xtal1 + pll16x                                     
    _xinfreq = 5_000_000                                          ' use 5MHz crystal
  
    CLK_FREQ = (_clkmode >> 6) * _xinfreq                         ' system freq as a constant
    MS_001   = CLK_FREQ / 1_000                                   ' ticks in 1ms
    US_001   = CLK_FREQ / 1_000_000                               ' ticks in 1us