Make a Fake LED

Humanoido · 2010-08-31 04:54

[FONT=&quot]There are 2 methods below for blinking two real LEDs at different rates. I want to change real LEDs to fake LEDs where nothing exists, but the identical timing is maintained. It appears, to accomplish this, the outa statement needs a substitute statement with exactly the same timing. If it's true that statements take 4 cycles, then any other Spin statement could serve as a replacement. Is this true, and which statement could be substituted? Thanks in advance. Humanoido

'

[/FONT][FONT=&quot]PRI task0 ' Private Method - Task 0
case state0 ' Flash LED1 every second
OFF:
if (ms // 500) == 0
outa |= %01 ' Pin 0 on Main Header
state0 := ON
ON:
if (ms // 500) == 0
outa ^= %01 ' Pin 0 on Main Header
state0 := OFF
'

PRI task1 ' Private Method - Task 1
case state1 ' Flash LED2 twice every second
OFF:
if (ms // 250) == 0
outa |= %10 ' Pin 1 on Main Header
state1 := ON
ON:
if (ms // 250) == 0
outa ^= %10 ' Pin 1 on Main Header
state1 := OFF
[/FONT][FONT=&quot]'

[/FONT]

Roger Lee · 2010-08-31 05:18

[FONT=&quot]outb |= %01
.
.
.
[/FONT]

PJAllen · 2010-08-31 05:38

This would be a great application for the fake LED touch sensors!

kuroneko · 2010-08-31 05:43

Humanoido wrote: »

If it's true that statements take 4 cycles, then any other Spin statement could serve as a replacement.

(Most) assembler instructions take 4 cycles. Anyway, leave outa statements as they are just don't touch dira for the relevant bits.

RinksCustoms · 2010-08-31 08:33

From your description, it sounds like you want to utilise a waitcnt command instead.

waitcnt(value) = Wait until the system counter = value (page 219 in the manual)

waitcnt(clkfreq + cnt)
simply waits for exactly 1S, regardless of the system clock value

waitcnt(clkfreq / 2 + cnt)
takes current clock frequency, divides it by half then waits until system counter matches the calculated clock ticks of 1/2 clkfreq plus current system counter reg value (0.5 sconds). Also variables can be passed to the equation as well, ie;
waitcnt(clkfreq / x * a + cnt)

waitcnt(clkfreq / 1000 * 39 + cnt)
divide current system clkfreq reg value by 1mS, then multiply the 1mS by 39 to get a binary value for 39mS based on the current clkfreq reg value, then adds that to the system counter value and then proceeds to wait for the 39mS you specified.
Traps:
*always specify it as (offset + cnt) not (cnt + offset), the latter does the math (optional) and then activates the wait hardware in the cog.
*in spin value absolute minimum = 381, the overhead number of clocks it takes the interpreter to evaluate the expression, equation or not.
Tip:
*pre calculating those values used often and refrencing them as constants or variables for use in your entire program code or just in a pri block

**Also note that SPIN commands/programs are many times slower in execution than PASM equivalents and most SPIN commands take many more than 4 clocks to complete, the waitcnt command for example takes at least 381 clocks. Using the counter A/B modules within the cog, you can produce basic square waves/frequencies up to 128MHz using PLL and/or NCO modes but the spin program runs 1,000's of times slower than that. You can even use the special waitvid command to pass the video hardware -after setting the appropriate bits in the vconfig reg- bit patterns to shift out over 4 to 8 i/o such as how the TV and VGA drivers accomplish output.

If your looking to toggle/pulse an output with optional output disable you can simply do:

pri task_0( OE, mS, blink_num):ok | val, led
{
This pri block does a few things,
*blink_num =  controls the number of blinks on the output
*mS        =  desired square wave freq with 50% duty cycle
*OE        =  Output Enable - enables one of two output pins depending on value passed by mS
If blink_num or OE is 0 then task_0 will simply wait for mS & return
}
  val := clkfreq / 2000 * mS    'calculate correct pause time in milliseconds, store result in val
  if(val <> 250 OR val <> 125) 'if mS doesn't equal 500mS OR 250mS then the method quits and does nothing
    ok := false
    return
  if val == 250                 'if mS == 500mS then..
    led := 1                    
  if val == 125                 'if mS == 250mS then..
    led := 2                    
  dira[led] := OE               'enable output = 1, disable = 0
 
  if(blink_num == 0 OR OE == 0) 'if blink_num = 0 OR OE = 0, then wait for mS and return
    repeat 2
      waitcnt(val + cnt)        'pause cog opperation until mS has passed
    ok := true
    return                      
 
  if blink_num                  'if blink_num = true then repeat number of blinks
    repeat blink_num            
      !outa[led]                'toggle logic state of led
      waitcnt(val + cnt)        'pause cog opperation until mS has passed
      !outa[led]                'toggle back to original state
      waitcnt(val + cnt)        'pause cog opperation until mS has passed
    ok := true
return

Make a Fake LED

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