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stevech
Joined: 23 Feb 2006
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Posted: 11 August 2006, 3:14 AM Post subject: demo of sleep() for 1 sec excluding application loop time |
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This program prints the current time as
hh:mm:ss.s fractions of second
based on the the VM's RTC
it then sleeps for the remainder of one second.
That is, it sleeps for 1 second minus the time to compute and output to a queue the time string.
the sleep() function is used with some math to compute how long to sleep.
Simple but possibly useful example.
there's also an LED blinker: red/green/both, brief flashes once/sec
| Description: |
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Download |
| Filename: |
sleepLessOverhead.bas |
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1.46 KB |
| Downloaded: |
1042 Time(s) |
| Description: |
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| Filename: |
sleepLessOverhead.pjt |
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23 Bytes |
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1069 Time(s) |
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dkinzer
Site Admin
Joined: 03 Sep 2005
Location: Portland, OR
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Posted: 11 August 2006, 4:07 AM Post subject: |
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That is a nice example. A couple of items to note:
1) The RTC tick frequency is available as an UnsignedInteger value Register.RTCTickFrequency. The value is returned by the VM at run time so that if future ZX models have a different RTC tick frequency your code will automatically adapt.
2) Another way to accomplish the same goal of equal interval execution is to use WaitForInterval(). A modified version of your code (omitting the unchanged parts) is shown below.
| Code: | Private intervalTaskStack(1 to 60) as Byte
sub main()
Calltask blinkLED1, blinkled1stack
CallTask IntervalTask, IntervalTaskStack
Do
Loop
end sub
Sub IntervalTask()
Call SetInterval(1.0) ' set a 1 second interval
Do
Dim h as Byte, m as Byte
Dim sec as Single
Dim s as string
WaitForInterval(0)
Call GetTime(h, m, sec)
' make string like 00:00:00.0 time
s=byteToAscii2(h) & ":" & byteToAscii2(m) & ":" & _
byteToAscii2(cbyte(sec)) & "." & byteToAscii2(cbyte(100.0 * fraction(sec)))
console.writeline(s)
Loop
End Sub
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stevech
Joined: 23 Feb 2006
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Posted: 11 August 2006, 4:44 AM Post subject: |
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Thanks for the kind words.
I (finally, as a noobie) interpreted SetInterval() and WaitForInterval() to say that the interval timer is global to all tasks, i.e., there is not a per-task interval counter. So my thinking in my code was to wait for the remainder of the time slot (one second in my example) to expire without a shared-use interval timer amongst all tasks. But I can see other situations where SetInterval as a global timer would be useful.
A nit pick: I might suggest taking a crack at rewording and clarifying the second paragraph if WaitForInterval() - it's kinda obtuse to me. I read these several times thinking the interval timer was per-task, since that's what I'm kind of used to in other OSes.
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