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[vox-tech] Must a 300 microsecond delay keep the CPU busy?
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[vox-tech] Must a 300 microsecond delay keep the CPU busy?

Dear Group,

I'm writing a C program on my Debian system to read from an interface board through the parallel port. I need to wait at least 300 microseconds before reading from the next channel, to give the A/D converter on the board time to stabilize, but I don't want to wait much longer (e.g., 10 milliseconds) because it will make the program too slow. The delay functions (usleep, nanosleep...) only provide delays down to 10-30 milliseconds, despite their name, because they apparently yield the CPU to other tasks with every call. The best solution I've found it to read (or write) to a port (e.g., 0x80), which takes one microsecond. By doing this 300 times, I get something close to the wanted delay, plus a little because of time sharing, but it is good enough. The only thing I don't like is that my process takes about 97% of the CPU, even though it spends almost all its time waiting. The CPU is a fanless 386, and it runs pretty hot at 97% usage. Is there an elegant solution to this, or should I look for a CPU fan? I would like to leave this a time-sharing system.


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