LPC MicrocontrollersのトピックRe: StopWatch_DelayUs function is not correct in LPC1830

StopWatch_DelayUs function is not correct in LPC1830

kensu — Tue, 25 Jul 2017 07:31:28 GMT

Hi, I am using StopWatch_DelayUs API to make delay in LPC1830 MCU application.

I use 5us delay, but the measure is ~120us ( to use GPIO high low), it seems this API is not correct.

But if I use the lpc_chip_18xx StopWatch_DelayMs to make "5ms" delay. After measure confirm, it is correct.

Why does the StopWatch_DelayUs not work?

Does LPC1830 not support Us delay?

BTW: my application is debug mode, should I use "release" mode? Does it improve the application performance?

Thanks

Ken

Re: StopWatch_DelayUs function is not correct in LPC1830

soledad — Thu, 03 Aug 2017 22:57:34 GMT

Hi,

Unfortunately I cannot to reproduce your issue. I tested using the blinky example from LPCOpen.

You need to consider the time that the instruction to turn/off the PIN requires, this time is not important when you use a (ms) delay, however when you use a (us) delay then this time it is significant.

I used the OM13076 lpcxpresso 18xx board.

Attached you can find my code.

Have a great day,
Sol

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Re: StopWatch_DelayUs function is not correct in LPC1830

kensu — Fri, 04 Aug 2017 00:41:29 GMT

Hi Sol

Thanks for your checking.

I find the cause about "us delay" problem, if I use LPC1857, it works correctly, and if I use LPC1830 it works NG.

Because the LPC1857 has internal flash and LPC1830 use external flash, I think the instruction fetch is a factor.

After I put the code into SRAM or Config project to Release mode with optimize option, it works correctly.

Thanks

Ken