Kinetis Microcontrollersのトピック(void)

(void)

nikivendola — Wed, 16 Mar 2016 07:27:36 GMT

Hello,

in a program that runs the ASL of a MK10 the following statement appears that I can not understand:

if (uart-> S1 & UART_S1_RDRF_MASK) {(void) uart-> D;}

I do not know what means the (void). I can explain?
Thank you

Re: (void)

Alice_Yang — Wed, 16 Mar 2016 07:50:03 GMT

Hello niki,

I think this is just read the D register , the aim is clear the RDRF Flag.

You can see this in the RM

you can confirm it through the your project .

Hope it helps

Have a great day,
Alice Yang

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Re: (void)

nikivendola — Wed, 16 Mar 2016 09:47:48 GMT

Yes, this is ok, but do not understand the void put in the brackets. And 'an education that I never found. What does?

Re: (void)

mjbcswitzerland — Wed, 16 Mar 2016 13:59:14 GMT

uart->D;

causes a read of the register D to take place. However, the compiler will often generate a warning because the read value is not being used.

(void) uart->D;

does the same but stops the compiler generating the warning.

Therefore the (void) cast is used to quieten the compiler.

Regards

Mark

Re: (void)

nikivendola — Wed, 16 Mar 2016 14:41:28 GMT

The (void) is used only in this case, or may have other uses?

Thank you and greetings

Re: (void)

mjbcswitzerland — Wed, 16 Mar 2016 14:58:36 GMT

The use of (void) is explained (in German) at

https://de.wikipedia.org/wiki/Void_%28Schl%C3%BCsselwort%29

with links to further details in the C-programming guides/books.

These are the best sources for such a topic.

Regards

Mark

Re: (void)

nikivendola — Wed, 16 Mar 2016 16:30:27 GMT

ok, you can also recommend a guide for learning the interrupt handling in freescale?

Re: (void)

mjbcswitzerland — Wed, 16 Mar 2016 20:48:09 GMT

The ARM web site gives details of the Cortex interrupt handling and this is the best source for core-related details: http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0439b/CHDIHEAF.html

For Kinetis peripheral details (including interrupt and DMA operation) the Kinetis user manual should be used.

For most practical learning and efficient developments the uTasker project allows all the details to be simulated and studied (from NVIC through peripherals, interrupts and DMA to full project simulation without the normal guessing games): eg. http://www.utasker.com/kinetis/TWR-K60N512.html

Regards

Mark