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How to use invert bit in define command by macro

 
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huynhhai



Joined: 04 Apr 2015
Posts: 39

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How to use invert bit in define command by macro
PostPosted: Fri Feb 11, 2022 9:05 pm     Reply with quote

Hi Everyone,

I had one a hardware, now i want to write code to use it, (my PIC16F886)
in the define line: #define led PIN_C5


the code in my program:

output_high(led); --> PIN_C5 will come 1

my question:
output_high(led); --> PIN_C5 will come 0, it mean PIN_C5 will be invert bit from 1 to 0

OR output_low(led); --> PIN_C5 =1??

how i change #define led PIN_C5 ??

Please help me about them.

Regarsd
huynhhai
temtronic



Joined: 01 Jul 2010
Posts: 9081
Location: Greensville,Ontario

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PostPosted: Fri Feb 11, 2022 9:11 pm     Reply with quote

output_high means the pin will set high (+3 or +5), whatever VDD is
output_low means the pin will set low (zero)

As to whether a high turns on the LED, depends on how the LED and it's resistor are wired.
If the Anode of the LED is on the port_pin and it's resistor tied to ground, then a high will turn on the LED.
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Fri Feb 11, 2022 9:47 pm     Reply with quote

I'm not sure what you want, but look at output_toggle() to invert a pin.
huynhhai



Joined: 04 Apr 2015
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How to use invert bit in define command by macro
PostPosted: Fri Feb 11, 2022 10:30 pm     Reply with quote

I can use macro to write code on command #define such as output_toggle(),

Regards
Ttelmah



Joined: 11 Mar 2010
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PostPosted: Sat Feb 12, 2022 3:04 am     Reply with quote

Key here is the concept of 'reserved words'. No, you cannot change the
meaning of a reserved word with a macro. Output_high and output_low
are reserved words. If you did change these, it would make every library
not work, etc. etc.
Use your own keyword. So:
Code:

#define LED_ON(x) output_low(x)

Then to turn the LED 'ON' you use LED_ON(PIN). If you want 'ON' to be
high or low, you can just change the define.
huynhhai



Joined: 04 Apr 2015
Posts: 39

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How to use invert bit in define command by macro
PostPosted: Sun Feb 13, 2022 11:16 pm     Reply with quote

Thank you very much for you help, i solved it by changed code in programs (changed library).

Regards,
huynhhai
PrinceNai



Joined: 31 Oct 2016
Posts: 452
Location: Montenegro

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PostPosted: Mon Feb 14, 2022 12:08 pm     Reply with quote

I'm sure it works. For now. And only for you. If you update the compiler, those libraries will be overwritten. If you have a copy in your project folder, you'll have two different libraries with the same name doing opposite things. The way all the other guys told you to do it is for a reason. Many reasons, actually. Who on earth would think that output_low actually sets the bit? That is why the function name is output_low. It outputs low. You wouldn't code a start() function to stop something :-)
temtronic



Joined: 01 Jul 2010
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Location: Greensville,Ontario

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PostPosted: Mon Feb 14, 2022 1:46 pm     Reply with quote

re:
Quote:
You wouldn't code a start() function to stop something :-)


gee, that's how most of my projects work ! Very Happy
'start' begins the 'stopping' process.....sigh.
even more fun when there's 3 outputs(start,stop, and 'inbetween') !

Man I hated 'inverse' logic designs with 7400 series chips, then found 7486(?) where I could use one pin to control output high if input high; or low if input high;stuff.....or is that 'active low', arrgh it's easy to confuse this dinosaur !

he could create a 'my_output_high()' function to do whatever.....
or a 'conditional' within the program based on hardware ?
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