I2C problems ???

small_chick · Joined: 17 Jul 2012 Posts: 53

I have some questions about I2C, I hope you can help me! However, the content seems fairly long to display here, so I put all in pdf, you can download it here ! sorry for this inconvenience !!!
http://www.mediafire.com/view/?8jjm57b68ao3tkm

Rohit de Sa · Joined: 09 Nov 2007 Posts: 282 Location: India

You really could have made this much easier for others. There was absolutely no need to use a PDF. That's probably why you've not yet got answers. Your questions should simply have been:

small_chick · Joined: 17 Jul 2012 Posts: 53

I suppose that "hardware functions" means what PIC really does without being programmed ! Is it what you mean, Rohit de Sa ?

temtronic · Posted: Fri Jul 20, 2012 8:20 pm

'hardware functions' refers to a 'module' that the PIC may have , built internally. UART,eeprom,timers,PWM,ADC,DAC,etc.
In the beginning, microcomputers consisted of the ALU and a few I/O pins.Everything(UARTS,adc,ram,eeprom,etc) were external 'devices' or 'modules' that were added to the computer to do certain tasks.
Over the past 40 years, many of these external 'modules' have been built into the main computer 'core'.
One example is the UART.
It takes a fair amount of code to allow a PIC or other computer to act as a UART (serial communications) ,having a builtin 'hardware' UART greatly simplifies the coding(programming) process however hardware modules have limitations.One is that generally speaking hardware 'functions' are physically 'tied' to 'specific' I/O pins.
A 'software' based UART is also referred to as 'bit-banging',where the programmer cuts code on a bit by bit level to do the UART functions.Since you , the programmer is in total control, you can assign the 'software UART' to any I/O pin.

One of the key benefits of using 'software' based functions or modules is that you can have, say, several UARTs, I2C busses,or One Wire busses depending on the project's requirements.

Obviously there are 'pros and cons' to using either of these techniques,entire books can (and have) been written about this subject and goes beyond the scope of this forum.As a general 'rule', projects always will need more pins,functions and memory so it's better to buy say 40 pin devices even though a 28 pin PIC should do.

hth
jay

small_chick · Joined: 17 Jul 2012 Posts: 53

Thanks for your explanation, temtronic !!!

Ttelmah · Joined: 11 Mar 2010 Posts: 19539

And from your other thread, # commands, are _preprocessor_ directives, not lines of C code.
Read any C book, and you will see such commands being used, and they _do not_ have the trailing ';' needed by a line of C. Hence the compiler complains when you include this....

Best Wishes

small_chick · Joined: 17 Jul 2012 Posts: 53

I have a problem as follow:
I use i2c functions but the header file of PIC doesn't define anything related to i2c. Therefore, when i use this direction "#use i2c(master);", there's an error:
Error 104 "main.c" Line 4(5,18): Extra characters on preprocessor command line ";"
//***********************
how can i use i2c functions recommended by CCS ? please help me! thanks!
I use PIC16F887.
And one more question is that:
is it always necessary to have a header file with the same name as the .c file, for example lcd.h & lcd.c ,... ?
If I have already defined all functions and variables in .c file, do i need to create a header file corresponding to the .c file ?
And how can I create a header file and a .c file ? is it able to do this with notepad ?
I'm looking forward to receiving your replies ! thanks !

jeremiah · Joined: 20 Jul 2010 Posts: 1354

If you read Ttelmah's post right above yours and if you read the error itself, it will tell you what is wrong with that call (though you should be using some other options as well, but that is not a compiler error).

For your second question, file names can be whatever you want. Most find it useful to name the .c and the .h the same for organizational purposes, but you don't have to name them the same.

gpsmikey · Joined: 16 Nov 2010 Posts: 588 Location: Kirkland, WA

If you read Ttelmah's post just above yours, he explains your error message about the pre-processor directive.

The .h files are usually used to define constants and other things that are used in the .c program - they are usually the same name as the "c" file simply to make it clear what they are for, HOWEVER, every C file does not need a .h file and often you will see includes for .h files that do not have an associated .c file (io.h, system.h, lcd.h pic16f14k22 etc). Get yourself a decent C book and look through it many things will be explained.

mikey
_________________
mikey
-- you can't have too many gadgets or too much disk space !
old engineering saying: 1+1 = 3 for sufficiently large values of 1 or small values of 3