Hello. You should know that 14 bit core has only 8 bit stack levels.
It's mean that the 14 bit core is C unfriendly. The 16 bit core or
18f4550 has 31 bit stack levels.
There are still a lack of documentation about the Sdcc port for pic. But
i will try to show you something i have learned.
The header file of pic16f690 can tell you a lot of things that you must
know to
programming the Pic uc.
In the directory */usr/share/sdcc/include/pic/* you can find all the
header file to the port14
In the pic16fxxx header file there are the special function registers
and its bits.
RA0=0;
RA1=1;
PORTB=2;
GIE=0;
The sdcc can recognize decimal , binary and hexadecimal numbers. Ex:
PORTA=0xFF; // PORTA=255
PORTA=0b11111111; // PORTA=255
PORTA=255; // (default decimal)
Remember that C programming to mcu is not same as the C to intel x86.
There aren't the standard I/O library, printf , scanf ...
Its common to do the following:
There are the following data types that you must know to perform
embedded system programmig:
char / uint_8t: 8 bits Range 0 to 255
unsigned char / int_8t : 8 bits Range -127 to 128
unsigned int / uint_16t : 16 bits Range 0 to 65535
int / int_16t : 16 bits Range ????
float / float : 32 bits
==============
The SDCC compiler don't have a built-in delay routine like the CCS
compiler eg.:
#pragma use clock 40000.
void main{
delay(500);
}
you should do it by yourself.
==============
You must also know the bit-masks techniques :
Bitwise operatiors:
& and operator
| or operator
~ not operator (inverter)
>> left shift
<< right shift
^ xor operator
CODE= PORTA & 0b10000011 ; // Read the RA7, RA1 and RA0 bits
Ex PORTA = 11001101
& 10000011 ( bit mask)
------------------
10000001 (masked result)
Eg.: read the PORTA hight nibbles :
NIBBLES= PORTA >> 4;
Eg.:
Blink all leds in PORTA.
CODE= 0b1111111;
while(1){
PORTA=PORTA^CODE;
delay_500();
}
....
....
==============================
You should avoid complex math and store constant data in program memory
by storing the data on program memory (flash memory).
Note that *__code* directive forces the data to be stored in the flash
memory( program memory).
Eg.:
#include <xxxx.h>
#define u8 char
.....
void main(){
TRISA=0x00;
PORTA=disp7seg(8); // Display digit 8 on the seven segment display
}
#if 1
static u8 disp7seg(u8 digit){
__code u8 LookUpTable[10]={ // It is stored in the program
memory __code
0x3F, // Disp 0
0x06, // Disp 1
0x5B, // Disp 2
0X4F, // Disp 3
0x66, // Disp 4
0x6D, // Disp 5
0x7D, // Disp 6
0x07, // Disp 7
0x7F, // Disp 8
0x6F, // Disp 9
0x00 // Digito nulo se requerido
};//End of LookUpTable
return LookUpTable[digit];
}
#endif
Excuse my English, it's not my native language,I am from Brazil.
Best regards.
On 08/22/2010 11:44 PM, Bob Cochran wrote:
Greetings,
I am a new SDCC user. I have succeeded in compiling, flashing and
running a simple LED-blinking program for the PIC16F690 on a breadboard.
I am new to embedded programming and very new to writing embedded C
programs. I learned about SDCC in my search for an open source PIC
device compiler.
Where can I find examples of C programs which are compiled on SDCC for
the PIC14 port? I would like to study these so I can learn from more
advanced programmers.
Thanks
Bob Cochran
Greenbelt, Maryland
USA
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