Thank you very, very much for your help to me!
I will study this more carefully over the next few days. You made some
comments that are extremely helpful to me. Thank you for taking the time
to help a complete beginner.
Bob Cochran
On 08/26/2010 12:45 AM, caio wrote:
> 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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