VojtVojtěěchch KrmKrmííččekek
vojtec@vojtec@icsics..munimuni..czcz
PIC12Fxxx
Programming PIC in C
PIC12FxxxPIC12Fxxx
ProgrammingProgramming PIC in CPIC in C
CC IntroductionIntroduction
WWe can use high level language C to avoide can use high level language C to avoid
writing a code in assembly codewriting a code in assembly code
C compiler converts C code to theC compiler converts C code to the
assemassembblerler codecode
WeWe cancan useuse debuggerdebugger toolstools in MPLABin MPLAB forfor
debuggingdebugging ­­ steppingstepping,, watchwatch,, memorymemory
listinglisting,, disassemlbydisassemlby listinglisting,, ......
Logic Operations in CLogic Operations in CLogic Operations in C
Operations with bits:Operations with bits:
&& -- ANDAND
|| -- OROR
^^ -- XORXOR
<<<< -- shift to leftshift to left
>>>> -- shift to rightshift to right
~~ -- negationnegation
Operations with bytes:Operations with bytes:
&&&& -- ANDAND
|||| -- OROR
ExpressingExpressing NumbersNumbers
NumberNumber DefinitionsDefinitions
unsigned char x;unsigned char x; //// 8 bits on PIC8 bits on PIC
x=255;x=255; //// givegive decimaldecimal numbernumber
x=0xFF;x=0xFF; //// give hex number, x=255give hex number, x=255
x=0b11111111;x=0b11111111; //// give binary number, x=255give binary number, x=255
WhatsWhats wrong with the following code?wrong with the following code?
unsigned char i;unsigned char i;
ffor (i=7;i>=0;ior (i=7;i>=0;i----) { }; //will loop forever) { }; //will loop forever
AvailableAvailable DatatypesDatatypes on a PICon a PIC
unsigned char a; //8 bits, 0 to 255unsigned char a; //8 bits, 0 to 255
signed char b; //8 bits,signed char b; //8 bits, --128 to 127128 to 127
unsignedunsigned intint c; //16 bits, 0 to 65535c; //16 bits, 0 to 65535
signedsigned intint d; //16 bits,d; //16 bits, --32768 to 3276732768 to 32767
long e; //32 bits,long e; //32 bits, --2147483648 to2147483648 to
21474836472147483647
float f; //24 or 32 bits, depending onfloat f; //24 or 32 bits, depending on
options underoptions under ``edit projectedit project''
bit g;bit g; // 1bit, 0// 1bit, 0 oror 11
SwitchingSwitching Bit inBit in VariableVariable
unsigned char x = 0b10010101 // var. definition
Setting bit number bitno:
x = x | (1 << bitno);
Clearing bit number bitno:
x = x & ~(1 << bitno);
We can use macros:
#define bit_set(var,bitno) ((var) |= 1 << (bitno))
#define bit_clr(var,bitno) ((var) &= ~(1 << (bitno)))
Handling InterrputsHandlingHandling InterrputsInterrputs
compilercompiler automaticallyautomatically managesmanages savingsaving
ofof contextcontext (STATUS(STATUS andand WW registersregisters))
void interruptvoid interrupt tc_int(voidtc_int(void))
{{
if (T0IE && T0IF) {if (T0IE && T0IF) {
T0IF=0;T0IF=0;
++++tick_counttick_count;;
}}
}}