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;;
}}
}}