1 #include <stdio.h> 2 3 #define MASK_SPIE 0x80 4 #define MASK_SPE 0x40 5 #define MASK_CPOL 0x08 6 #define MASK_SPR1 0x04 7 #define MASK_SPR0 0x02 8 9 #define SHIFT_SPIE 7 10 #define SHIFT_SPE 6 11 #define SHIFT_CPOL 3 12 #define SHIFT_SPR1 2 13 #define SHIFT_SPR0 1 14 15 typedef unsigned char uchar; 16 typedef enum { LO, HI } bit_t; 17 18 bit_t getSPIE(uchar); 19 bit_t getCPOL(uchar); 20 uchar getPrescalingFactor(uchar SPCR); 21 22 void getCOMControl(uchar control, uchar *prescalingFactor, uchar *divisionFactor); 23 void setCPOL(uchar *, bit_t); 24 25 int main (void) 26 { 27 uchar SPCR = 0xCE; /* 1100 1110 */ 28 29 printf("Interrupciones: %s\n", getSPIE(SPCR) ? "habilitadas" : " deshabilitadas"); 30 printf("Reloj activo: %s\n", getCPOL(SPCR) ? "nivel bajo" : "nivel alto"); 31 printf("Factor de division: %d\n", getPrescalingFactor(SPCR)); 32 33 printf("0x%X\n", SPCR); 34 35 /* Sets CPOL bit to LOW */ 36 setCPOL(&SPCR, LO); 37 38 printf("0x%X\n", SPCR); 39 40 return 0; 41 } 42 43 bit_t getSPIE(uchar SPCR) 44 { 45 return (SPCR & MASK_SPIE) >> SHIFT_SPIE; 46 } 47 48 bit_t getCPOL(uchar SPCR) 49 { 50 return (SPCR & MASK_CPOL) >> SHIFT_CPOL; 51 } 52 53 uchar getPrescalingFactor(uchar SPCR) 54 { 55 static uchar divFactor[4] = { 2, 4, 16, 32 }; 56 return divFactor[(SPCR & (MASK_SPR0 + MASK_SPR1)) >> SHIFT_SPR0]; 57 } 58 59 void getCOMControl(uchar control, uchar *prescalingFactor, uchar *divisionFactor) 60 { 61 if(!prescalingFactor || !divisionFactor) return; 62 63 /* static because otherwise it would have to load the array into memmory everytime the function is called */ 64 static uchar divFactor[4] = { 2, 4, 16, 32 }; 65 66 *prescalingFactor = ((control & (MASK_SPR0 + MASK_SPR1)) >> SHIFT_SPR0); 67 *divisionFactor = divFactor[*prescalingFactor]; 68 } 69 70 void setCPOL(uchar *control, bit_t CPOL) 71 { 72 if(!control) return; 73 74 *control = ((*control & ~MASK_CPOL) + (CPOL << SHIFT_CPOL)); 75 }
