bit shift - 74hc595 Cascading -
i have problem spi protocol. have 2 74hc595 cascade register , connected 7 segment.
i have following pattern displaying numbers:
static const uint8_t pattern[] = { 0b01000000, // 0 0b11101001, // 1 0b00100010, // 2 0b10100000, // 3 0b10001001, // 4 0b10000100, // 5 0b00000100, // 6 0b11100001, // 7 0b00000000, // 8 0b10000000, // 9 0b11101111}; // blank but can't execute program; there shift in bits when want display number 1 or 4 or 7.
i noticed these 3 figure ends bit 1 (the problem is):
0b1110100**1**, // 1 0b1000100**1**, // 4 0b1110000**1**, // 7 with other numbers (0,2,3,5,6,8,9) program works well.
here program:
#define f_cpu 1000000ul #include <avr/io.h> #include <util/delay.h> //#define chek_bit(var,pos) ((var) & (1 << (pos))) #define hc595_port portc #define hc595_ddr ddrc #define hc595_ds_pos pc7 //data pin (ds) pin location 42 #define hc595_sh_cp_pos pc5 //shift clock (sh_cp) pin location 40 #define hc595_st_cp_pos pc6 //store clock (st_cp) pin location 41 static const uint8_t pattern[] = { 0b01000000, // 0 0b11101001, // 1 0b00100010, // 2 0b10100000, // 3 0b10001001, // 4 0b10000100, // 5 0b00000100, // 6 0b11100001, // 7 0b00000000, // 8 0b10000000, // 9 0b11101111}; // blank void shiftinit() { //make data(ds), shift clock (sh_cp), store clock (st_cp) lines output hc595_ddr|=((1<<hc595_sh_cp_pos)|(1<<hc595_st_cp_pos)|(1<<hc595_ds_pos)); } #define hc595datahigh() (hc595_port|=(1<<hc595_ds_pos)) #define hc595datalow() (hc595_port&=(~(1<<hc595_ds_pos))) void sendspidata(char data) { for(int8_t i=0;i<8;i++) { hc595_port|=(1<<hc595_sh_cp_pos); //high if(data & 0b10000000) { //msb 1 output high hc595datahigh(); } else { //msb 0 output high hc595datalow(); } hc595_port&=(~(1<<hc595_sh_cp_pos));//low data=data<<1; } } int main(void) { shiftinit(); hc595_port&=(~(1<<hc595_sh_cp_pos));//low hc595_port&=(~(1<<hc595_st_cp_pos));//low while(1) { hc595_port|=(1<<hc595_st_cp_pos);//high sendspidatav2(pattern[7]); //write data shift register sendspidata(pattern[0]); //write data shift register hc595_port&=(~(1<<hc595_st_cp_pos));//low } } when send 7 , 0 (11100001 01000000) receive in 2 registers 74hc595 (11100000 01000001) data not same. nb: bit in position 4 "11100001" ignored it's bp in 7 segment.
where problem? think problem in test if(data & 0b10000000).
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