brymen_bm869s_ir_cable

main.c (7650B)

---

 /*
  * all the relevant parts of this code have been shamelessly taken and adapted
  * from here:
  *
  * https://www.eevblog.com/forum/testgear/brymen-ir-connection-protocol-anyone-sniffed-it-yet/msg874805/#msg874805
  *
  * All credit goes to eevblog forum user 'jesuscf'. I just adapted to AVR C for
  * the ATTiny85
  */
 
 #include <avr/io.h>
 #include <util/delay.h>
 
 #include <bm869s.h>
 #include <avr305.h>
 
 #define HIGH 1
 #define LOW 0
 #define IRTX PB3
 #define IRRX PB2
 
 /* Storage for the information received from the multimeter */
 #define BM_PBYTES 20 /* 16 bytes with data and 4 bytes with other information */
 unsigned char bm[BM_PBYTES];
 
 void digitalWrite(int pin, int state)
 {
     if (state == HIGH) {
         PORTB |= (1 << pin);
     } else {
         PORTB &= ~(1 << pin);
     }
 }
 
 unsigned char digitalRead(int pin)
 {
     return (PINB & (1 << pin));
 }
 
 /* Reads a byte from the multimeter */
 unsigned char getByte(void)
 {
     unsigned char result, mask;
 
     /* bit by bit check (using shift mask)
      * clock --> check --> "unclock" */
     for (mask = 1, result = 0; mask != 0; mask <<= 1) {
         digitalWrite(IRTX, HIGH);
         _delay_us(250);
 
         /* checking on low instead of high, so maybe we can reuse
          * some work done on eevblog forum */
         if (digitalRead(IRRX) == LOW) result |= mask;
 
         digitalWrite(IRTX, LOW);
         _delay_us(250);
     }
     return result;
 }
 
 /* Reads 20 bytes from the multimeter */
 int readBM689s(void)
 {
     unsigned int timeout;
     unsigned char j;
 
     /* wait in case dmm is transmitting already */
     while (digitalRead(IRRX) == HIGH);
 
     /* init communication 10ms pulse */
     digitalWrite(IRTX, HIGH);
     _delay_ms(10);
     digitalWrite(IRTX, LOW);
 
     /* wait for dmm response */
     timeout = 0;
     while (digitalRead(IRRX) == LOW) {
         _delay_ms(1);
         timeout++;
         if (timeout > 1000) break;
     }
     /* if we did not reach timeout, get 20 bytes. */
     if (timeout <= 1000) {
         for (j = 0; j < BM_PBYTES; j++) bm[j] = getByte();
         return 1;
     }
     return 0;
 }
 
 /* Converts the digits information received into ASCII characters */
 char Decode_7seg(unsigned char val)
 {
     switch (val & 0xfe) {
         case LETTER_C: return'C'; break;
         case LETTER_d: return'd'; break;
         case LETTER_F: return'F'; break;
         case LETTER_i: return'i'; break;
         case LETTER_L: return'L'; break;
         case LETTER_o: return'o'; break;
         case BLANK:    return' '; break;
         case DASH:     return'-'; break;
         case NUMBER_0: return'0'; break;
         case NUMBER_1: return'1'; break;
         case NUMBER_2: return'2'; break;
         case NUMBER_3: return'3'; break;
         case NUMBER_4: return'4'; break;
         case NUMBER_5: return'5'; break;
         case NUMBER_6: return'6'; break;
         case NUMBER_7: return'7'; break;
         case NUMBER_8: return'8'; break;
         case NUMBER_9: return'9'; break;
         default:
             return'?';
             break;
     }
 }
 
 /* Sends via serial port whatever was read and decoded from the multimeter for
  * the main display */
 void Send_Disp1(void)
 {
     char c;
 
     /* + or - sign */
     if (((bm[14] & Hz_1) == 0) && ((bm[14] & DUTY) == 0)
             && ((bm[14] & OHM) == 0) && ((bm[13] & FARAD) == 0)) {
         printc(bm[1]&negative_1 ? '-' : '+');
     }
 
     /* main digits */
     printc(Decode_7seg(bm[2]));
     if (bm[3] & seg_p) printc('.');
     printc(Decode_7seg(bm[3]));
     if (bm[4] & seg_p) printc('.');
     printc(Decode_7seg(bm[4]));
     if (bm[5] & seg_p) printc('.');
     printc(Decode_7seg(bm[5]));
     if (bm[6] & seg_p) printc('.');
     printc(Decode_7seg(bm[6]));
     c = Decode_7seg(bm[7]);
     if (c != ' ') printc(c);
 
     /* Display the units of voltage or current */
     if ((bm[7] & V_1) || (bm[13] & A_1)) {
         if ((bm[14] & m_1) || (bm[14] & u_1)) {
             printc('E');
             printc('-');
             printc((bm[14] & m_1) ? '3' : '6');
         }
         printc(' ');
         if (bm[7] & V_1)
             printc('V');
         else
             printc('A');
         if (bm[0] & DC) {
             if (bm[1] & AC_1) {
                 printc('R');
                 printc('M');
                 printc('S');
             } else {
                 printc('D');
                 printc('C');
             }
         } else if (bm[1] & AC_1) {
             printc('A');
             printc('C');
         }
     }
 
     /* Frequency */
     if (bm[14] & Hz_1) {
         if ((bm[14] & k_1) || (bm[14] & M_1)) {
             printc('E');
             printc('+');
             if (bm[14] & k_1)
                 printc('3');
             else
                 printc('6');
         }
         printc(' ');
         printc('H');
         printc('z');
     }
 
     /* Duty cycle */
     if (bm[14] & DUTY) {
         printc(' ');
         printc('D');
         printc('%');
     }
 
     /* dB */
     if (bm[14] & dB) {
         printc(' ');
         printc('d');
         printc('B');
         if (bm[14] & m_1) printc('m');
     }
 
     /* Resistance */
     if (bm[14] & OHM) {
         if ((bm[14] & k_1) || (bm[14] & M_1)) {
             printc('E');
             printc('+');
             if (bm[14] & k_1)
                 printc('3');
             else
                 printc('6');
         }
         printc(' ');
         printc('O');
         printc('H');
         printc('M');
     }
 
     /* Capacitance */
     if (bm[13] & FARAD) {
         if ((bm[13] & n) || (bm[14] & u_1) || (bm[14] & m_1)) {
             printc('E');
             printc('-');
             if (bm[13] & n)        printc('9');
             else if (bm[14] & u_1) printc('6');
             else if (bm[14] & m_1) printc('3');
         }
         printc(' ');
         printc('F');
     }
 }
 
 /* Sends via serial port whatever was read and decoded from the multimeter for
  * the second display */
 void Send_Disp2(void)
 {
     char c;
 
     c = Decode_7seg(bm[9]);
 
     if (c != ' ') {
         printc(bm[8]&negative_2 ? '-' : '+');
         printc(Decode_7seg(bm[9]));
         if (bm[10] & seg_p) printc('.');
         printc(Decode_7seg(bm[10]));
         if (bm[11] & seg_p) printc('.');
         printc(Decode_7seg(bm[11]));
         if (bm[12] & seg_p) printc('.');
         printc(Decode_7seg(bm[12]));
 
         /* Display the units of voltage or current */
         if ((bm[13] & V_2) || (bm[8] & A_2)) {
             if ((bm[8] & m_2) || (bm[8] & u_2)) {
                 printc('E');
                 printc('-');
                 printc((bm[8] & m_2) ? '3' : '6');
             }
             printc(' ');
             if (bm[13] & V_2)
                 printc('V');
             else
                 printc('A');
             if (bm[8] & AC_2) {
                 printc('A');
                 printc('C');
             } else {
                 printc('D');
                 printc('C');
             }
         }
 
         /* Frequency */
         if (bm[13] & Hz_2) {
             if ((bm[13] & k_2) || (bm[13] & M_2)) {
                 printc('E');
                 printc('+');
                 if (bm[13] & k_2)
                     printc('3');
                 else
                     printc('6');
             }
             printc(' ');
             printc('H');
             printc('z');
         }
     }
 }
 
 int main(void)
 {
     /* Pin initialization */
     DDRB |= (1 << IRTX);         /* port output */
     DDRB &= ~(1 << IRRX);        /* port input */
     PORTB &= ~(1 << IRTX);       /* set output ports to low */
 
     while (1) {
         readBM689s();
         Send_Disp1();
         printc(' ');
         Send_Disp2();
         printc('\r');
         printc('\n');
         _delay_ms(200);
     }
 
     return 0;
 }