/****************************************************************************** HardwareRNG1.c Makes RNG serial bytes from 50Hz mains Copyright RomanBlack, 15 Aug 2012 (see schematic at www.RomanBlack.com/HardRNG/HardRNG.htm) Compiler; MikroC for PIC PIC 16F628A, 20MHz HSOSC, xtal or resonator both OK. PIC Pins; RA0 = input, comparator1, detecting 100Hz mains (rectified full wave) RA2 = PIC internal Vref for comparators, connects to 47uF tant cap RA3 connected to RB3 = comp1 output connected to CCP1 capture input RB2 = output, USART TX, serial data out to PC RB7 = output, LED indicates "data good" flashes once per second PIC Config setup; BODEN_OFF, BOREN_OFF, PWRTE_ON, WDT_OFF, LVP_OFF, MCLRE_OFF, HS_OSC ******************************************************************************/ #define MAINSFREQ 50 // set this number to match your mains; 50Hz or 60Hz #define MAINSPERIOD (2500000 / MAINSFREQ) // don't change these 3 defines #define MAINSPERIODMIN ((MAINSPERIOD * 96) / 100) // -4% #define MAINSPERIODMAX ((MAINSPERIOD * 104) / 100) // +4% // global vars unsigned int capture_new absolute 0x20; // 16bit period CCP1 capture unsigned char capture_new_lo absolute 0x20; // overloaded to allow each byte access unsigned char capture_new_hi absolute 0x21; unsigned int capture_last; // also for capture measuring unsigned int period16; // " unsigned int timeout; // for detecting debounce timed out unsigned char deb; // debounce unsigned char mainsgood; // count of how many good mains cycles unsigned char flashcount; // sequencing LED flash once per second unsigned char tbyte; // temp byte for bit processing unsigned char serbyte; // holds serial byte to transmit unsigned char serbitcount; // counts bits until serial byte full unsigned char shiftA[6]; // two shift registers used in RNG unsigned char shiftB[6]; //============================================================================= // TIMER_DELAY_20uS //============================================================================= void timer_delay_20uS(void) { //------------------------------------------------------- // This uses TMR0 to make a delay of exactly 20uS, and the // delay is cyclic, so it syncs to 20uS timer periods and // negates dead time from other loops etc. // Since TMR0 runs at 5MHz, a 20uS delay is 100 TMR0 counts. //------------------------------------------------------- while(!INTCON.T0IF) continue; // wait here for TMR0 overflow INTCON.T0IF = 0; // clear overflow flag TMR0 -= (100-3); // set TMR0 to overflow in 100 counts time // (note! there is a 3 count latency) timeout++; // used to detect mains fail timed-out } //----------------------------------------------------------------------------- //============================================================================= // STOP_OUTPUT //============================================================================= void stop_output(void) { //------------------------------------------------------- // this shuts down the RNG process and resets everything ready // so when mains has tested good again it can restart later. //------------------------------------------------------- mainsgood = 0; // start re-testing mains from scratch serbitcount = 0; // clear all serial bit data, to start again PORTB.F7 = 0; // LED off, flashcount = 0; // and LED flash sequence cleared too timeout = 0; // reset timeout ready to restart } //----------------------------------------------------------------------------- //============================================================================= // MAIN //============================================================================= void main(void) { //------------------------------------------------------- // Setup PIC 16F628A CMCON = 0b00011110; // comps ON, internal Vref, RA0 in, RA3 out, comp1 inverted VRCON = 0b11100101; // CVref ON, low range, 1.04v, Vref output on RA2 PORTA = 0b00000000; // TRISA = 0b00010101; // RA0 comp1 in, RA3 comp1 out, RA2 Vref PORTB = 0b00000000; // TRISB = 0b00001000; // RB3 is CCP1 in, RB2 is USART TX out, RB7 LED out OPTION_REG = 0b10001000; // PORTB pullups disabled, TMR0 at 1:1 prescaler // setup TMR1 and CCP1 to capture the mains pulse T1CON = 0b00000001; // TMR1 ON, 1:1 prescale (5MHz) CCP1CON = 0b00000101; // capture, every rising edge //------------------------------------------------------- // prepare all vars etc ready start RNG later stop_output(); // setup USART at baudrate Usart_Init(9600); //------------------------------------------------------- // loop and output RNG data from USART while(1) { //--------------------------------------------- // NOTE! each loop should be one mains half-cycle //--------------------------------------------- // debounce, first wait for mains to be high for at least 4000uS (4mS) timeout = 0; for(deb=0; deb<200; deb++) // 200 loops of 20uS = 4000uS { timer_delay_20uS(); if(!PORTB.F3) deb = 0; if(timeout >= 500) stop_output(); // timeout error after 10mS } //--------------------------------------------- // debounce, wait for mains to be low for at least 200uS timeout = 0; for(deb=0; deb<10; deb++) // 20 loops of 20uS = 200uS { timer_delay_20uS(); if(PORTB.F3) deb = 0; if(timeout >= 500) stop_output(); // timeout error after 10mS } //--------------------------------------------- // now mains is synced, wait for capture of mains pulse on first / edge timeout = 0; PIR1.CCP1IF = 0; while(!PIR1.CCP1IF) // wait for CCP1 capture! { timer_delay_20uS(); if(timeout >= 100) stop_output(); // timeout error after 2mS } //--------------------------------------------- // gets here after a capture! so test if period is within // the right range, if it is we assume mains freq is good. capture_new_lo = CCPR1L; // get the new 16bit capture value capture_new_hi = CCPR1H; period16 = (capture_new - capture_last); // calculate 16bit period between captures capture_last = capture_new; // save value to get period next time // now the period is in period16, so test it for valid range if(period16 < MAINSPERIODMIN || period16 > MAINSPERIODMAX) // if NOT valid { stop_output(); } else // else mains seems to be good! { mainsgood++; // count good mains cycles if(mainsgood > 200) mainsgood = 200; // and limit max count } //--------------------------------------------- // If mains is reliable, ie has been good for at least 100 cycles, // then start filling the shift registers. if(mainsgood >= 100) { // shift the bit1 into shift register A shiftA[5] <<= 1; shiftA[5].F0 = shiftA[4].F7; shiftA[4] <<= 1; shiftA[4].F0 = shiftA[3].F7; shiftA[3] <<= 1; shiftA[3].F0 = shiftA[2].F7; shiftA[2] <<= 1; shiftA[2].F0 = shiftA[1].F7; shiftA[1] <<= 1; shiftA[1].F0 = shiftA[0].F7; shiftA[0] <<= 1; shiftA[0].F0 = capture_new_lo.F1; // shift the bit2 into shift register B shiftB[3] <<= 1; shiftB[3].F0 = shiftB[2].F7; shiftB[2] <<= 1; shiftB[2].F0 = shiftB[1].F7; shiftB[1] <<= 1; shiftB[1].F0 = shiftB[0].F7; shiftB[0] <<= 1; shiftB[0].F0 = capture_new_lo.F2; } //--------------------------------------------- // if mains is reliable and shift registers full, then process // RNG data and send it out serial port, and operate "data good" LED. if(mainsgood > (100+47)) { // XOR the 3 bits; shiftA bit47, shiftB bit29, and new bit0 tbyte.F0 = capture_new_lo.F0; // get new bit0 into temp byte bit0 if(shiftA[5].F7) tbyte ^= 0x01; // XOR shiftA bit 47 if(shiftB[3].F5) tbyte ^= 0x01; // XOR shiftB bit 29 // add to final shift register to output each 8bits as a byte serbyte <<= 1; // left shift 1 bit serbyte.F0 = tbyte.F0; // and add in new RNG bit serbitcount++; if(serbitcount >= 8) { serbitcount = 0; Usart_Write(serbyte); // output the RNG byte to serial } // flash the "data good" LED, exactly once per second at 50% duty cycle flashcount++; if(flashcount >= (MAINSFREQ*2)) flashcount = 0; if(flashcount < MAINSFREQ) PORTB.F7 = 1; // LED on else PORTB.F7 = 0; // or off } //--------------------------------------------- } } //-----------------------------------------------------------------------------