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Diffstat (limited to 'test/picc/test.c')
| -rw-r--r-- | test/picc/test.c | 348 |
1 files changed, 348 insertions, 0 deletions
diff --git a/test/picc/test.c b/test/picc/test.c new file mode 100644 index 0000000..5fc2e81 --- /dev/null +++ b/test/picc/test.c @@ -0,0 +1,348 @@ +/* + * level - electronic level using the ADXL202 + * + * This program consists of an interrupt routine that measures the pulse + * width from the ADXL202 and a main routine that updates the dot matrix + * display on the DISPLAY board. + * + * Timer1 and the two Capture/Compare registers are used to measure the + * pulse width. + * + * Use PICCLITE to compile this program for the PIC16F877. + * + * Status: Sept 25, 2003 + * Working. The code is pretty brute force and the resolution isn't + * what I expected. Need to review calculations for angle vs. accel + * (gravity). I determined the zero offsets empirically and hard coded + * them. For coding simplicity I am discarding any measurements where + * the counter overflows during the measurement. + * + * Improvements should include: a method to zero the offsets at + * runtime and increased gain (which probably means going to 16 bit + * values). Also consider filtering the measured values to gain stability. + * Add code to handle counter overflow. + */ + +#include <pic.h> +#include "test.h" + +/* + * bit macros suggested by the PICCLITE manual + */ +#define BITSET(var, bitno) ((var) |= 1 << (bitno)) +#define BITCLR(var, bitno) ((var) &= ~(1 << (bitno))) + + +/* + * pulse with variables + * + * These are set up the measurePW() ISR and read by the main loop + */ +unsigned char PeriodStartX; +unsigned char PeriodEndX; +unsigned char PulseEndX; +unsigned char PulseEndTempX; +unsigned char PWSyncX; + +unsigned char PeriodStartY; +unsigned char PeriodEndY; +unsigned char PulseEndY; +unsigned char PulseEndTempY; +unsigned char PWSyncY; + +/* + * interrupt service routine to measure pulse width + * + * This routine uses the capture facility of the 16F877 to measure the + * period and the pulse width of a signal. This routine has two states + * the first looks for the rising edge of the signal which indicates the + * end of one period and the beginning of the next. The second state + * looks for the falling edge of the signal to determine the pulse + * width. + * + * Only the high 8 bits of the captured time are record. At 20MHz this + * yields a time resolution of approximately 51us. + * + * RC0 and RC1 indicate ISR over-run (in other words the main loop did + * not handle the measured values quickly enough). + */ +void interrupt +measurePW(void) +{ + /* determined which capture register requires service */ + if (CCP1IF == 1) + { + /* CCP1 */ + if ((CCP1CON & 0b00000111) == 0b00000101) + { + /* rising edge- + * record last rise time (period_end -> period_start) + * record last falling time (pulse_end_temp -> pulse_end) + * record this rise time (capture -> period_end) + * set synchronization flag + * change mode to look for falling edge + */ + PeriodStartX = PeriodEndX; + PulseEndX = PulseEndTempX; + PeriodEndX = CCPR1H; + PWSyncX++; + CCP1CON = 0b00000100; + + /* Indicated an ISR over-run if the sync flag was + * not cleared by the main loop + */ + if (PWSyncX > 1) + { + RC0 = 0; + } + } + else /* assume falling edge */ + { + /* falling- + * save this falling time for later + * change mode to look for rising edge + */ + PulseEndTempX = CCPR1H; + CCP1CON = 0b00000101; + } + /* + * clear interrupt flags and return + */ + CCP1IF = 0; + } + else + { + /* CCP2 */ + if ((CCP2CON & 0b00000111) == 0b00000101) + { + /* rising edge- + * record last rise time (period_end -> period_start) + * record last falling time (pulse_end_temp -> pulse_end) + * record this rise time (capture -> period_end) + * set synchronization flag + * change mode to look for falling edge + */ + PeriodStartY = PeriodEndY; + PulseEndY = PulseEndTempY; + PeriodEndY = CCPR2H; + PWSyncY++; + CCP2CON = 0b00000100; + + /* Indicated an ISR over-run if the sync flag was + * not cleared by the main loop + */ + if (PWSyncY > 1) + { + RC3 = 0; + } + } + else /* assume falling edge */ + { + /* falling- + * save this falling time for later + * change mode to look for rising edge + */ + PulseEndTempY = CCPR2H; + CCP2CON = 0b00000101; + } + /* + * clear interrupt flags and return + */ + CCP2IF = 0; + } +} + + +/* + * measure tilt and update dot matrix display + * + * This program uses the times recorded by the measurePW() ISR to + * calculate pulse width. The pulse width is then translated into a tilt + * measurement and finally displayed on the dot matrix display. + */ +void +main(void) +{ + unsigned char periodX = 0; + unsigned char pulseX = 0; + unsigned char periodY = 0; + unsigned char pulseY = 0; + int tiltX; + int tiltY; + + /* + * Setup I/O ports + * RC0 and RC3 outputs, the rest are inputs. + * RA5 output (power to ADXL202) + * Set port C outputs high to turn off the LEDs + */ + TRISC = 0b11110110; + RA5 = 1; + PORTC = 0xff; + + /* + * Setup the I/O ports that control the dot matrix display + */ + TRISA = 0b11000000; + TRISB = 0b11100000; + TRISD = 0b10000000; + ADCON1 = 0x06; /* disable ADC so that port A is digital I/O */ + PORTD = 0; /* turn off all rows */ + PORTB = 0xff; /* turn off all columns */ + PORTA = 0xff; /* turn off all columns */ + + /* configure timer1 + * 1:1 prescale + * Internal clock (Fosc/4) + * Enabled + */ + T1CON = 0b00000001; + + /* + * configure capture registers + * capture on rising edge + */ + CCP1CON = 0b00000101; + CCP2CON = 0b00000101; + + /* + * clear sync flag + */ + PWSyncX = 0; + PWSyncY = 0; + + /* + * enable interrupts + */ + PEIE = 1; + CCP1IE = 1; + CCP2IE = 1; + ei(); + + /* + * main loop + */ + for (;;) + { + /* + * kick watchdog + */ + CLRWDT(); + + if (PWSyncX > 0) + { + /* + * Test for easy calculations + * i.e., no counter roll over during the measurment + */ + if (PeriodEndX > PeriodStartX) + { + if (PulseEndX > PeriodStartX) + { + /* + * no roll over, so proceed + */ + periodX = PeriodEndX - PeriodStartX; + pulseX = PulseEndX - PeriodStartX; + + periodX = (periodX / 2) + 9; /* offset = 9 */ + tiltX = (periodX) - pulseX; + + /* + * turn off all rows and then figure out which row to turn + * on based on the tilt + */ + PORTD = 0; + if (tiltX < -5) + { + RD6 = 1; + } + else if (tiltX < -4) + { + RD5 = 1; + } + else if (tiltX < -2) + { + RD4 = 1; + } + else if (tiltX > 5) + { + RD0 = 1; + } + else if (tiltX > 4) + { + RD1 = 1; + } + else if (tiltX > 2) + { + RD2 = 1; + } + else + { + RD3 = 1; + } + } + } + PWSyncX = 0; + } + + if (PWSyncY > 0) + { + /* + * Test for easy calculations + * i.e., no counter roll over during the measurment + */ + if (PeriodEndY > PeriodStartY) + { + if (PulseEndY > PeriodStartY) + { + /* + * no roll over, so proceed + */ + periodY = PeriodEndY - PeriodStartY; + pulseY = PulseEndY - PeriodStartY; + + periodY = (periodY / 2) - 1; /* offset = -1 */ + tiltY = (periodY) - pulseY; + + /* + * turn off all columns then figure out which column + * to turn on based on the tilt + */ + PORTA = PORTA | 0b00111111; + PORTB = PORTB | 0b00011111; + if (tiltY < -5) + { + RB1 = 0; + } + else if (tiltY < -4) + { + RB0 = 0; + } + else if (tiltY < -2) + { + RA4 = 0; + } + else if (tiltY > 5) + { + RA0 = 0; + } + else if (tiltY > 4) + { + RA1 = 0; + } + else if (tiltY > 2) + { + RA2 = 0; + } + else + { + RA3 = 0; + } + } + } + PWSyncY = 0; + } + } +} + |