void set_speed(struct wave * const wave, midi_value_t speed)
{
// Scale range from [0..127] to [15..300] bpm
fixed_t freq = fixed_from_int(speed);
freq /= 127;
freq *= 285;
freq += fixed_from_int(15);
freq /= 60;
set_frequency(wave, freq);
}
void tap_tempo_task(void)
{
static uint8_t taps = 0;
static uint8_t buffer_index = 0;
// Increment counter
static uint16_t counter = 0;
++counter;
if (!tap_arrived) {
if (counter < 400) {
return;
}
// Reset after timeout
set_led(LED_RED, false);
counter = 0;
taps = 0;
buffer_index = 0;
return;
}
tap_arrived = false;
// Increment tap counter to buffer size
if (taps < TAP_TEMPO_BUFFER_SIZE) {
++taps;
}
if (taps == 1) {
set_led(LED_RED, true);
}
else {
// Register tap interval with cyclic buffer
static fixed_t tap_tempo_buffer[TAP_TEMPO_BUFFER_SIZE] = {0, };
fixed_t tap_frequency = fixed_from_int(TAP_TEMPO_TASK_FREQUENCY) / counter;
tap_tempo_buffer[buffer_index] = tap_frequency;
++buffer_index;
buffer_index %= TAP_TEMPO_BUFFER_SIZE;
// Compute average
fixed_t average = 0;
for (int i=0; i<taps; i++) {
average += tap_tempo_buffer[i];
}
average /= taps;
// Set wave frequency
set_frequency(tap_tempo_wave, average);
}
// Reset counter
counter = 0;
}
void Scan_Samples(void){
fixed ybox[7]; // array box car derivative
s16 bin; // index into peak height array
fixed dt, tau, *yp0, *yp1, y, y_i;
fixed threshold; // trigger level for leading edge
fixed deriv;
fixed alpha, beta, gamma, peak;
s16 i;
configurations *cp = &configuration;
ADC_Stop();
tail = head = Get_Scan_Pos(); // get current absolute position in adc buffer
/*
if(cp->sig_filter){
// Set up Butterworth low pass filter
dt = FIXED_HALF; // sample time 0.5 uS
tau = fixed_from_int(cp->sig_filter); // filter time in uS
alpha = fixed_div(dt, tau + dt);
}
*/
ADC_Start();
while(TRUE){
if(tail == head){
head = Get_Scan_Pos();
// recalculate filter elements in case changed
/*
if(cp->sig_filter){
// Set up Butterworth low pass filter in case of changes
dt = FIXED_HALF; // sample time 0.5 uS
tau = fixed_from_int(cp->sig_filter); // filter time in uS
alpha = fixed_div(dt, tau + dt);
}
*/
}
if(tail == head)
continue;
// track live time
if(samp_cntr++ >= SAMP_PER_MS){
live_time++;
samp_cntr = 0;
}
// get new value, adjust for zero and inversion at same time
y = fixed_from_int(zero - scan_buffer[tail++]);
if(tail >= SCAN_BUFFER_SZ){
tail = 0;
}
// filter signal if needed
/*
if(cp->sig_filter){
// Butterworth low pass filter
y = *yp0 + fixed_mul(alpha, (y - *yp0));
}
*/
// shift the boxcar window and find derivative
yp0 =&ybox[0];
yp1 = &ybox[1];
for(i = 6; i > 0; i--){ // last box slot gets new y value
*yp0++ = *yp1++;
}
*yp0 = y; // place latest sample in end of boxcar
// compute the derivative
deriv = 0;
yp0 =&ybox[0];
deriv -= *yp0++;
deriv -= *yp0++;
alpha = *yp0;
deriv -= *yp0++;
beta = *yp0++;
gamma = *yp0;
deriv += *yp0++;
deriv += *yp0++;
deriv += *yp0++;
// process depending on state
switch(scan_state){
case RESTART:
scan_state = LEADING;
//cp->scope_valid = FALSE;
break;
case LEADING:
if(cp->sig_type == PULSE_POS && deriv > cp->sig_dvdt_lim){
scan_state = PEAK;
break;
}
if(cp->sig_type == PULSE_NEG && deriv < cp->sig_dvdt_lim){
scan_state = PEAK;
break;
}
// if no pulse then check the zero
avg_zero = (avg_zero * 20 + y)/21;
break;
case PEAK:
// reverse derivative indicates peak
if(cp->sig_type == PULSE_POS && deriv < 0){
scan_state = TAIL;
}
if(cp->sig_type == PULSE_NEG && deriv > 0){
scan_state = TAIL;
}
if(scan_state == TAIL){
// handle gaussian approximation if enabled
if(cp->sig_gaussian){
// p = ((a - g)/(a -2b + g))/2 = position of peak
peak = (fixed_div((alpha - gamma),(alpha - (2 * beta) + gamma))) / 2;
// y(p) = b - ((a - g) * p)/4 = peak value
peak = beta - (fixed_mul((alpha - gamma), peak) / 4);
} else {
peak = (alpha + beta + gamma) / 3;
}
if(cp->sig_type == PULSE_NEG){
peak = -peak;
}
// peak now always positive
if( peak > cp->sig_lo_lim && peak < cp->sig_hi_lim){
bin = fixed_to_int(peak);
pulse_height[bin]++; // increment count in spectrum array
cur_cnt++;
// handle rate meter beeping
if(cp->rate_beep && !alarm_on){
Beep(BEEP_500Hz, 10);
}
}
}
break;
case TAIL:
// find where curve turns back to baseline
if(cp->sig_type == PULSE_POS && deriv >= 0){
scan_state = LEADING;
}
if(cp->sig_type == PULSE_NEG && deriv <= 0){
scan_state = LEADING;
}
break;
} // switch(scan_state)
} // while ring buffer not empty
}
void set_frequency(struct wave * const wave, fixed_t frequency)
{
wave->settings.frequency = frequency;
const fixed_t max_frequency = fixed_from_int(F_TASK_FAST/(2*WAVE_STEPS));
wave->state.speed_prescaler = fixed_to_int(fixed_div(max_frequency, wave->settings.frequency));
}