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feat: Filter RPM jitter caused by single pulse drops

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Tanner Collin (aider)
2025-06-05 11:24:16 -06:00
parent 1f1b379cc2
commit 135537ec2f
1 changed files with 35 additions and 1 deletions
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tach/tach.ino
+34
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@@ -16,6 +16,10 @@ volatile unsigned long g_isr_pulse_count_total = 0; // ISR increments this conti
unsigned long g_main_last_pulse_count_snapshot = 0; // Main loop stores previous snapshot here
unsigned long last_measurement_time = 0;
// --- RPM Display Filtering Variables ---
int g_rpm_value_on_display = 0; // Stores the last RPM value shown on the 7-segment display by the loop
bool g_is_first_rpm_calc_in_loop = true; // Flag to handle the first RPM calculation
// --- Interrupt Service Routine (ISR) ---
void count_pulse() {
g_isr_pulse_count_total++;
@@ -76,7 +80,37 @@ void loop() {
}
int rpm = (int)rpm_float;
// RPM Filtering Logic
if (g_is_first_rpm_calc_in_loop) {
show(rpm);
g_rpm_value_on_display = rpm;
g_is_first_rpm_calc_in_loop = false;
} else {
if (rpm == 0 && g_rpm_value_on_display != 0) {
// If RPM is actually zero, update the display to show zero
show(rpm);
g_rpm_value_on_display = rpm;
} else if (rpm != 0) { // Apply jitter filter only if current rpm is not zero
float rpm_float_if_one_more_pulse = 0.0;
if (actual_elapsed_time > 0) { // Avoid division by zero
rpm_float_if_one_more_pulse = ( (float)(collected_pulses + 1) / PULSES_PER_REVOLUTION ) * (60000.0 / actual_elapsed_time);
}
int rpm_if_one_more_pulse = (int)rpm_float_if_one_more_pulse;
// Check for the specific 1-pulse drop jitter
if (rpm < g_rpm_value_on_display && rpm_if_one_more_pulse == g_rpm_value_on_display) {
// Jitter detected (e.g., displayed 6000, current calc is 5925, but 5925 with +1 pulse would be 6000)
// Do not update the display; keep showing g_rpm_value_on_display.
Serial.print("Filtered (jitter) RPM: "); Serial.print(rpm);
Serial.print(" -> Kept displaying: "); Serial.println(g_rpm_value_on_display);
} else {
// Not a jitter, or a rise, or a larger drop. Update display.
show(rpm);
g_rpm_value_on_display = rpm;
}
}
// If rpm is 0 and g_rpm_value_on_display is already 0, do nothing to avoid redundant show(0)
}
// Debugging output
Serial.print("Pulses: "); Serial.print(collected_pulses);