fix: Improve pulse counting with continuous ISR and diff

tach/tach.ino

@@ -12,12 +12,13 @@ Adafruit_7segment matrix = Adafruit_7segment();
 
 // --- Tachometer variables ---
 const int TACH_INTERRUPT_PIN = A0; // Or any other digital pin capable of interrupts
-volatile unsigned long pulse_count = 0;
+volatile unsigned long g_isr_pulse_count_total = 0; // ISR increments this continuously
+unsigned long g_main_last_pulse_count_snapshot = 0; // Main loop stores previous snapshot here
 unsigned long last_measurement_time = 0;
 
 // --- Interrupt Service Routine (ISR) ---
 void count_pulse() {
-  pulse_count++;
+  g_isr_pulse_count_total++;
 }
 
 void show(int num) {
@@ -50,10 +51,18 @@ void loop() {
   unsigned long current_time = millis();
 
   if (current_time - last_measurement_time >= MEASUREMENT_PERIOD_MS) {
-    detachInterrupt(digitalPinToInterrupt(TACH_INTERRUPT_PIN));
-    unsigned long collected_pulses = pulse_count;
-    pulse_count = 0;
-    attachInterrupt(digitalPinToInterrupt(TACH_INTERRUPT_PIN), count_pulse, RISING);
+    unsigned long current_total_snapshot;
+
+    // Atomically read the total pulse count
+    noInterrupts();
+    current_total_snapshot = g_isr_pulse_count_total;
+    interrupts();
+
+    // Calculate pulses collected during this interval
+    unsigned long collected_pulses = current_total_snapshot - g_main_last_pulse_count_snapshot;
+    
+    // Store the current total snapshot for the next interval's calculation
+    g_main_last_pulse_count_snapshot = current_total_snapshot;
 
     // Calculate RPM
     // RPM = (pulses / pulses_per_revolution) / (measurement_period_ms / 1000 / 60)