From 9bcbd9f4b11d736334604a6a9b9c79f731a4753d Mon Sep 17 00:00:00 2001
From: rkcf <rkcf@rkcf.me>
Date: Sat, 28 Jan 2023 13:40:44 -0600
Subject: [PATCH] add in code for button debouncing

---
 main/esp32-sequencer.c | 49 +++++++++++++++++++++++++++++++++++-------
 1 file changed, 41 insertions(+), 8 deletions(-)

diff --git a/main/esp32-sequencer.c b/main/esp32-sequencer.c
index 1b90ff1..5f6a878 100644
--- a/main/esp32-sequencer.c
+++ b/main/esp32-sequencer.c
@@ -34,8 +34,12 @@ static QueueHandle_t control_event_queue = NULL;
 #define LEDC_GATE_OUT (6)
 
 /* Timers */
-gptimer_handle_t tap_tempo_timer = NULL;
-gptimer_handle_t gate_timer = NULL;
+static gptimer_handle_t tap_tempo_timer = NULL;
+static gptimer_handle_t gate_timer = NULL;
+
+static const uint16_t DEBOUNCE_TIMEOUT = 20; // polling period length when debouncing in ms
+static uint64_t debounce_time = 0; // system time of last intterupt
+static uint8_t btn_state = 1; // state of gpio last recorded
 
 static const uint32_t DEFAULT_BPM = 120;
 
@@ -71,20 +75,49 @@ static void mutate_seq(uint8_t *sequence) {
   }
 }
 
+/* Handle tap tempo button presses */
+static void tap_tempo_handler(){
+  // check the count to see if we have already started the timer
+  uint64_t count;
+  ESP_ERROR_CHECK(gptimer_get_raw_count(tap_tempo_timer, &count));
+  if (count == 0) { // the timer hasn't started yet
+    ESP_ERROR_CHECK(gptimer_start(tap_tempo_timer));
+    ESP_LOGI(TAG, "Starting tap tempo monitoring");
+  } else { // stop the timer and calc bpm
+    ESP_ERROR_CHECK(gptimer_stop(tap_tempo_timer));
+    ESP_LOGI(TAG, "Stopping tap tempo monitoring at %" PRIu64 "µs", count);
+  }
+}
+
 static void IRAM_ATTR gpio_isr_handler(void* arg) {
+  debounce_time = xTaskGetTickCount(); // set time of interrupt
   uint32_t gpio_num = (uint32_t)arg;
+  btn_state = gpio_get_level(gpio_num); // set state
   xQueueSendFromISR(control_event_queue, &gpio_num, NULL);
 }
 
 static void control_event_handler(void* arg) {
   uint32_t gpio_num;
+  uint8_t last_btn_state;
+  uint64_t last_debounce_time;
   while (1) {
-    if(xQueueReceive(control_event_queue, &gpio_num, portMAX_DELAY)) {
-      ESP_LOGI(TAG, "Handling control from GPIO %" PRIu32 , gpio_num);
-      switch (gpio_num) {
-      case GPIO_MUTATE_BTN:
-        mutate_seq(sequence);
-        break;
+    // save these so we can make comparisons
+    last_btn_state = btn_state;
+    last_debounce_time = debounce_time;
+    uint8_t current_state = gpio_get_level(gpio_num);
+    if (xQueueReceive(control_event_queue, &gpio_num, portMAX_DELAY)) {
+      // Check if interrupt triggered stays the same for long enough
+      if ((current_state == last_btn_state) &&
+          (xTaskGetTickCount() - last_debounce_time > DEBOUNCE_TIMEOUT)) {
+        ESP_LOGI(TAG, "Handling control from GPIO %" PRIu32, gpio_num);
+        switch (gpio_num) {
+        case GPIO_MUTATE_BTN:
+          mutate_seq(sequence);
+          break;
+        case GPIO_TAP_TEMPO_BTN:
+          tap_tempo_handler();
+          break;
+        }
       }
     }
   }