button: add basic button functionalities

- Provided a way to set handler for each button one-press/long-press
- Debouncing with RC filter and Schmitt trigger

1 files changed, 89 insertions, 0 deletions

diff --git a/src/button.c b/src/button.c
new file mode 100644
index 0000000..6adb495
--- /dev/null
+++ b/src/button.c
@@ -0,0 +1,89 @@
+#include "button.h"
+
+#define DEBOUNCE_HIGH_THRES (200) // 0-255
+#define DEBOUNCE_LOW_THRES  (55)  // 0-255
+#define LONGPRESS_THRES     (25)  // Hz
+#define BUTTON_SCAN_FREQ    (50)  // Hz
+
+static volatile void (*onePressHandler[KEY_INDEX])(void) = { NULL };
+static volatile void (*longPressHandler[KEY_INDEX])(void) = { NULL };
+
+void btn_init()
+{
+	GPIOA_ModeCfg(KEY1_PIN, GPIO_ModeIN_PD);
+	GPIOB_ModeCfg(KEY2_PIN, GPIO_ModeIN_PU);
+
+	TMR3_TimerInit(FREQ_SYS/BUTTON_SCAN_FREQ);
+	TMR3_ITCfg(ENABLE, TMR0_3_IT_CYC_END);
+	PFIC_EnableIRQ(TMR3_IRQn);
+}
+
+void btn_onOnePress(int key, void (*handler)(void))
+{
+	if (key >= KEY_INDEX) return;
+	onePressHandler[key] = handler;
+}
+
+void btn_onLongPress(int key, void (*handler)(void))
+{
+	if (key >= KEY_INDEX) return;
+	longPressHandler[key] = handler;
+}
+
+__HIGH_CODE
+static int debounce(int key, int is_press)
+{
+	static int y[KEY_INDEX], flag[KEY_INDEX];
+	if (key >= KEY_INDEX) return 0;
+	
+	// RC filter
+	y[key] -=  y[key] >> 2;
+	y[key] += is_press ? 0x3F : 0;
+
+	// Schmitt trigger
+	if ((y[key] > DEBOUNCE_HIGH_THRES) && (flag[key] == 0))
+		flag[key] = 1;
+	if ((y[key] < DEBOUNCE_LOW_THRES) && (flag[key] == 1))
+		flag[key] = 0;
+
+	return flag[key];
+}
+
+__HIGH_CODE
+static void check(int k)
+{
+	static int hold[KEY_INDEX], is_longpress[KEY_INDEX];
+	if (k >= KEY_INDEX) return; // TODO: assert instead
+
+	if (debounce(k, isPressed(k))) {
+		hold[k]++;
+		if (hold[k] >= LONGPRESS_THRES && is_longpress[k] == 0) {
+			is_longpress[k] = 1;
+			if (longPressHandler[k]) longPressHandler[k]();
+		}
+	} else {
+		if (hold[k] > 0 && hold[k] < LONGPRESS_THRES) {
+			if (onePressHandler[k]) onePressHandler[k]();
+		}
+		is_longpress[k] = 0;
+		hold[k] = 0;
+	}
+}
+
+__HIGH_CODE
+static void check_keys()
+{
+	for (int k=0; k<KEY_INDEX; k++) {
+		check(k);
+	}
+}
+
+__INTERRUPT
+__HIGH_CODE
+void TMR3_IRQHandler(void)
+{
+	if (TMR3_GetITFlag(TMR0_3_IT_CYC_END)) {		
+		check_keys();
+		TMR3_ClearITFlag(TMR0_3_IT_CYC_END);
+	}
+}