From 32e68c33b476042c7dc52fefc3a685b7cc90b429 Mon Sep 17 00:00:00 2001
From: Alex Voinea <voinea.dragos.alexandru@gmail.com>
Date: Sun, 23 Apr 2023 23:21:24 +0200
Subject: [PATCH] lcd encoder: use lookup table

Also handle the scenario where the encoder moves two steps in a single lcd_buttons_update cycle.

Flash: -46B
SRAM: 0B
---
 Firmware/lcd.cpp | 30 ++++++++++++++++--------------
 Firmware/lcd.h   |  8 --------
 2 files changed, 16 insertions(+), 22 deletions(-)

diff --git a/Firmware/lcd.cpp b/Firmware/lcd.cpp
index 36e58eb59..e6a2d4c40 100644
--- a/Firmware/lcd.cpp
+++ b/Firmware/lcd.cpp
@@ -751,7 +751,6 @@ void lcd_buttons_update(void)
 {
     static uint8_t lcd_long_press_active = 0;
     static uint8_t lcd_button_pressed = 0;
-    static uint8_t lcd_encoder_bits = 0;
     if (READ(BTN_ENC) == 0)
     { //button is pressed
         if (buttonBlanking.expired_cont(BUTTON_BLANKING_TIME)) {
@@ -784,24 +783,27 @@ void lcd_buttons_update(void)
     }
 
     //manage encoder rotation
-    #define ENCODER_SPIN(_E1, _E2) switch (lcd_encoder_bits) { case _E1: lcd_encoder_diff++; break; case _E2: lcd_encoder_diff--; }
-    uint8_t enc = 0;
-    if (READ(BTN_EN1) == 0) enc |= B01;
-    if (READ(BTN_EN2) == 0) enc |= B10;
-    if (enc != lcd_encoder_bits)
+	static const int8_t encrot_table[] PROGMEM = {
+		0, -1, 1, 2,
+		1, 0, 2, -1,
+		-1, 2, 0, 1,
+		2, 1, -1, 0,
+	};
+
+	static uint8_t enc_bits_old = 0;
+	uint8_t enc_bits = 0;
+    if (!READ(BTN_EN1)) enc_bits |= _BV(0);
+    if (!READ(BTN_EN2)) enc_bits |= _BV(1);
+    
+	if (enc_bits != enc_bits_old)
     {
-        switch (enc)
-        {
-            case encrot0: ENCODER_SPIN(encrot3, encrot1); break;
-            case encrot1: ENCODER_SPIN(encrot0, encrot2); break;
-            case encrot2: ENCODER_SPIN(encrot1, encrot3); break;
-            case encrot3: ENCODER_SPIN(encrot2, encrot0); break;
-        }
+		int8_t newDiff = pgm_read_byte(&encrot_table[(enc_bits_old << 2) | enc_bits]);
+		lcd_encoder_diff += newDiff;
 
         if (abs(lcd_encoder_diff) >= ENCODER_PULSES_PER_STEP) {
             lcd_backlight_wake_trigger = true; // flag event, knob rotated
         }
-        lcd_encoder_bits = enc;
+        enc_bits_old = enc_bits;
     }
 }
 
diff --git a/Firmware/lcd.h b/Firmware/lcd.h
index 13377da70..2a4682739 100644
--- a/Firmware/lcd.h
+++ b/Firmware/lcd.h
@@ -168,14 +168,6 @@ private:
 //! @retval 1 button was clicked
 #define LCD_CLICKED (lcd_click_trigger)
 
-// Setup Rotary Encoder Bit Values (for two pin encoders to indicate movement)
-// These values are independent of which pins are used for EN_A and EN_B indications
-// The rotary encoder part is also independent to the chipset used for the LCD
-#define encrot0 0
-#define encrot1 2
-#define encrot2 3
-#define encrot3 1
-
 ////////////////////////////////////
 
 //Custom characters defined in the first 8 characters of the LCD