Proper debouncing and dechattering

Move debouncing and dechattering to the beginning of the interrupt
service routines to handle them properly.

firmware/src/main.c

@@ -2,6 +2,7 @@
 #include <avr/io.h>
 #include <avr/interrupt.h>
 #include <util/delay.h>
+#include <util/twi.h>
 #include <assert.h>
 #include <stdbool.h>
 
@@ -17,6 +18,12 @@
 #define ENC_A (PINB & (1 << PB6))
 #define ENC_B (PINB & (1 << PB7))
 
+#define TWI_PORT PORTC
+#define TWI_SDA PC4
+#define TWI_SCL PC5
+
+#define SI5351_ADDRESS (0x60 << 1)
+
 #define SYM_ENTRY(SYM) { SYM, sizeof(SYM) / 2 }
 
 static uint8_t EEMEM eeprom_contrast = 8;
@@ -88,6 +95,9 @@ static const __flash uint8_t sym_t[] = { 0x0C, 0x0C, 0xFC, 0xFC, 0x0C, 0x0C,
 static const __flash uint8_t sym_u[] = { 0xFC, 0xFC, 0x00, 0x00, 0xFC, 0xFC,
                                          0x3F, 0x3F, 0x30, 0x30, 0x3F, 0x3F };
 
+static const __flash uint8_t sym_underscore[] = { 0x00, 0x00, 0x00, 0x00, 0x00,
+                                                  0x20, 0x20, 0x20, 0x20, 0x20 };
+
 static const __flash uint8_t sym_invalid[] = { 0x80, 0xE0, 0x98, 0xCC, 0x4C, 0x18, 0xE0, 0x80,
                                                0x01, 0x07, 0x1F, 0x24, 0x25, 0x1F, 0x07, 0x01};
 
@@ -133,7 +143,18 @@ static const struct symbol symbol_table[] = { SYM_ENTRY(sym_0),
                                               SYM_ENTRY(sym_r),
                                               SYM_ENTRY(sym_s),
                                               SYM_ENTRY(sym_t),
-                                              SYM_ENTRY(sym_u) };
+                                              SYM_ENTRY(sym_u),
+                                              SYM_ENTRY(sym_invalid),
+                                              SYM_ENTRY(sym_invalid),
+                                              SYM_ENTRY(sym_invalid),
+                                              SYM_ENTRY(sym_invalid),
+                                              SYM_ENTRY(sym_invalid),
+                                              SYM_ENTRY(sym_invalid),
+                                              SYM_ENTRY(sym_invalid),
+                                              SYM_ENTRY(sym_invalid),
+                                              SYM_ENTRY(sym_invalid),
+                                              SYM_ENTRY(sym_underscore),
+};
 
 enum input { cw, ccw, click, hold };
 
@@ -166,6 +187,7 @@ static void lcd_write(const uint8_t data) {
 }
 
 static void lcd_init(void) {
+    // TODO: Optimize waiting times
     SPI_DDR |= (1 << LCD_CD) | (1 << LCD_RST);
     _delay_ms(1);
     SPI_PORT |= (1 << LCD_RST);
@@ -200,12 +222,12 @@ static void lcd_update_backlight(void) {
     case 3:
     case 4:
     case 5:
-        TCCR0B = 0x0C; // prescaler = 256;
+        TCCR0B = 0x0C; // Prescaler = 256;
         DDRD |= (1 << PD5);
         OCR0B = value_backlight - 1;
         break;
     default:
-        TCCR0B = 0x0B; // prescaler = 64;
+        TCCR0B = 0x0B; // Prescaler = 64;
         DDRD |= (1 << PD5);
         OCR0B = value_backlight - 4;
         break;
@@ -280,6 +302,7 @@ static void lcd_write_integer_page(const uint8_t integer,
         uint16_t comperator = 1;
 
         for (; comperator <= integer; comperator *= 10, input_digits++);
+
         for (int8_t i = digits - input_digits; i > 0; i--) {
             lcd_write_kerning(2, invert);
             lcd_write_digit_page(0, page, invert);
@@ -312,7 +335,98 @@ static void lcd_splash(void) {
     }
 }
 
-static void lcd_home(void) {
+static void twi_error(void) {
+    lcd_fill(0xFF);
+
+    for (uint8_t i = 0; i < 2; i++) {
+        lcd_move_cursor(0, i);
+        lcd_write_string_page("TW_STATUS:\0", i, true);
+        lcd_write_kerning(2, true);
+        lcd_write_integer_page(TW_STATUS, 3, i, true);
+    }
+
+    for (uint8_t i = 0; i < 2; i++) {
+        lcd_move_cursor(0, i + 2);
+        lcd_write_string_page("TW_DATA:\0", i, true);
+        lcd_write_kerning(16, true);
+        lcd_write_integer_page(TWDR, 3, i, true);
+    }
+
+    for (;;);
+}
+
+static void twi_start(void) {
+    TWCR = (1 << TWINT) | (1 << TWSTA) | (1 << TWEN); // Start transmission
+    while (!(TWCR & (1 << TWINT))); // Wait until start is transmitted
+
+    if (TW_STATUS != TW_START) // Check status
+        twi_error();
+}
+
+static uint8_t twi_transmit(const uint8_t data) {
+    TWDR = data;
+    TWCR = (1 << TWINT) | (1 << TWEN); // Transmit data
+    while (!(TWCR & (1 << TWINT))); // Wait until data is transmitted
+
+    return TW_STATUS;
+}
+
+static uint8_t twi_receive(void) {
+    TWCR = (1 << TWINT) | (1 << TWEN); // Receive data
+    while (!(TWCR & (1 << TWINT))); // Wait until data is received
+
+    return TW_STATUS;
+}
+
+static void twi_stop(void) {
+    TWCR = (1 << TWINT) | (1 << TWSTO) | (1 << TWEN);
+}
+
+static uint8_t twi_read_register(const uint8_t address,
+                                 const uint8_t reg) {
+    twi_start();
+
+    if (twi_transmit(address) != TW_MT_SLA_ACK)
+        twi_error();
+
+    if (twi_transmit(reg) != TW_MT_DATA_ACK)
+        twi_error();
+
+    twi_stop();
+
+    _delay_us(2);
+
+    twi_start();
+
+    if (twi_transmit(address + 1) != TW_MR_SLA_ACK)
+        twi_error();
+
+    if (twi_receive() != TW_MR_DATA_NACK)
+        twi_error();
+
+    twi_stop();
+
+    return TWDR;
+}
+
+static void twi_write_register(const uint8_t address,
+                               const uint8_t reg,
+                               const uint8_t data) {
+    twi_start();
+
+    if (twi_transmit(address) != TW_MT_SLA_ACK)
+        twi_error();
+
+    if (twi_transmit(reg) != TW_MT_DATA_ACK)
+        twi_error();
+
+    if (twi_transmit(data) != TW_MT_DATA_ACK)
+        twi_error();
+
+    twi_stop();
+}
+
+static void draw_home(void) {
     lcd_fill(0x00);
 
     bool ch1_selected = false;
@@ -354,7 +468,7 @@ static void lcd_home(void) {
     }
 }
 
-static void lcd_setup(void) {
+static void draw_setup(void) {
     lcd_fill(0x00);
 
     bool contrast_selected = false;
@@ -393,7 +507,8 @@ static void lcd_setup(void) {
         lcd_write_string_page("CONTRAST:\0", i, contrast_selected);
         lcd_write_kerning(2, contrast_selected);
         lcd_write_kerning(16, false);
-        lcd_write_integer_page(value_contrast, 2, i, change_contrast_selected);
+        lcd_write_integer_page(value_contrast, 2, i,
+                               change_contrast_selected);
         lcd_write_kerning(2, change_contrast_selected);
     }
 
@@ -402,7 +517,8 @@ static void lcd_setup(void) {
         lcd_write_string_page("BACKLIGHT:\0", i, backlight_selected);
         lcd_write_kerning(2, backlight_selected);
         lcd_write_kerning(5, false);
-        lcd_write_integer_page(value_backlight, 3, i, change_backlight_selected);
+        lcd_write_integer_page(value_backlight, 3, i,
+                               change_backlight_selected);
         lcd_write_kerning(2, change_backlight_selected);
     }
 
@@ -416,7 +532,7 @@ static void lcd_setup(void) {
 static void change_state(const enum state new_state) {
     switch (new_state) {
     case home:
-        lcd_home();
+        draw_home();
         current_state = home;
         break;
     case ch1:
@@ -427,7 +543,7 @@ static void change_state(const enum state new_state) {
         break;
     case setup:
         setup_state = contrast;
-        lcd_setup();
+        draw_setup();
         current_state = setup;
         break;
     }
@@ -439,13 +555,13 @@ static void update_home(const enum input event) {
         home_state++;
         if (home_state > setup)
             home_state = ch1;
-        lcd_home();
+        draw_home();
         break;
     case ccw:
         home_state--;
         if (home_state > setup)
             home_state = setup;
-        lcd_home();
+        draw_home();
         break;
     case click:
         change_state(home_state);
@@ -479,7 +595,7 @@ static void update_setup(const enum input event) {
             }
             break;
         }
-        lcd_setup();
+        draw_setup();
         break;
     case ccw:
         switch (setup_state) {
@@ -503,17 +619,17 @@ static void update_setup(const enum input event) {
             }
             break;
         }
-        lcd_setup();
+        draw_setup();
         break;
     case click:
         switch (setup_state) {
         case contrast:
             setup_state = change_contrast;
-            lcd_setup();
+            draw_setup();
             break;
         case backlight:
             setup_state = change_backlight;
-            lcd_setup();
+            draw_setup();
             break;
         case back:
             change_state(home);
@@ -521,12 +637,12 @@ static void update_setup(const enum input event) {
         case change_contrast:
             eeprom_update_byte(&eeprom_contrast, value_contrast);
             setup_state = contrast;
-            lcd_setup();
+            draw_setup();
             break;
         case change_backlight:
             eeprom_update_byte(&eeprom_backlight, value_backlight);
             setup_state = backlight;
-            lcd_setup();
+            draw_setup();
             break;
         }
         break;
@@ -541,13 +657,13 @@ static void update_setup(const enum input event) {
             setup_state = contrast;
             value_contrast = eeprom_read_byte(&eeprom_contrast);
             lcd_update_contrast();
-            lcd_setup();
+            draw_setup();
             break;
         case change_backlight:
             setup_state = backlight;
             value_backlight = eeprom_read_byte(&eeprom_backlight);
             lcd_update_backlight();
-            lcd_setup();
+            draw_setup();
             break;
         }
         break;
@@ -575,6 +691,9 @@ static void update_state(const enum input event) {
 ISR(PCINT0_vect) {
     cli();
 
+    // Dechatter
+    _delay_ms(3);
+
     switch (enc) {
     case 0:
         if (ENC_A && !ENC_B)
@@ -608,16 +727,16 @@ ISR(PCINT0_vect) {
         break;
     }
 
-    // TODO: proper dechattering
-    _delay_ms(3);
-
     sei();
 }
 
-// encoder button interrupt
+// Encoder button interrupt
 ISR(PCINT1_vect) {
     cli();
 
+    // Debounce
+    _delay_ms(2);
+
     if (PINC & (1 << PC0)) { // Release
         if (TCCR1B & (1 << CS10)) // If release before hold
             update_state(click); // Switch to selected state
@@ -629,9 +748,6 @@ ISR(PCINT1_vect) {
             TCCR1B |= (1 << CS11) | (1 << CS10); // Enable Timer/Counter1
     }
 
-    // TODO: Proper debouncing
-    _delay_ms(3);
-
     sei();
 }
 
@@ -650,13 +766,12 @@ int main(void) {
     value_contrast = eeprom_read_byte(&eeprom_contrast);
     value_backlight = eeprom_read_byte(&eeprom_backlight);
 
-    // Init backlight: FastPWM: 1.25kHz
+    // Init backlight
-    // TODO: Try to get the backlit even more dim
     TCCR0A |= (1 << WGM01) | (1 << WGM00) | (1 << COM0B1);
     OCR0A = 255;
     lcd_update_backlight();
 
-    // SPI setup
+    // SPI and LCD init
     spi_init();
     lcd_init();
 
@@ -674,11 +789,19 @@ int main(void) {
     OCR1A = 65535;
     TIMSK1 |= (1 << OCIE1A); // Enable match compare A
 
-    // Show splash screen and load the menu
+    // Show splash screen
     lcd_splash();
     _delay_ms(2000);
+
+    // Load the menu
     change_state(current_state);
 
+    // Set TWI bit rate to 200kHz
+    TWBR = 12;
+
+    (void) &twi_read_register;
+    (void) &twi_write_register;
+
     // Enable interrupts
     sei();