Interact with the display

Enable the SPI bus to configure the display and program its ram. For
that the fastest available SPI clock is used. To configure the display
a minimal config is used which is not identical but similar to the
displays datasheet. The display can only be filled columnwise so far.

firmware/src/Makefile

@@ -24,7 +24,7 @@ $(BIN): $(OBJ)
 	$(CC) $(CFLAGS) $< -o $@
 
 %.o: %.c
-	$(CC) $(CFLAGS) -Os -c $< -o $@
+	$(CC) $(CFLAGS) -c $< -o $@
 
 .PHONY: flash clean check size
 

firmware/src/main.c

@@ -4,6 +4,67 @@
 #include <util/delay.h>
 #include <stdbool.h>
 
+#define SPI_PORT PORTB
+#define SPI_DDR DDRB
+#define SPI_SCK PB5
+#define SPI_MOSI PB3
+#define SPI_SS PB2
+
+#define LCD_CD PB6
+#define LCD_RST PB1
+
+void spi_init(void) {
+    SPI_DDR |= (1 << SPI_SCK) | (1 << SPI_MOSI) | (1 << SPI_SS);
+    SPI_PORT |= (1 << SPI_SS);
+    SPCR = (1 << SPE) | (1 << MSTR);
+    SPSR = (1 << SPI2X);
+}
+
+uint8_t spi_byte(uint8_t data) {
+   SPDR = data;
+   while(!(SPSR & (1 << SPIF)));
+   return SPDR;
+ }
+
+void lcd_write(uint8_t data) {
+    SPI_PORT &= ~(1 << SPI_SS);
+    spi_byte(data);
+    SPI_PORT |= (1 << SPI_SS);
+}
+
+void lcd_init(void) {
+    SPI_DDR |= (1 << LCD_CD) | (1 << LCD_RST);
+    _delay_ms(1);
+    SPI_PORT |= (1 << LCD_RST);
+    _delay_ms(5);
+
+    lcd_write(0x40); // (6)  Set Scroll Line: Display start line 0
+    lcd_write(0xA1); // (13) Set SEG direction: SEG reverse
+    lcd_write(0xC0); // (14) Set COM direction: Normal COM0 - COM63
+    lcd_write(0xA6); // (11) Set Inverse Display: Display inverse off
+    lcd_write(0xA2); // (17) Set LCD Bias Ratio: Set Bias 1/9 (Duty 1/65)
+    lcd_write(0x2F); // (5)  Set Power Control: Booster, Regulator and Follower on
+    lcd_write(0x27); // (8)  Set VLCD Resistor Ratio: Set Contrast
+    lcd_write(0x81); // (9)  Set Electronic Volume: Set Contrast
+    lcd_write(0x10); // (9)  Set Electronic Volume: Set Contrast
+    lcd_write(0xAF); // (12) Set Display Enable: Display on
+}
+
+void lcd_fill(uint8_t data) {
+    for (uint8_t i = 0; i < 8; i++) {
+        SPI_PORT &= ~(1 << LCD_CD);
+        lcd_write(0x00);
+        lcd_write(0x10);
+        lcd_write(0xB0 + i); // page address 0 + i
+
+        SPI_PORT |= (1 << LCD_CD);
+
+        for (uint8_t j = 0; j < 102; j++) {
+            lcd_write(data);
+        }
+    }
+}
+
 int main(void) {
     // FastPWM: 1.25kHz
     TCCR0A = (1 << WGM01) | (1 << WGM00) | (1 << COM0B1);
@@ -14,6 +75,10 @@ int main(void) {
 
     bool reverse = 0;
 
+    spi_init();
+    lcd_init();
+    lcd_fill(0xFF);
+
     while (1) {
         _delay_ms(1);