Draw float to screen

1 files changed, 193 insertions, 0 deletions

diff --git a/src/display.c b/src/display.c
new file mode 100644
index 0000000..6cb0f1c
--- /dev/null
+++ b/src/display.c
@@ -0,0 +1,193 @@
+#include <avr/io.h>
+#include <avr/pgmspace.h>
+#include <util/delay.h>
+
+#include "display.h"
+#include "font.h"
+
+uint8_t cursor_y = 0;
+uint8_t cursor_x = 0;
+
+static uint8_t i2c_transfer(uint8_t usisr_val) {
+  USISR = usisr_val;
+  // 2-wire i2c + (USICS1+USICLK = timer0 clock) + 3-wire master
+  uint8_t cr = (1 << USIWM1) | (1 << USICS1) | (1 << USICLK) | (1 << USITC);
+  do {
+    _delay_us(I2C_DELAY_US);
+    USICR = cr;
+    while (!(PINA & (1 << DISPLAY_SCL)))
+      ; // Wait for next clock falling edge
+    _delay_us(I2C_DELAY_US);
+    USICR = cr;
+  } while (!(USISR & (1 << USIOIF)));
+  _delay_us(I2C_DELAY_US);
+
+  uint8_t data = USIDR;
+  USIDR = 0xFF;
+  DDRA |= (1 << DISPLAY_SDA);
+  return data;
+}
+
+static void i2c_init(void) {
+  PORTA |= (1 << DISPLAY_SDA) | (1 << DISPLAY_SCL);
+  DDRA |= (1 << DISPLAY_SDA) | (1 << DISPLAY_SCL);
+  USIDR = 0xFF;
+  // 2-wire i2c + (USICS1+USICLK = timer0 clock)
+  USICR = (1 << USIWM1) | (1 << USICS1) | (1 << USICLK);
+  // Start interrupt + overflow interrupt + stop interrupt + output collision
+  USISR = (1 << USISIF) | (1 << USIOIF) | (1 << USIPF) | (1 << USIDC);
+}
+
+void i2c_start(void) {
+  PORTA |= (1 << DISPLAY_SCL);
+  while (!(PINA & (1 << DISPLAY_SCL)))
+    ; // Wait for next clock falling edge
+  _delay_us(I2C_DELAY_US);
+  PORTA &= ~(1 << DISPLAY_SDA); // SDA low while SCL high = START
+  _delay_us(I2C_DELAY_US);
+  PORTA &= ~(1 << DISPLAY_SCL);
+  PORTA |= (1 << DISPLAY_SDA);
+}
+
+void i2c_stop(void) {
+  PORTA &= ~(1 << DISPLAY_SDA);
+  _delay_us(I2C_DELAY_US);
+  PORTA |= (1 << DISPLAY_SCL);
+  while (!(PINA & (1 << DISPLAY_SCL)))
+    ;
+  _delay_us(I2C_DELAY_US);
+  PORTA |= (1 << DISPLAY_SDA); // SDA high while SCL high = STOP
+  _delay_us(I2C_DELAY_US);
+}
+
+void i2c_write(uint8_t data) {
+  PORTA &= ~(1 << DISPLAY_SCL);
+  USIDR = data;
+  // transfer 8 bits: counter=0 overflows after 16 edges (8 clocks)
+  i2c_transfer((1 << USISIF) | (1 << USIOIF) | (1 << USIPF) | (1 << USIDC) |
+               0x00);
+  DDRA &= ~(1 << DISPLAY_SDA);
+  // transfer 1 bit: counter=0x0E overflows after 2 edges (1 clock)
+  i2c_transfer((1 << USISIF) | (1 << USIOIF) | (1 << USIPF) | (1 << USIDC) |
+               0x0E);
+}
+
+void display_cmd(uint8_t cmd) {
+  i2c_start();
+  i2c_write(OLED_ADDR);
+  i2c_write(0x00); // Control byte: Co=0, D/C#=0
+  i2c_write(cmd);
+  i2c_stop();
+}
+
+void display_clear(void) {
+  for (uint8_t page = 0; page < 8; page++) {
+    display_cmd(DCMD_SET_PAGE_START | page);
+    display_cmd(0x00);
+    display_cmd(DCMD_SET_START_ADDR_HIGHER_COL);
+    i2c_start();
+    i2c_write(OLED_ADDR);
+    i2c_write(0x40);
+    for (uint8_t col = 0; col < 128; col++)
+      i2c_write(0x00);
+    i2c_stop();
+  }
+}
+
+void display_init(void) {
+  i2c_init();
+  _delay_ms(40);
+
+  display_cmd(DCMD_DISPLAY_OFF);
+  display_cmd(DCMD_SET_CLOCK_DIV);
+  display_cmd(0x80);
+  display_cmd(DCMD_SET_MUX_RATIO);
+  display_cmd(63); // 64 rows
+  display_cmd(DCMD_SET_OFFSET);
+  display_cmd(0x00);
+  display_cmd(DCMD_SET_START_LINE);
+  display_cmd(DCMD_SET_CHARGE_PUMP);
+  display_cmd(DCMD_CHARGE_PUMP_ENABLE);
+  display_cmd(DCMD_SET_ADDRESSING_MODE);
+  display_cmd(DCMD_ADDR_HORIZONTAL);
+  display_cmd(DCMD_SET_SEGMENT_REMAP);
+  display_cmd(DCMD_SET_COM_SCAN_DIRECTION);
+  display_cmd(DCMD_SET_COM_PINS);
+  display_cmd(0x12);
+  display_cmd(DCMD_SET_CONTRAST);
+  display_cmd(207);
+  display_cmd(DCMD_SET_PRECHARGE_PERIOD);
+  display_cmd(0xF1);
+  display_cmd(DCMD_SET_VCOMH_DESELECT);
+  display_cmd(0x40);
+  display_cmd(DCMD_OUTPUT_FOLLOWS_RAM);
+  display_cmd(DCMD_NORMAL_MODE);
+  display_cmd(DCMD_DISPLAY_ON);
+
+  display_clear();
+}
+
+static uint8_t scale_column(uint8_t font_byte, uint8_t page) {
+  uint8_t out = 0;
+  for (uint8_t b = 0; b < 8; b++) {
+    uint8_t src = (page * 8 + b) / FONT_SCALE_Y;
+    if (src < FONT_GLYPH_HEIGHT && (font_byte & (1 << src)))
+      out |= (1 << b);
+  }
+  return out;
+}
+
+void display_draw_char(uint8_t c) {
+  if (c < FONT_GLYPH_FIRST_CHAR || c > FONT_GLYPH_LAST_CHAR)
+    return;
+  uint16_t offset = (uint16_t)(c - FONT_GLYPH_FIRST_CHAR) * FONT_GLYPH_WIDTH;
+
+  uint8_t pages = (FONT_GLYPH_HEIGHT * FONT_SCALE_Y + 7) / 8;
+  for (uint8_t p = 0; p < pages; p++) {
+    display_cmd(DCMD_SET_PAGE_START | ((cursor_y + p) & 0x07));
+    display_cmd(cursor_x & 0x0F);
+    display_cmd(DCMD_SET_START_ADDR_HIGHER_COL | (cursor_x >> 4));
+
+    i2c_start();
+    i2c_write(OLED_ADDR);
+    i2c_write(0x40);
+    for (uint8_t col = 0; col < FONT_GLYPH_WIDTH; col++) {
+      uint8_t glyph = pgm_read_byte(&FONT_BITMAP[offset + col]);
+      uint8_t scaled = scale_column(glyph, p);
+      for (uint8_t r = 0; r < FONT_SCALE_X; r++)
+        i2c_write(scaled);
+    }
+    for (uint8_t r = 0; r < FONT_SCALE_X; r++)
+      i2c_write(0x00);
+    i2c_stop();
+  }
+
+  cursor_x += (FONT_GLYPH_WIDTH + CHAR_SPACING) * FONT_SCALE_X;
+}
+
+void display_draw_float2(float num) {
+  cursor_x = 5;
+  cursor_y = 2;
+
+  if (num < 0) {
+    display_draw_char('-');
+    num = -num;
+  }
+
+  int val = (int)(num * 10); // include 1 decimal place
+  int digit;
+  uint8_t is_first = 1;
+
+  for (uint16_t i = 1000; i >= 1; i /= 10, is_first = 0) {
+    // 2 digits left means tis decimal time
+    if (i == 1)
+      display_draw_char('.');
+    digit = (val / i) % 10;
+    val %= i;
+    // if first digit is 0, draw space (tis garbage code)
+    if (is_first && digit == 0)
+      display_draw_char(' ');
+    else
+      display_draw_char(digit + '0');
+  }
+}