1 files changed, 133 insertions, 0 deletions
diff --git a/code/src/main.c b/code/src/main.c
new file mode 100644
index 0000000..de2d35f
--- /dev/null
+++ b/code/src/main.c
@@ -0,0 +1,133 @@
+/*
+ Copyright 2021, tslil clingman
+
+ This program is free software: you can redistribute it and/or modify it under
+ the terms of the GNU General Public License as published by the Free Software
+ Foundation, either version 3 of the License.
+
+ This program is distributed in the hope that it will be useful, but WITHOUT ANY
+ WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+ PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License along with
+ this program. If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include <stdint.h>
+#include <avr/pgmspace.h>
+#include <util/delay.h>
+
+#include "TinyI2CMaster.h"
+
+#include "font.h"
+
+#define DISP1_ADDR 0x3C
+#define DISP2_ADDR 0x3D
+#define RTC_ADDR 0x68
+
+// -----------------------------------------------------------------------------
+// SSD1306 driver
+
+#define INIT_LEN 7
+PROGMEM const uint8_t init[INIT_LEN] = {0xAE, // display off
+                                        0x8D, // charge pump
+                                        0x14,
+                                        0xAF, // display on
+                                        0x20,
+                                        0xA6, // Normal display
+                                        0x02 // page address mode
+};
+
+void disp_init(const uint8_t addr, const uint8_t upside_down) {
+  i2c_start(addr,0);
+  i2c_write(0x00);
+  for (uint8_t k = 0; k<INIT_LEN; k++)
+    i2c_write(pgm_read_byte(&init[k]));
+  if (upside_down) {
+    i2c_write(0xA1);
+    i2c_write(0xC8);
+  }
+  i2c_stop();
+}
+
+void disp_draw_digit(const uint8_t addr, const uint8_t d, const uint8_t off) {
+  for (uint8_t y=0; y<8; y++, i2c_stop()) {
+    // Set cursor
+    i2c_start(addr,0);
+    i2c_write(0x00);
+    // Page select
+    i2c_write(0xB0|y); // 0<y<8 anyway
+    // Column select specialised to halves of screen
+    i2c_write(0); // 0..15, lower bits
+    i2c_write(0x10|off); // 0x10 .. 0x14, upper bits
+    // Prepare to draw
+    i2c_start(addr,0);
+    i2c_write(0x40);
+    for (uint8_t x=0; x<4; x++) {
+      // Read the byte
+      uint8_t b = pgm_read_byte(&font[d*32+(y*4+x)]);
+      // Unpack and draw it
+      for (uint8_t j=0; j<4; j++, b>>=2)
+        for (uint8_t l=0; l<4; l++)
+          i2c_write(((b&1)?0xF0:0x00)|
+                    ((b&2)?0x0F:0x00));
+    }
+  }
+}
+
+// -----------------------------------------------------------------------------
+// Interface
+
+uint8_t bcd_to_dec(uint8_t k) { return (((k)/16)*10) + ((k)%16); }
+
+uint8_t dec_to_bcd(uint8_t k) { return (((k)/10)*16) + ((k)%10); }
+
+int main(void) {
+  // Init screens
+  i2c_init();
+  disp_init(DISP1_ADDR,1);
+  disp_init(DISP2_ADDR,0);
+  // Setup input pullups
+  DDRA = ~(_BV(DDA0) | _BV(DDA1));
+  PORTA = _BV(DDA0) | _BV(DDA1);
+  // Tracking state
+  uint8_t input = 0, hours = 99, minutes = 99;
+  while(1) {
+    // Increase hours?
+    if (!(PINA&_BV(DDA0))) {
+        if ((hours+=1)>23) hours=0;
+        input = 1;
+    }
+    // Increase minutes?
+    if (!(PINA&_BV(DDA1))) {
+      if ((minutes+=1)>59) minutes=0;
+      input = 1;
+    }
+    // Store changes
+    if (input) {
+      input = 0;
+      i2c_start(RTC_ADDR,0);
+      i2c_write(0);
+      i2c_write(0); // Seconds
+      i2c_write(dec_to_bcd(minutes));
+      i2c_write(dec_to_bcd(hours));
+      i2c_stop();
+    }
+    // Draw minutes
+    disp_draw_digit(DISP1_ADDR, (minutes/10)%10, 0);
+    disp_draw_digit(DISP1_ADDR, (minutes%10), 4);
+    // Draw hours
+    disp_draw_digit(DISP2_ADDR, (hours/10)%10, 0);
+    disp_draw_digit(DISP2_ADDR, (hours%10), 4);
+    // Poll for update
+    i2c_start(RTC_ADDR,0);
+    i2c_write(1);
+    i2c_start(RTC_ADDR,2);
+    minutes = bcd_to_dec(i2c_read());
+    hours = bcd_to_dec(i2c_read());
+    i2c_stop();
+    // Delay
+    _delay_ms(100);
+  }
+  return 0;
+}