initial commit

.gitmodules

@@ -0,0 +1,6 @@
+[submodule "code/avr-ds3231"]
+	path = code/avr-ds3231
+	url = https://github.com/ecnx/avr-ds3231.git
+[submodule "code/avr-i2c"]
+	path = code/avr-i2c
+	url = https://github.com/ecnx/avr-i2c.git

code/.clangd

@@ -0,0 +1,10 @@
+CompileFlags:
+  Compiler: avr-gcc
+  Add: [
+    -mmcu=atmega48,
+    -I/usr/avr/include,
+    -Iavr-i2c,
+    -Iavr-ds3231,
+    -Wall,
+    -Wextra,
+  ]

code/Makefile

@@ -0,0 +1,6 @@
+compile:
+	avr-gcc -DF_CPU=8000000 -Iavr-i2c -Iavr-ds3231 -Os -flto -mmcu=atmega48 main.c avr-ds3231/ds3231.c avr-i2c/i2c.c -o nixie
+	avr-size -A nixie
+
+flash:
+	avrdude -p m48 -c usbasp -P usb -B4 -U flash:w:nixie

code/avr-ds3231

@@ -0,0 +1 @@
+Subproject commit 8606f788c818af62633931564b64dbeb077357ee

code/avr-i2c

@@ -0,0 +1 @@
+Subproject commit 474767e1c0ed2cd1d8e30828b769143c9a5547bb

code/main.c

@@ -0,0 +1,253 @@
+#include <avr/interrupt.h>
+#include <avr/io.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <util/delay.h>
+
+#include <ds3231.h>
+
+#ifndef bit
+#define bit(b) (1 << b)
+#endif
+
+/**
+ * high nibble: BCD output digit
+ * low nibble: button inputs, leftmost button is least significant bit
+ */
+#define BCD_BTN_PORT PORTD
+#define BTN_PIN PIND
+#define BCD_BTN_DDR DDRD
+
+/**
+ * low nibble: nixie anode power
+ * one bit per digit, leftmost nixie is least significant bit
+ */
+#define NIXIE_PORT PORTC
+#define NIXIE_DDR DDRC
+
+/**
+ * other control pins
+ * - bit 0: K155ID1 power (active high)
+ * - bit 1: HV shutdown (active high; not connected)
+ * - bit 2: dots anode power
+ */
+#define ETC_PORT PORTB
+#define ETC_DDR DDRB
+
+#define ETC_ID1 bit(0)
+#define ETC_HVSD bit(1)
+#define ETC_DOTS bit(2)
+
+#define READ_RTC_INTERVAL_MS 71
+#define BTN_DEBOUNCE_MS 50
+
+// runtime variables
+volatile uint32_t msec = 0;
+
+struct ds3231_clock_t clock = {0};
+bool flag_read_rtc = true;
+
+bool set_mode_active = false;
+uint8_t set_mode_idx = 0;
+uint8_t set_mode_digits[4] = {0};
+
+uint32_t button_inhibit_ms[4] = {0};
+bool flag_button_pressed[4] = {false};
+
+bool is_button_pressed(uint8_t id) {
+  return (BTN_PIN & bit(id)) == 0;
+}
+
+void handle_button_press(uint8_t id) {
+  switch (id) {
+    // toggle set mode; set new time
+    case 0: {
+      if (set_mode_active) {
+        clock.hours = set_mode_digits[0] * 10 + set_mode_digits[1];
+        clock.minutes = set_mode_digits[2] * 10 + set_mode_digits[3];
+        clock.seconds = 0;
+        ds3231_write_clock(&clock);
+
+        set_mode_active = false;
+      } else {
+        ds3231_read_clock(&clock);
+        set_mode_digits[0] = clock.hours / 10;
+        set_mode_digits[1] = clock.hours % 10;
+        set_mode_digits[2] = clock.minutes / 10;
+        set_mode_digits[3] = clock.minutes % 10;
+
+        set_mode_active = true;
+      }
+
+      break;
+    }
+
+    // move between digits
+    case 1: {
+      if (set_mode_active) {
+        set_mode_idx = (set_mode_idx + 1) % 4;
+      }
+
+      break;
+    }
+
+    // up
+    case 2: {
+      if (set_mode_active) {
+        set_mode_digits[set_mode_idx]++;
+
+        if (set_mode_idx == 0) {
+          set_mode_digits[set_mode_idx] %= 3;
+        } else if (set_mode_idx == 1 && set_mode_digits[0] == 2) {
+          set_mode_digits[set_mode_idx] %= 4;
+        } else if (set_mode_idx == 2) {
+          set_mode_digits[set_mode_idx] %= 6;
+        } else {
+          set_mode_digits[set_mode_idx] %= 10;
+        }
+      }
+
+      break;
+    }
+
+    // down
+    case 3: {
+      if (set_mode_active) {
+        set_mode_digits[set_mode_idx]--;
+
+        if (set_mode_idx == 0) {
+          set_mode_digits[set_mode_idx] += 3;
+          set_mode_digits[set_mode_idx] %= 3;
+        } else if (set_mode_idx == 1 && set_mode_digits[0] == 2) {
+          set_mode_digits[set_mode_idx] += 4;
+          set_mode_digits[set_mode_idx] %= 4;
+        } else if (set_mode_idx == 2) {
+          set_mode_digits[set_mode_idx] += 6;
+          set_mode_digits[set_mode_idx] %= 6;
+        } else {
+          set_mode_digits[set_mode_idx] += 10;
+          set_mode_digits[set_mode_idx] %= 10;
+        }
+      }
+
+      break;
+    }
+  }
+}
+
+/**
+ * sets up timer0 for 1ms interrupts
+ */
+void timer_setup() {
+  // Set the compare value to 249 to make the timer trigger once every 250 clock cycles.
+  TCCR0A = bit(WGM01);
+  OCR0A = 124;
+
+  // Enable the timer and interrupts
+  TIMSK0 |= bit(OCIE0A);
+  sei();
+
+  // Set clock prescaler for timer0 to 1/64 (= 250kHz)
+  // This also starts the timer
+  TCCR0B |= 0b00000011;
+  // TCCR0B |= 0b00000101;
+}
+
+bool error = false;
+
+int main() {
+  BCD_BTN_DDR = 0xf0;  // set BCD pins as output
+  BCD_BTN_PORT = 0x0f; // enable input pull-ups
+
+  NIXIE_DDR = 0x0f;
+
+  ETC_DDR = 0x07;
+  ETC_PORT |= ETC_ID1; // enable power to K155ID1
+
+  timer_setup();
+
+  // button interrupts
+  PCMSK2 |= 0x0f; // enable pin change interrupts on button pins
+  PCICR |= bit(PCIE2);
+
+  for (;;) {
+    if (flag_read_rtc) {
+      flag_read_rtc = false;
+
+      if (ds3231_read_clock(&clock) != 0) {
+        error = true;
+      }
+
+      if (clock.seconds % 2 == 0) {
+        ETC_PORT &= ~ETC_DOTS;
+      } else {
+        ETC_PORT |= ETC_DOTS;
+      }
+    }
+
+    for (int i = 0; i < 4; i++) {
+      if (flag_button_pressed[i]) {
+        flag_button_pressed[i] = false;
+        handle_button_press(i);
+      }
+    }
+  }
+}
+
+void clear_digits() {
+  NIXIE_PORT = 0;
+  BCD_BTN_PORT &= ~(0xf0);
+}
+
+void show_digit(uint8_t digit, uint8_t nixie_idx) {
+  BCD_BTN_PORT &= ~(0xf0);
+  BCD_BTN_PORT |= digit << 4;
+  NIXIE_PORT = bit(nixie_idx);
+}
+
+// millisecond counter
+ISR(TIMER0_COMPA_vect) {
+  // time
+  msec++;
+  if (msec % READ_RTC_INTERVAL_MS == 0) {
+    flag_read_rtc = true;
+  }
+
+  // dots
+  if (set_mode_active && msec % 250 == 0) {
+    ETC_PORT ^= ETC_DOTS;
+  }
+
+  // digits
+  uint8_t nixie_idx = msec % 4;
+  if (set_mode_active) {
+    if (nixie_idx == set_mode_idx || msec % 16 < 4) {
+      show_digit(set_mode_digits[nixie_idx], nixie_idx);
+    } else {
+      clear_digits();
+    }
+  } else {
+    uint32_t digit = nixie_idx == 0   ? clock.hours / 10
+                     : nixie_idx == 1 ? clock.hours % 10
+                     : nixie_idx == 2 ? clock.minutes / 10
+                                      : clock.minutes % 10;
+    show_digit(digit, nixie_idx);
+  }
+
+  // button debounce
+  for (int i = 0; i < 4; i++) {
+    if (button_inhibit_ms[i] > 0) {
+      button_inhibit_ms[i]--;
+    }
+  }
+}
+
+// button press detection
+ISR(PCINT2_vect) {
+  for (int i = 0; i < 4; i++) {
+    if (is_button_pressed(i) && button_inhibit_ms[i] == 0) {
+      flag_button_pressed[i] = true;
+      button_inhibit_ms[i] = BTN_DEBOUNCE_MS;
+    }
+  }
+}

kicad/.gitignore

@@ -0,0 +1 @@
+nixie-backups/*

kicad/nixie.kicad_pcb

@@ -0,0 +1,2 @@
+(kicad_pcb (version 20240108) (generator "pcbnew") (generator_version "8.0")
+)

kicad/nixie.kicad_prl

@@ -0,0 +1,83 @@
+{
+  "board": {
+    "active_layer": 0,
+    "active_layer_preset": "",
+    "auto_track_width": true,
+    "hidden_netclasses": [],
+    "hidden_nets": [],
+    "high_contrast_mode": 0,
+    "net_color_mode": 1,
+    "opacity": {
+      "images": 0.6,
+      "pads": 1.0,
+      "tracks": 1.0,
+      "vias": 1.0,
+      "zones": 0.6
+    },
+    "selection_filter": {
+      "dimensions": true,
+      "footprints": true,
+      "graphics": true,
+      "keepouts": true,
+      "lockedItems": false,
+      "otherItems": true,
+      "pads": true,
+      "text": true,
+      "tracks": true,
+      "vias": true,
+      "zones": true
+    },
+    "visible_items": [
+      0,
+      1,
+      2,
+      3,
+      4,
+      5,
+      8,
+      9,
+      10,
+      11,
+      12,
+      13,
+      15,
+      16,
+      17,
+      18,
+      19,
+      20,
+      21,
+      22,
+      23,
+      24,
+      25,
+      26,
+      27,
+      28,
+      29,
+      30,
+      32,
+      33,
+      34,
+      35,
+      36,
+      39,
+      40
+    ],
+    "visible_layers": "fffffff_ffffffff",
+    "zone_display_mode": 0
+  },
+  "git": {
+    "repo_password": "",
+    "repo_type": "",
+    "repo_username": "",
+    "ssh_key": ""
+  },
+  "meta": {
+    "filename": "nixie.kicad_prl",
+    "version": 3
+  },
+  "project": {
+    "files": []
+  }
+}

kicad/nixie.kicad_pro

@@ -0,0 +1,392 @@
+{
+  "board": {
+    "3dviewports": [],
+    "design_settings": {
+      "defaults": {},
+      "diff_pair_dimensions": [],
+      "drc_exclusions": [],
+      "rules": {},
+      "track_widths": [],
+      "via_dimensions": []
+    },
+    "ipc2581": {
+      "dist": "",
+      "distpn": "",
+      "internal_id": "",
+      "mfg": "",
+      "mpn": ""
+    },
+    "layer_presets": [],
+    "viewports": []
+  },
+  "boards": [],
+  "cvpcb": {
+    "equivalence_files": []
+  },
+  "erc": {
+    "erc_exclusions": [],
+    "meta": {
+      "version": 0
+    },
+    "pin_map": [
+      [
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        1,
+        0,
+        0,
+        0,
+        0,
+        2
+      ],
+      [
+        0,
+        2,
+        0,
+        1,
+        0,
+        0,
+        1,
+        0,
+        2,
+        2,
+        2,
+        2
+      ],
+      [
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        1,
+        0,
+        1,
+        0,
+        1,
+        2
+      ],
+      [
+        0,
+        1,
+        0,
+        0,
+        0,
+        0,
+        1,
+        1,
+        2,
+        1,
+        1,
+        2
+      ],
+      [
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        1,
+        0,
+        0,
+        0,
+        0,
+        2
+      ],
+      [
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        2
+      ],
+      [
+        1,
+        1,
+        1,
+        1,
+        1,
+        0,
+        1,
+        1,
+        1,
+        1,
+        1,
+        2
+      ],
+      [
+        0,
+        0,
+        0,
+        1,
+        0,
+        0,
+        1,
+        0,
+        0,
+        0,
+        0,
+        2
+      ],
+      [
+        0,
+        2,
+        1,
+        2,
+        0,
+        0,
+        1,
+        0,
+        2,
+        2,
+        2,
+        2
+      ],
+      [
+        0,
+        2,
+        0,
+        1,
+        0,
+        0,
+        1,
+        0,
+        2,
+        0,
+        0,
+        2
+      ],
+      [
+        0,
+        2,
+        1,
+        1,
+        0,
+        0,
+        1,
+        0,
+        2,
+        0,
+        0,
+        2
+      ],
+      [
+        2,
+        2,
+        2,
+        2,
+        2,
+        2,
+        2,
+        2,
+        2,
+        2,
+        2,
+        2
+      ]
+    ],
+    "rule_severities": {
+      "bus_definition_conflict": "error",
+      "bus_entry_needed": "error",
+      "bus_to_bus_conflict": "error",
+      "bus_to_net_conflict": "error",
+      "conflicting_netclasses": "error",
+      "different_unit_footprint": "error",
+      "different_unit_net": "error",
+      "duplicate_reference": "error",
+      "duplicate_sheet_names": "error",
+      "endpoint_off_grid": "warning",
+      "extra_units": "error",
+      "global_label_dangling": "warning",
+      "hier_label_mismatch": "error",
+      "label_dangling": "error",
+      "lib_symbol_issues": "warning",
+      "missing_bidi_pin": "warning",
+      "missing_input_pin": "warning",
+      "missing_power_pin": "error",
+      "missing_unit": "warning",
+      "multiple_net_names": "warning",
+      "net_not_bus_member": "warning",
+      "no_connect_connected": "warning",
+      "no_connect_dangling": "warning",
+      "pin_not_connected": "error",
+      "pin_not_driven": "error",
+      "pin_to_pin": "warning",
+      "power_pin_not_driven": "error",
+      "similar_labels": "warning",
+      "simulation_model_issue": "ignore",
+      "unannotated": "error",
+      "unit_value_mismatch": "error",
+      "unresolved_variable": "error",
+      "wire_dangling": "error"
+    }
+  },
+  "libraries": {
+    "pinned_footprint_libs": [],
+    "pinned_symbol_libs": []
+  },
+  "meta": {
+    "filename": "nixie.kicad_pro",
+    "version": 1
+  },
+  "net_settings": {
+    "classes": [
+      {
+        "bus_width": 12,
+        "clearance": 0.2,
+        "diff_pair_gap": 0.25,
+        "diff_pair_via_gap": 0.25,
+        "diff_pair_width": 0.2,
+        "line_style": 0,
+        "microvia_diameter": 0.3,
+        "microvia_drill": 0.1,
+        "name": "Default",
+        "pcb_color": "rgba(0, 0, 0, 0.000)",
+        "schematic_color": "rgba(0, 0, 0, 0.000)",
+        "track_width": 0.2,
+        "via_diameter": 0.6,
+        "via_drill": 0.3,
+        "wire_width": 6
+      }
+    ],
+    "meta": {
+      "version": 3
+    },
+    "net_colors": null,
+    "netclass_assignments": null,
+    "netclass_patterns": []
+  },
+  "pcbnew": {
+    "last_paths": {
+      "gencad": "",
+      "idf": "",
+      "netlist": "",
+      "plot": "",
+      "pos_files": "",
+      "specctra_dsn": "",
+      "step": "",
+      "svg": "",
+      "vrml": ""
+    },
+    "page_layout_descr_file": ""
+  },
+  "schematic": {
+    "annotate_start_num": 0,
+    "bom_export_filename": "",
+    "bom_fmt_presets": [],
+    "bom_fmt_settings": {
+      "field_delimiter": ",",
+      "keep_line_breaks": false,
+      "keep_tabs": false,
+      "name": "CSV",
+      "ref_delimiter": ",",
+      "ref_range_delimiter": "",
+      "string_delimiter": "\""
+    },
+    "bom_presets": [],
+    "bom_settings": {
+      "exclude_dnp": false,
+      "fields_ordered": [
+        {
+          "group_by": false,
+          "label": "Reference",
+          "name": "Reference",
+          "show": true
+        },
+        {
+          "group_by": true,
+          "label": "Value",
+          "name": "Value",
+          "show": true
+        },
+        {
+          "group_by": false,
+          "label": "Datasheet",
+          "name": "Datasheet",
+          "show": true
+        },
+        {
+          "group_by": false,
+          "label": "Footprint",
+          "name": "Footprint",
+          "show": true
+        },
+        {
+          "group_by": false,
+          "label": "Qty",
+          "name": "${QUANTITY}",
+          "show": true
+        },
+        {
+          "group_by": true,
+          "label": "DNP",
+          "name": "${DNP}",
+          "show": true
+        }
+      ],
+      "filter_string": "",
+      "group_symbols": true,
+      "name": "Grouped By Value",
+      "sort_asc": true,
+      "sort_field": "Reference"
+    },
+    "connection_grid_size": 50.0,
+    "drawing": {
+      "dashed_lines_dash_length_ratio": 12.0,
+      "dashed_lines_gap_length_ratio": 3.0,
+      "default_line_thickness": 6.0,
+      "default_text_size": 50.0,
+      "field_names": [],
+      "intersheets_ref_own_page": false,
+      "intersheets_ref_prefix": "",
+      "intersheets_ref_short": false,
+      "intersheets_ref_show": false,
+      "intersheets_ref_suffix": "",
+      "junction_size_choice": 3,
+      "label_size_ratio": 0.375,
+      "operating_point_overlay_i_precision": 3,
+      "operating_point_overlay_i_range": "~A",
+      "operating_point_overlay_v_precision": 3,
+      "operating_point_overlay_v_range": "~V",
+      "overbar_offset_ratio": 1.23,
+      "pin_symbol_size": 25.0,
+      "text_offset_ratio": 0.15
+    },
+    "legacy_lib_dir": "",
+    "legacy_lib_list": [],
+    "meta": {
+      "version": 1
+    },
+    "net_format_name": "",
+    "page_layout_descr_file": "",
+    "plot_directory": "",
+    "spice_current_sheet_as_root": false,
+    "spice_external_command": "spice \"%I\"",
+    "spice_model_current_sheet_as_root": true,
+    "spice_save_all_currents": false,
+    "spice_save_all_dissipations": false,
+    "spice_save_all_voltages": false,
+    "subpart_first_id": 65,
+    "subpart_id_separator": 0
+  },
+  "sheets": [
+    [
+      "7c670055-6eae-4e4c-be40-3c8d8a0ecd74",
+      "Root"
+    ]
+  ],
+  "text_variables": {}
+}