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20260614
0001-FireFly/firmware/ATTINY85_2026_MorseThrowie/ATTINY85_2026_MorseThrowie.ino

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/*
=============================================================================
FireFly Morse Throwie
- a light controlled (LED as Sensor) morse blinker throwie with ATTiny85
=============================================================================
Project definitions, sources
-----------------------------------------------------------------------------
Version: 0.3 - ATTiny85, 1 MHz, BOD fuse disabled
gitea : https://gitea.togo-lab.io/tgohle/0001-FireFly
Date : 2026-06-14
Key changes Version 0.3:
- Removed unnecessary ADC enable/disable from loop()
- Disabled ADC and analog comparator in setup()
- Added INPUT_PULLUP for unused Arduino pins 0, 1, 2 will save power
- Added safer watchdog setup with interrupt protection to save run near brownout
- Added wdt_reset() before sleep for cleaner 8 s timing
- Added lowercase-to-uppercase handling
- Unsupported characters are now ignored without adding fake timing gaps
-----------------------------------------------------------------------------
Inspired by Karl Lunt's FireFly project:
http://www.seanet.com/~karllunt/fireflyLED.html
Morse code reference:
'A', ".-" 'B', "-..." 'C', "-.-."
'D', "-.." 'E', "." 'F', "..-."
'G', "--." 'H', "...." 'I', ".."
'J', ".---" 'K', "-.-" 'L', ".-.."
'M', "--" 'N', "-." 'O', "---"
'P', ".--." 'Q', "--.-" 'R', ".-."
'S', "..." 'T', "-" 'U', "..-"
'V', "...-" 'W', ".--" 'X', "-..-"
'Y', "-.--" 'Z', "--.."
'1', ".----" '2', "..---" '3', "...--"
'4', "....-" '5', "....." '6', "-...."
'7', "--..." '8', "---.." '9', "----."
'0', "-----"
'.', ".-.-.-" ',', "--..--" '?', "..--.."
'!', "-.-.--" ':', "---..." ';', "-.-.-."
'(', "-.--." ')', "-.--.-" '"', ".-..-."
'@', ".--.-." '&', ".-..."
-----------------------------------------------------------------------------
Legal stuff / Copyright:
License_-_CC_BY-NC_4.0
https://creativecommons.org/licenses/by-nc/4.0/
-----------------------------------------------------------------------------
*/
#include <avr/sleep.h>
#include <avr/wdt.h>
#include <avr/pgmspace.h>
#include <avr/interrupt.h>
#include <string.h>
#ifndef cbi
#define cbi(sfr, bit) (_SFR_BYTE(sfr) &= ~_BV(bit))
#endif
#ifndef sbi
#define sbi(sfr, bit) (_SFR_BYTE(sfr) |= _BV(bit))
#endif
// ---------------------------------------------------------------------------
// Timing: unit length in ms.
// At 1 MHz, delay() is accurate when F_CPU=1000000L is set in boards.txt.
// 100 ms gives readable optical Morse; raise to 150 ms if readability is poor.
#define unitLength 100
// ---------------------------------------------------------------------------
// Sleep interval.
// Watchdog setup uses 8 s. For final use, change sleepCycles from 1 to 4
// for about 32 s between sensing/blinking activations.
const uint8_t sleepCycles = 4;
// ---------------------------------------------------------------------------
// LED pin definitions (N-side = cathode, P-side = anode for sensing/driving).
#define LED1_N_SIDE 3
#define LED1_P_SIDE 4
// ---------------------------------------------------------------------------
// ATTiny85 Arduino pins 0, 1, 2 are unused in actual design and physically open.
// Keep them in INPUT_PULLUP so they do not float and waste current.
#define UNUSED_PIN_0 0
#define UNUSED_PIN_1 1
#define UNUSED_PIN_2 2
// ---------------------------------------------------------------------------
// ATTiny85 has 512 bytes SRAM; this keeps the Morse text in flash.
// Only uppercase letters, digits, spaces, and the special chars in the switch
// below are emitted. Lowercase letters are converted to uppercase.
// Test setup: 20 x "0" because 0 = "-----" gives maximum LED ON time for test.
// shorter text will better, more text will cost more power.
const char morseText[] PROGMEM = "TOGO LAB";
// Ruler: 0....0....1...1....2
// Ruler: 0....5....0...5....0
// ---------------------------------------------------------------------------
// Darkness threshold.
// Higher value = triggers in brighter conditions.
// Best calibrated at actual dusk/dawn with the chosen LED type.
const unsigned int darknessThreshold = 17000;
// ---------------------------------------------------------------------------
// Watchdog interrupt flag — volatile because it is written in an ISR.
volatile bool f_wdt = true;
// ---------------------------------------------------------------------------
// Forward declarations.
void setup_watchdog(uint8_t ii);
void system_sleep();
void configureUnusedPins();
void releaseLedPins(int LED_N, int LED_P);
unsigned int sensDarkness(int LED_N, int LED_P);
void morse(int LED_N, int LED_P);
void dit(int LED_P);
void dah(int LED_P);
// ===========================================================================
// Setup
// ===========================================================================
void setup()
{
// Disable unused peripherals immediately to save power.
// PRTIM1, PRUSI: unused, safe to gate off.
// PRADC: ADC is not used; LED sensing is done with digitalRead().
// PRTIM0: must stay ON while awake because delay() depends on Timer0.
PRR = (1 << PRTIM1) | (1 << PRUSI) | (1 << PRADC);
// ADC off. It is not needed for digitalRead()-based LED sensing.
cbi(ADCSRA, ADEN);
// Analog comparator off. Saves a little sleep current.
ACSR |= (1 << ACD);
configureUnusedPins();
releaseLedPins(LED1_N_SIDE, LED1_P_SIDE);
setup_watchdog(9); // 8-second watchdog interval.
}
// ===========================================================================
// Main loop
// ===========================================================================
void loop()
{
if (f_wdt) {
f_wdt = false;
if (sensDarkness(LED1_N_SIDE, LED1_P_SIDE) > darknessThreshold) {
morse(LED1_N_SIDE, LED1_P_SIDE);
}
// Return LED pins to high-Z before sleeping.
// Internal pullups stay disabled for the LED pins.
releaseLedPins(LED1_N_SIDE, LED1_P_SIDE);
}
// Test setup: 1 x 8 s sleep.
// Final setup: set sleepCycles = 4 for about 32 s.
for (uint8_t i = 0; i < sleepCycles; i++) {
system_sleep();
}
}
// ===========================================================================
// Pin helpers
// ===========================================================================
void configureUnusedPins()
{
pinMode(UNUSED_PIN_0, INPUT_PULLUP);
pinMode(UNUSED_PIN_1, INPUT_PULLUP);
pinMode(UNUSED_PIN_2, INPUT_PULLUP);
}
void releaseLedPins(int LED_N, int LED_P)
{
// digitalWrite LOW before INPUT disables the internal pullup on Arduino cores.
digitalWrite(LED_N, LOW);
digitalWrite(LED_P, LOW);
pinMode(LED_N, INPUT);
pinMode(LED_P, INPUT);
}
// ===========================================================================
// Sleep helpers
// ===========================================================================
void system_sleep()
{
// Reset watchdog counter so each sleep cycle starts with a fresh interval.
wdt_reset();
set_sleep_mode(SLEEP_MODE_PWR_DOWN);
// Atomic sleep entry pattern.
// After sei(), AVR executes the next instruction before servicing interrupts,
// so sleep_cpu() is not skipped by a just-pending interrupt.
cli();
sleep_enable();
sei();
sleep_cpu();
// WDT interrupt wakes the CPU here.
sleep_disable();
}
// Watchdog setup - ii selects timeout:
// 0=16ms 1=32ms 2=64ms 3=128ms 4=250ms 5=500ms
// 6=1s 7=2s 8=4s 9=8s
void setup_watchdog(uint8_t ii)
{
if (ii > 9) ii = 9;
uint8_t bb = ii & 7;
if (ii > 7) bb |= (1 << WDP3);
uint8_t oldSREG = SREG;
cli();
wdt_reset();
MCUSR &= ~(1 << WDRF);
// Timed sequence: enable configuration change, then set interrupt-only WDT.
WDTCR |= (1 << WDCE) | (1 << WDE);
WDTCR = bb | (1 << WDIE);
SREG = oldSREG;
}
ISR(WDT_vect)
{
f_wdt = true;
}
// ===========================================================================
// Light sensor
// ===========================================================================
// Returns a "darkness level": higher = darker.
// Charges the LED junction capacitance, then times how long it takes to bleed
// back through the reverse-biased LED until the input reads LOW.
// ~30000 = pitch black, ~0 = bright light
unsigned int sensDarkness(int LED_N, int LED_P)
{
unsigned int i;
// Charge the LED junction capacitance.
pinMode(LED_N, OUTPUT);
pinMode(LED_P, OUTPUT);
digitalWrite(LED_N, HIGH);
digitalWrite(LED_P, LOW);
// Let the N-side float and measure bleed-down time.
pinMode(LED_N, INPUT);
digitalWrite(LED_N, LOW); // disable internal pullup
for (i = 0; i < 30000; i++) {
if (digitalRead(LED_N) == LOW) break;
}
// Clean up after sensing: both LED pins low, then caller releases them.
pinMode(LED_N, OUTPUT);
digitalWrite(LED_N, LOW);
pinMode(LED_P, OUTPUT);
digitalWrite(LED_P, LOW);
return i;
}
// ===========================================================================
// Morse helpers
// ===========================================================================
void dit(int LED_P)
{
digitalWrite(LED_P, HIGH);
delay(unitLength);
digitalWrite(LED_P, LOW);
delay(unitLength);
}
void dah(int LED_P)
{
digitalWrite(LED_P, HIGH);
delay(unitLength * 3);
digitalWrite(LED_P, LOW);
delay(unitLength);
}
// ===========================================================================
// Morse sender
// ===========================================================================
void morse(int LED_N, int LED_P)
{
pinMode(LED_N, OUTPUT);
pinMode(LED_P, OUTPUT);
digitalWrite(LED_N, LOW);
digitalWrite(LED_P, LOW);
const size_t len = strlen_P(morseText);
for (size_t i = 0; i < len; i++) {
char c = (char)pgm_read_byte(&morseText[i]);
// Allow lowercase source text without silently breaking timing.
if (c >= 'a' && c <= 'z') {
c = c - 'a' + 'A';
}
bool symbolSent = false;
switch (c)
{
// ----- Letters -----
case 'A': dit(LED_P); dah(LED_P); symbolSent = true; break; // .-
case 'B': dah(LED_P); dit(LED_P); dit(LED_P); dit(LED_P); symbolSent = true; break; // -...
case 'C': dah(LED_P); dit(LED_P); dah(LED_P); dit(LED_P); symbolSent = true; break; // -.-.
case 'D': dah(LED_P); dit(LED_P); dit(LED_P); symbolSent = true; break; // -..
case 'E': dit(LED_P); symbolSent = true; break; // .
case 'F': dit(LED_P); dit(LED_P); dah(LED_P); dit(LED_P); symbolSent = true; break; // ..-.
case 'G': dah(LED_P); dah(LED_P); dit(LED_P); symbolSent = true; break; // --.
case 'H': dit(LED_P); dit(LED_P); dit(LED_P); dit(LED_P); symbolSent = true; break; // ....
case 'I': dit(LED_P); dit(LED_P); symbolSent = true; break; // ..
case 'J': dit(LED_P); dah(LED_P); dah(LED_P); dah(LED_P); symbolSent = true; break; // .---
case 'K': dah(LED_P); dit(LED_P); dah(LED_P); symbolSent = true; break; // -.-
case 'L': dit(LED_P); dah(LED_P); dit(LED_P); dit(LED_P); symbolSent = true; break; // .-..
case 'M': dah(LED_P); dah(LED_P); symbolSent = true; break; // --
case 'N': dah(LED_P); dit(LED_P); symbolSent = true; break; // -.
case 'O': dah(LED_P); dah(LED_P); dah(LED_P); symbolSent = true; break; // ---
case 'P': dit(LED_P); dah(LED_P); dah(LED_P); dit(LED_P); symbolSent = true; break; // .--.
case 'Q': dah(LED_P); dah(LED_P); dit(LED_P); dah(LED_P); symbolSent = true; break; // --.-
case 'R': dit(LED_P); dah(LED_P); dit(LED_P); symbolSent = true; break; // .-.
case 'S': dit(LED_P); dit(LED_P); dit(LED_P); symbolSent = true; break; // ...
case 'T': dah(LED_P); symbolSent = true; break; // -
case 'U': dit(LED_P); dit(LED_P); dah(LED_P); symbolSent = true; break; // ..-
case 'V': dit(LED_P); dit(LED_P); dit(LED_P); dah(LED_P); symbolSent = true; break; // ...-
case 'W': dit(LED_P); dah(LED_P); dah(LED_P); symbolSent = true; break; // .--
case 'X': dah(LED_P); dit(LED_P); dit(LED_P); dah(LED_P); symbolSent = true; break; // -..-
case 'Y': dah(LED_P); dit(LED_P); dah(LED_P); dah(LED_P); symbolSent = true; break; // -.--
case 'Z': dah(LED_P); dah(LED_P); dit(LED_P); dit(LED_P); symbolSent = true; break; // --..
// ----- Digits -----
case '1': dit(LED_P); dah(LED_P); dah(LED_P); dah(LED_P); dah(LED_P); symbolSent = true; break; // .----
case '2': dit(LED_P); dit(LED_P); dah(LED_P); dah(LED_P); dah(LED_P); symbolSent = true; break; // ..---
case '3': dit(LED_P); dit(LED_P); dit(LED_P); dah(LED_P); dah(LED_P); symbolSent = true; break; // ...--
case '4': dit(LED_P); dit(LED_P); dit(LED_P); dit(LED_P); dah(LED_P); symbolSent = true; break; // ....-
case '5': dit(LED_P); dit(LED_P); dit(LED_P); dit(LED_P); dit(LED_P); symbolSent = true; break; // .....
case '6': dah(LED_P); dit(LED_P); dit(LED_P); dit(LED_P); dit(LED_P); symbolSent = true; break; // -....
case '7': dah(LED_P); dah(LED_P); dit(LED_P); dit(LED_P); dit(LED_P); symbolSent = true; break; // --...
case '8': dah(LED_P); dah(LED_P); dah(LED_P); dit(LED_P); dit(LED_P); symbolSent = true; break; // ---..
case '9': dah(LED_P); dah(LED_P); dah(LED_P); dah(LED_P); dit(LED_P); symbolSent = true; break; // ----.
case '0': dah(LED_P); dah(LED_P); dah(LED_P); dah(LED_P); dah(LED_P); symbolSent = true; break; // -----
// ----- Punctuation -----
case '.': dit(LED_P); dah(LED_P); dit(LED_P); dah(LED_P); dit(LED_P); dah(LED_P); symbolSent = true; break; // .-.-.-
case ',': dah(LED_P); dah(LED_P); dit(LED_P); dit(LED_P); dah(LED_P); dah(LED_P); symbolSent = true; break; // --..--
case '?': dit(LED_P); dit(LED_P); dah(LED_P); dah(LED_P); dit(LED_P); dit(LED_P); symbolSent = true; break; // ..--..
case '!': dah(LED_P); dit(LED_P); dah(LED_P); dit(LED_P); dah(LED_P); dah(LED_P); symbolSent = true; break; // -.-.--
case ':': dah(LED_P); dah(LED_P); dah(LED_P); dit(LED_P); dit(LED_P); dit(LED_P); symbolSent = true; break; // ---...
case ';': dah(LED_P); dit(LED_P); dah(LED_P); dit(LED_P); dah(LED_P); dit(LED_P); symbolSent = true; break; // -.-.-.
case '(': dah(LED_P); dit(LED_P); dah(LED_P); dah(LED_P); dit(LED_P); symbolSent = true; break; // -.--.
case ')': dah(LED_P); dit(LED_P); dah(LED_P); dah(LED_P); dit(LED_P); dah(LED_P); symbolSent = true; break; // -.--.-
case '"': dit(LED_P); dah(LED_P); dit(LED_P); dit(LED_P); dah(LED_P); dit(LED_P); symbolSent = true; break; // .-..-.
case '@': dit(LED_P); dah(LED_P); dah(LED_P); dit(LED_P); dah(LED_P); dit(LED_P); symbolSent = true; break; // .--.-.
case '&': dit(LED_P); dah(LED_P); dit(LED_P); dit(LED_P); dit(LED_P); symbolSent = true; break; // .-...
// Space handling:
// Previous symbol already ended with 1 unit OFF and then received the
// normal 2 unit character gap. Add 4 units here -> total word gap 7 units.
case ' ':
delay(unitLength * 4);
break;
// Unsupported chars are ignored without adding an artificial gap.
default:
break;
}
// Inter-character gap: 3 units total.
// dit()/dah() already trail 1 unit OFF, so add the remaining 2 units.
if (symbolSent) {
delay(unitLength * 2);
}
}
digitalWrite(LED_P, LOW);
digitalWrite(LED_N, LOW);
}
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