Facepalm of the day

I wrote this code for my red alert box and tested it using a shorter timeout than 60 seconds--it worked fine with a 10-second timeout. Just today I realized that the 60s timeout wasn't working; even after several minutes without communication, the globe was still showing green. The cause of the bug is left to the reader, but a hint is available if you click "more inside".

void loop()
{
    unsigned long now = millis(); // time since boot in milliseconds

    if(Serial.available()) {
        level = Serial.read() % 4;
        last_message = now;
    } else if(now - last_message > 60*1000 && level < 3) {
        // if no message received after 60*1000 ms, increase alert level
        last_message = now; // well, sorta
        level ++;
    }

    if(level != oldlevel) {
        set_led_color(level);
        oldlevel = level;
    }
    delay(50);
}

Hint: sizeof(int) == 2 on avr

Entry first conceived on 13 March 2009, 1:33 UTC, last modified on 15 January 2012, 3:46 UTC
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