ser2neo/neopixel.cc

// NeoPixel ring driver.
//
// Copyright 2015 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
#include "neopixel.h"
#include "serial.h"

#include <avr/io.h>
#include <avr/interrupt.h>
#include <string.h>

extern Serial serial;

/// Initialise the hardware.
void NeoPixel::init() {
    DDRB |= _BV(1);
    TCCR0A = _BV(WGM01) | _BV(WGM00) | _BV(COM0B1) | _BV(COM0B0);
    TCCR0B = _BV(WGM02) | _BV(CS00);

    static_assert(Reload > 15, "Inter-bit time is probably too short.");
    OCR0A = Reload;
    OCR0B = Low;
}

/// Set all the LEDs to off and restart at the first LED.
void NeoPixel::clear() {
    p_ = bits_;
    memset(bits_, Low, sizeof(bits_));
}

/// Append a byte to the stream.
void NeoPixel::append(uint8_t b) {
    if (p_ <= (bits_ + sizeof(bits_) - Tail - BitsPerColour)) {
        for (auto i = 0; i < BitsPerColour; i++) {
            *p_++ = (b & 0x80) ? High : Low;
            b <<= 1;
        }
    }
}

/// Write to the LEDs.
void NeoPixel::write() {
    bits_[sizeof(bits_) - 1] = Stop;

    uint8_t *p = bits_;
    uint8_t *pend = bits_ + sizeof(bits_);

    cli();

    OCR0B = Stop;
    TIFR |= _BV(OCF0A);
    while (!(TIFR & _BV(OCF0A))) {
    }
    TIFR |= _BV(OCF0A);
    while (!(TIFR & _BV(OCF0A))) {
    }
    OCR0B = *p++;

    for (; p != pend; p++) {
        while (!(TIFR & _BV(OCF0A))) {
        }
        OCR0B = *p;
        TIFR |= _BV(OCF0A);
    }
    OCR0B = Stop;

    sei();
}