qmk-firmware/drivers/avr/apa102.c

/*
* APA102 lib V1.0a
*
* Controls APA102 RGB-LEDs
* Author: Mikkel (Duckle29 on github)
*
* Dec 22th, 2017  v1.0a Initial Version
*
* 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 2 of the License, or
* (at your option) any later version.
*
* 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 <http://www.gnu.org/licenses/>.
*/

#include "apa102.h"
#include <avr/interrupt.h>
#include <avr/io.h>
#include <util/delay.h>
#include "debug.h"

// Setleds for standard RGB
void inline apa102_setleds(LED_TYPE *ledarray, uint16_t leds){
  apa102_setleds_pin(ledarray,leds, _BV(RGB_DI_PIN & 0xF), _BV(RGB_CLK_PIN & 0xF));
}

void static inline apa102_setleds_pin(LED_TYPE *ledarray, uint16_t leds, uint8_t pinmask_DI, uint8_t pinmask_CLK){
  pinMode(RGB_DI_PIN, PinDirectionOutput);
  pinMode(RGB_CLK_PIN, PinDirectionOutput);

  apa102_send_array((uint8_t*)ledarray,leds)
}

void apa102_send_array(uint8_t *data, uint16_t leds){ // Data is struct of 3 bytes. RGB - leds is number of leds in data
  apa102_start_frame();
  while(leds--){
    apa102_send_frame(0xFF000000 | (data->b << 16) | (data->g << 8) | data->r);
    data++;
  }
  apa102_end_frame(leds);
}

void apa102_send_frame(uint32_t frame){
  for(uint32_t i=0xFF; i>0;){
    apa102_send_byte(frame & i);
    i = i << 8;
  }
}

void apa102_start_frame(){
  apa102_send_frame(0);
}

void apa102_end_frame(uint16_t leds)
{
  // This function has been taken from: https://github.com/pololu/apa102-arduino/blob/master/APA102.h
  // and adapted. The code is MIT licensed. I think thats compatible?

  // We need to send some more bytes to ensure that all the LEDs in the
  // chain see their new color and start displaying it.
  //
  // The data stream seen by the last LED in the chain will be delayed by
  // (count - 1) clock edges, because each LED before it inverts the clock
  // line and delays the data by one clock edge.  Therefore, to make sure
  // the last LED actually receives the data we wrote, the number of extra
  // edges we send at the end of the frame must be at least (count - 1).
  // For the APA102C, that is sufficient.
  //
  // The SK9822 only updates after it sees 32 zero bits followed by one more
  // rising edge.  To avoid having the update time depend on the color of
  // the last LED, we send a dummy 0xFF byte.  (Unfortunately, this means
  // that partial updates of the beginning of an LED strip are not possible;
  // the LED after the last one you are trying to update will be black.)
  // After that, to ensure that the last LED in the chain sees 32 zero bits
  // and a rising edge, we need to send at least 65 + (count - 1) edges.  It
  // is sufficent and simpler to just send (5 + count/16) bytes of zeros.
  //
  // We are ignoring the specification for the end frame in the APA102/SK9822
  // datasheets because it does not actually ensure that all the LEDs will
  // start displaying their new colors right away.

  apa102_send_byte(0xFF);
  for (uint16_t i = 0; i < 5 + leds / 16; i++){
    apa102_send_byte(0);
  }
}

void apa102_send_byte(uint8_t byte){
  uint8_t i;
  for (i = 0; i < 8; i++){
    digitalWrite(RGB_DI_PIN, !!(byte & (1 << (7-i)));
    digitalWrite(RGB_CLK_PIN, PinLevelHigh);
  }
}