/**
 * Project: AVR ATtiny USB Tutorial at http://codeandlife.com/
 * Author: Joonas Pihlajamaa, joonas.pihlajamaa@iki.fi
 * Inspired by V-USB example code by Christian Starkjohann
 * Copyright: (C) 2012 by Joonas Pihlajamaa
 * License: GNU GPL v3 (see License.txt)
 */
#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/wdt.h>
#include <stdint.h>
#include <util/delay.h>

#include "usbdrv.h"

#define USB_DATA_OUT 2
#define USB_DATA_IN 4

#define BUFER_SIZE 8
static uchar replyBuf[BUFER_SIZE];
static uchar dataReceived = 0;
static uchar dataLength = 0;
static uchar updated = 0;

// this gets called when custom control message is received
USB_PUBLIC uchar usbFunctionSetup(uchar data[8]) {
    usbRequest_t *rq = (void *)data; // cast data to correct type

    switch(rq->bRequest) { // custom command is in the bRequest field
    case USB_DATA_OUT: // send data to PC
        usbMsgPtr = replyBuf;
        return sizeof(replyBuf);
    case USB_DATA_IN: // receive data from PC
        dataLength  = (uchar)rq->wLength.word;
        dataReceived = 0;

        if(dataLength  > sizeof(replyBuf)) // limit to buffer size
            dataLength  = sizeof(replyBuf);

        return USB_NO_MSG; // usbFunctionWrite will be called now
    }

    return 0; // should not get here
}

USB_PUBLIC uchar usbFunctionWrite(uchar *data, uchar len) {
	uchar i;
    for(i = 0; dataReceived < dataLength && i < len; i++, dataReceived++) {
        replyBuf[dataReceived] = data[i];
	}
    if (dataReceived == dataLength) {
        updated = 1;
    }
    return (dataReceived == dataLength); // 1 if we received it all, 0 if not
}

#define abs(x) ((x) > 0 ? (x) : (-x))

// Called by V-USB after device reset
void hadUsbReset() {
    int frameLength, targetLength = (unsigned)(1499 * (double)F_CPU / 10.5e6 + 0.5);
    int bestDeviation = 9999;
    uchar trialCal, bestCal = 0, step, region;

    // do a binary search in regions 0-127 and 128-255 to get optimum OSCCAL
    for(region = 0; region <= 1; region++) {
        frameLength = 0;
        trialCal = (region == 0) ? 0 : 128;

        for(step = 64; step > 0; step >>= 1) {
            if(frameLength < targetLength) // true for initial iteration
                trialCal += step; // frequency too low
            else
                trialCal -= step; // frequency too high

            OSCCAL = trialCal;
            frameLength = usbMeasureFrameLength();

            if(abs(frameLength-targetLength) < bestDeviation) {
                bestCal = trialCal; // new optimum found
                bestDeviation = abs(frameLength -targetLength);
            }
        }
    }

    OSCCAL = bestCal;
}

#define LED_PIN PB1
#define LED_PORT B

#define CONCAT(a, b)            a ## b
#define CONCAT_EXP(a, b)   CONCAT(a, b)
#define LED_PORTREG  CONCAT_EXP(PORT,LED_PORT)
#define LED_DDRREG   CONCAT_EXP(DDR,LED_PORT)
#define LED_BIT_VAL     (1 << PB1)



void LED_init() {
    LED_PORTREG &= ~LED_BIT_VAL;
    LED_DDRREG |= LED_BIT_VAL;
}

void LED_reset() {
    LED_PORTREG &= ~LED_BIT_VAL;
    _delay_us(40);
}

void __attribute__((always_inline)) inline LED_byte(uint8_t byte) {
    volatile uint8_t counter = 8;
    asm volatile (
      "1:                     \n\t"
      "sbi %1, 0x01           \n\t"       // 2 CLK  (high)
      "rjmp .+0               \n\t"       // 2 CLK
      "rol %2                 \n\t"       // 1 CLK
      "brcs 2f                \n\t"       // 2 CLK
      // highest bit not set => go low
      "cbi %1, 0x01           \n\t"       // 2 CLK  (low)
      "rjmp .+0               \n\t"       // 2 CLK
      "rjmp .+0               \n\t"       // 2 CLK
      "rjmp .+0               \n\t"       // 2 CLK
      "rjmp .+0               \n\t"       // 2 CLK
      "rjmp .+0               \n\t"       // 2 CLK
      "rjmp .+0               \n\t"       // 2 CLK
      "rjmp .+0               \n\t"       // 2 CLK
      "nop                    \n\t"       // 1 CLK
      "rjmp 3f                \n\t"       // 2 CLK
      "2:                     \n\t"
      // highest bit set => stay high
      "rjmp .+0               \n\t"       // 2 CLK
      "rjmp .+0               \n\t"       // 2 CLK
      "rjmp .+0               \n\t"       // 2 CLK
      "rjmp .+0               \n\t"       // 2 CLK
      "rjmp .+0               \n\t"       // 2 CLK
      "rjmp .+0               \n\t"       // 2 CLK
      "rjmp .+0               \n\t"       // 2 CLK
      "nop                    \n\t"       // 1 CLK
      "cbi %1, 0x01           \n\t"       // 2 CLK  (low)
      "3:                     \n\t"
      "nop                    \n\t"       // 1 CLK
      "dec %0                 \n\t"       // 1 CLK
      "brne 1b                \n\t"       // 1/2 CLK
      // code after 8 bits
      :
      : "r" (counter), "I" (_SFR_IO_ADDR(PORTB)), "r" (byte)
      :
    );
}

void LED_color(uchar r, uchar g, uchar b) {
    LED_byte(r);
    LED_byte(g);
    LED_byte(b);
    LED_reset();
}

int main() {
    uchar i;
    LED_init();
    LED_color(255,0,0);

    wdt_enable(WDTO_1S); // enable 1s watchdog timer

    usbInit();

    usbDeviceDisconnect(); // enforce re-enumeration
    for(i = 0; i<250; i++) { // wait 500 ms
        wdt_reset(); // keep the watchdog happy
        _delay_ms(2);
    }

    usbDeviceConnect();

    sei(); // Enable interrupts after re-enumeration

    while(1) {
        wdt_reset(); // keep the watchdog happy
        usbPoll();
        if (updated == 1) {
            cli();
            LED_color(replyBuf[0], replyBuf[1], replyBuf[2]);
            sei();
            replyBuf[3] = 'O';
            replyBuf[4] = 'K';
            replyBuf[5] = '!';
            updated = 0;
        }
    }

    return 0;
}