#define VW_SPEED 500
#define VW_ID 54423
#define GPIO_TX 13 // GPIO передатчика

#define VW_HEADER_LEN 8
#define VW_MAX_MESSAGE_LEN 40
#define VW_MAX_PAYLOAD VW_MAX_MESSAGE_LEN-3
static uint8_t vw_tx_buf[(VW_MAX_MESSAGE_LEN * 2) + VW_HEADER_LEN]
     = {0x2a, 0x2a, 0x2a, 0x2a, 0x2a, 0x2a, 0x38, 0x2c};

const uint8_t symbols[] =
{
    0xd,  0xe,  0x13, 0x15, 0x16, 0x19, 0x1a, 0x1c,
    0x23, 0x25, 0x26, 0x29, 0x2a, 0x2c, 0x32, 0x34
};


#define lo8(x) ((x)&0xff)
#define hi8(x) ((x)>>8)
    uint16_t _crc_ccitt_update (uint16_t crc, uint8_t data)
    {
        data ^= lo8 (crc);
        data ^= data << 4;

        return ((((uint16_t)data << 8) | hi8 (crc)) ^ (uint8_t)(data >> 4)
                ^ ((uint16_t)data << 3));
    }

uint8_t vw_send(uint8_t* buf, uint8_t len)
{
// Number of symbols in vw_tx_buf to be sent;
uint8_t vw_tx_len = 0;

    uint8_t i;
    uint8_t index = 0;
    uint16_t crc = 0xffff;
    uint8_t *p = vw_tx_buf + VW_HEADER_LEN; // start of the message area
    uint8_t count = len + 3; // Added byte count and FCS to get total number of bytes

    if (len > VW_MAX_PAYLOAD)
    return false;

    // Encode the message length
    crc = _crc_ccitt_update(crc, count);
    p[index++] = symbols[count >> 4];
    p[index++] = symbols[count & 0xf];

    // Encode the message into 6 bit symbols. Each byte is converted into
    // 2 6-bit symbols, high nybble first, low nybble second
    for (i = 0; i < len; i++)
    {
    crc = _crc_ccitt_update(crc, buf[i]);
    p[index++] = symbols[buf[i] >> 4];
    p[index++] = symbols[buf[i] & 0xf];
    }

    // Append the fcs, 16 bits before encoding (4 6-bit symbols after encoding)
    // Caution: VW expects the _ones_complement_ of the CCITT CRC-16 as the FCS
    // VW sends FCS as low byte then hi byte
    crc = ~crc;
    p[index++] = symbols[(crc >> 4)  & 0xf];
    p[index++] = symbols[crc & 0xf];
    p[index++] = symbols[(crc >> 12) & 0xf];
    p[index++] = symbols[(crc >> 8)  & 0xf];

    // Total number of 6-bit symbols to send
    vw_tx_len = index + VW_HEADER_LEN;


 cli();

uint8_t vw_tx_bit = 0,vw_tx_index=0;
    for (; vw_tx_index < vw_tx_len;)
    {

digitalWrite(GPIO_TX , vw_tx_buf[vw_tx_index] & (1 << vw_tx_bit++));

        if (vw_tx_bit >= 6)
        {
                vw_tx_index++;
        vw_tx_bit = 0;
        }

delayMicroseconds((1000000/VW_SPEED));

    }
    digitalWrite(GPIO_TX , 0);

    sei();

    return true;
}

uint8_t countsend;


void setup()
{


pinMode(GPIO_TX, OUTPUT);


}

void loop()
{

int16_t hum=610;  // 60.0%
int16_t temp=253; // 25.3 С



uint8_t msg[]={26,VW_ID&255,VW_ID/256,countsend,

      1, temp&255,temp/256, // датчик температуры
      2, hum&255,hum/256 // датчик влажности

};

    vw_send((uint8_t *)msg, sizeof(msg));


    countsend++; // счетчик передач

    delay(5000);
}