}

else {

Serial.print ("\ncheck sum error! sum=");

Serial.println (getsum_add (receive_ACK, 25), HEX);

}

}

//if check sum is ok

boolean checksum () {

uint8_t checksum = getsum_add (receive_ACK, 25);

if (checksum == receive_ACK[25])

return true;

else

return false;

}

//read 2 byte to uint16_t

uint16_t read_uint8_t (uint8_t *buffer, uint8_t sub) {

// Big-Endian,

first byte is high byte

return ((uint16_t)(buffer[sub]) << 8) + buffer[sub + 1];

}

//get check sum, add from 0 to length-1

uint8_t getsum_add (uint8_t *buffer, uint8_t length) {

uint8_t sum;

for (int i = sum = 0; i < length; i++) {

sum += buffer[i];

}

return sum;

}

/****************************************************************************

***/

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