 // G0-H3 - humidity written backwards as 100 - HUMIDITY in two's compliment code, for example:
 //          1110|1011 = 59% because 101001 (inverted all bits and add 1) = 41, and 100 - 41 = 59
 //
-// I0-I3 - 4 less significant bits of check sum of the tetrads T1-T8 written backwards.
+// I0-I3 - 4 check sum which is calculated as a sum of less significant bits
+//            of check sum of the tetrads T1-T8 written backwards.
 //            for example let's look at the example message:
-//            1011|1100|0000|0101|0011|0000|0001|1011|1101
-//            sum of the tetrad T1-T8 = 101011, lets take last 4 bits and wrote them backward:
-//            1101 which is equal T9 tetrad
+//            1011|1100|0100|0000|1111|0000|0010|1111|0010
+//            sum of the tetrad T1-T8 where each bit written backwards = 110100,
+//            lets take last 4 bits and wrote them backward:
+//            0010 which is equal to T9 tetrad
 
 volatile byte data[DATA_ARRAY_SIZE] = {0, 0, 0, 0, 0, 0, 0, 0, 0};
 

    //Sum first 8 tetrads
    int sum = 0;
    for (byte i = 0; i < DATA_ARRAY_SIZE - 1; i++) {
        sum += (int)data[i];
    }

    //returns true if calculated check sum matches received
