Using the last element of an array cause me troubles

[hugo007]

Hello
I have a function that computes an CRC code using this code

Code: [Select]



byte dataBusOut[5]= {0x01,0x7b,0x7f,0x00,0x04};//start byte , ID, message, CRC ,End Byte --max usable values

byte checkCrc( byte startByte, byte id, byte message , byte endByte)
{  
 Serial.println(startByte,HEX);//To test the element
 Serial.println(id,HEX);//To test the element
 Serial.println(message,HEX);//To test the element
 Serial.println(endByte,HEX);//Bad element sometimes
 byte crcCalc = startByte +id + message + endByte;  
 return crcCalc;  
 
}
This code works but what is bugging me is the array elements.I just need 5 elements to put data but if I declared the array byte dataBusOut[4] which will have space for 5 elements the last element gets changed somehow causing the CRC to get diferent values from the same data.If I declare it byte dataBusOut[5] it works well.
what I am missing here

[Arrch]

byte data[4] gives you four elements: 0, 1, 2, & 3
byte data[5] gives you five elements: 0, 1, 2, 3, & 4

[majenko]

byte dataBusOut[4] has space for 4 elements (0 to 3).

byte dataBusOut[5] has space for 5 elements (0 to 4).

You are getting confused between the array size and the array range.

[hugo007]

Yes you are right.How can't I see that
Thanks