I've tried to modify some existing code to do what i want (make a 2 key keyboard) but i have no idea what the buf [2] actually means, Also the void releasekey at the end, what does that mean/do, Thanks very much all
uint8_t buf[8] = {
 0 };
#define PIN_Z 5
#define PIN_X 6
int state = 1;
void setup()
{
 Serial.begin(9600);
 pinMode(PIN_Z, INPUT);
 pinMode(PIN_X, INPUT);
 digitalWrite(PIN_Z, 1);
 digitalWrite(PIN_X, 1);
 delay(200);
}
void loop()
{
 state = digitalRead(PIN_Z);
 if (state != 1) {
  buf[2] = 29;
  Serial.write(buf, 8);
  releaseKey();
 }
 state = digitalRead(PIN_X);
 if (state != 1) {
  buf[2] = 27;
  Serial.write(buf, 8);
  releaseKey();
 }
}
void releaseKey()
{
 buf[0] = 0;
 buf[2] = 0;
 Serial.write(buf, 8);
 delay(100);
}
Even an aged and non-experienced programmer like I encounters this problem of counting -- should start counting from 0 or from 1.
Say, we have an LCD with 4 rows (4 lines). How should we refer to the Topmost line? Is it Line-1 or Line-0? If we use Line-1, we are using decimal counting style where the very first thing is addressed as number 1. It is fine as a natural way of counting and referring in human world. When we use Line-0, we are using indexing method where the very first thing is addressed as number 0. It is fine as a natural way of counting and referring in binary/programming world.
In programming, we remain strict to the style of counting. buf[3] refers to the element with index 3, and of course it is the 4th item of the array? Now the meanings are --
uint8_t buf[8]; stands for an array which has 8 elements (members); each member holds 8-bit unsigned quantity.
buf[0] refers to the member with index 0 (the very first item).
.......
buf[7] refers to the member with index 7 (the very last item).
The answer that you actually need is "go do a C++ tutorial". Google "C++ tutorial", and work your way through the first half - ignoring things that are specific to programs running on full machines (stdin/stdout, the String class, dynamic memory, using main() ). It will cover functions, arrays, variable scope and lifetime, basic stuff that you need to know.
You would only have 7 in a buf[8]. You need to have one more space for a null terminator.
The concept of the insertion (manual/auto) of null-byte comes when we are talking about char type array containing 8-bit values for which there are ASCII charcaters . Here, we have byte (uint8_t) type array containing byte (8-bit) values for which there may or may not corresponding ASCII characters.
void setup()
{
Serial.begin(9600);
char myArray[2] = {'A', 'B'}; //{'A', 'B', '\0'} //auto/manual insertion of null-byte
Serial.println(myArray); //allowed because of char keyword
byte xArray[2] = {0x41, 0x23}; //no auto insertion of null-byte and even not needed
//Serial.println(xArray); //not allowed because of uint8_t (byte) keyword.
}
void loop()
{
}
The concept of the [null terminator] comes when we are talking about char type array
Even then, you only need the null terminator if you're dealing with the char array collectively as a "C String"; it's the libc string functions that need the null terminator.
