arduino lowbyte and highbyte functions - arduino

Question

int i;
float number=123.456;
void setup()
{
Serial.begin(9600);
}
void loop()
{
byte a;
a=lowByte(number);
//is this the way i extract the right most byte from a 4 bytes float? equating a byte named a with the function lowByte? Is this how i use the lowByte function? cos i couldnt compile this in my arduino IDE.
delay(1000);
}
/*
what i am trying to do is to transmit float 123.456 over zigbee. and i believe data transmission is done byte by byte. so what i am trying to do is to break this float up into 4 bytes and send them byte by byte. how i do it is i intend to use lowbyte. then i just bitshfit by 8 bits (equivalent to 1 byte) to the right. then i use lowByte again. then again bitshift by 8 and lowByte and the repeat the process until i capture all 4 bytes.
so what i want to find out is how do i break the float into 4 bytes? and store these values for them to be sent?
can it be done in a byte array?
*/

Answer 1

I wanted to to the exact same thing and i found the below would work.
One approach is to use a union that stores the float value along with a unsigned char array. For example:
union v {
float f;
unsigned char uc[4];
};
union v val;
float f;
extern void store_byte (unsigned char v);
void test (void) {
val.f = 34.567; // set floating point value
store_byte (val.uc[0]); // write access to the bytes of the float value
store_byte (val.uc[1]);
store_byte (val.uc[2]);
store_byte (val.uc[3]);
val.uc[0] = 0x3F; // set float value (1.1)
val.uc[1] = 0x8C;
val.uc[2] = 0xCC;
val.uc[3] = 0xCD;
f = val.f; // read the value as FLOAT type.
}