Insert an integer and convert into HEX array

Using Arduino Programming Questions
#1

Hi I have a HEX array like this:

uint8_t my_serial_bytes={0x55, 0x01, 0x00};

Now I want to create a function to update a HEX in this array. For example:

void changeVal(int val){
my_serial_bytes[1]=val;
}

changeVal(30); //my_serial_bytes[0x55, 0x1E, 0x00];

So if I call function “changeVal(30);”, The array will become my_serial_bytes[0x55, 0x1E, 0x00];

How do I do this? Thanks a lot for any inputs.

#2

What's wrong with the approach you've outlined?

#3

Keep in mind that HEX is just a human readable way of representing a binary number, which is how it is stored.

#4

Here is my script:

char incomingByte = 0;
uint8_t my_serial_bytes={0x55, 0x01, 0xF0};

void setup() {
Serial.begin(9600);
}

void loop() {
if (Serial.available() > 0) {
incomingByte = Serial.read();
Serial.println(my_serial_bytes[1]);
changeVal(incomingByte);
Serial.println(my_serial_bytes[1]);
}
}
void changeVal(int val){
my_serial_bytes[1]=val;
}

If I type in 1, it comes out
1
49
not
1
1
Seems like I need to convert to integer?

#5

Quote tags are not code tags!

That’s because you use serial/Serial monitor. You don’t input 1, you input ‘1’, the ASCII char for a 1 character. And that has the value of 49 in decimal. If you only want numbers between 0 and 9 it’s an easy fix.

uint8_t my_serial_bytes[]={0x55, 0x01, 0xF0};

void setup() {
  Serial.begin(9600);
}

void loop() {
  if (Serial.available() > 0) {
    Serial.println(my_serial_bytes[1]);
    changeVal(Serial.read() - '0');
    Serial.println(my_serial_bytes[1]);
  }
}
void changeVal(uint8_t val){
   my_serial_bytes[1]=val;
}

If you want bigger numbers to input via Serial it’s more difficult.

#6

A "1" on your keyboard is an ASCII "49". That is how characters are stored internally on a computer. You could not only solve your problem, but learn a bunch by reading up on ASCII. Serial.print() is an overloaded function, it adapts itself to the datatype that you pass to it. You passed it a uint8_t, so it printed the value as an unsigned 8 bit integer, not an ASCII character.

The atoi() function converts from numbers like ASCII "1" to the numerical value 1. Or "123" to 123.

There is no such thing as a "hex array". Not in C. Hex is a human readable format for binary data. You can type, read and think in hex, but the computer stores everything in pure binary.

#7

Numbers are not hex or decimal. Nether are they binary, roman numerals, or Sumerian cuneiform. Numbers are numbers. Hex is simply the way we write them down.

#8