Hi jremington, just to close the loop on this issue. I got the solution by casting a string into the uint8_t variable ... I was stuck the other way around trying to sort out the issue from the char copying approach. Thanks for your advice!
Test of proof and code that might be helpful to others, as follows:
uint8_t key_array[16];
uint8_t message_array[16];
int i;
String inputt = "65D0F7758B094114AFA6D33A5EA0716AF8EC2769085E888FA68FC6309FA0451E";
String inputtKey="";
String inputtMessage="";
void setup()
{
Serial.begin(9600);
while (!Serial);
Serial.println("Present Sketch name -> casting3.ino ");
Serial.println("");
}
void loop()
{
Serial.print("initial string to convert .. ");Serial.println(inputt);
Serial.println("");
inputtKey = inputt.substring(0,inputt.length()-32);
inputtMessage = inputt.substring(32,inputt.length());
Serial.print("KEY part in the POST .. ");Serial.print(inputtKey);Serial.println(" -> As a String");
Serial.print("MESSAGE part in the POST .. ");Serial.print(inputtMessage);Serial.println(" -> As a String");
Serial.println("");
// converting each pair of char into hexadecimal for uint8_t type
for ( i = 0; i < 32; i += 2)
{
key_array[i/2] = (uint8_t)strtol(inputtKey.substring(i, i+2).c_str(), NULL, 16);
}
for ( i = 0; i < 32; i += 2)
{
message_array[i/2] = (uint8_t)strtol(inputtMessage.substring(i, i+2).c_str(), NULL, 16);
}
// printing the outputs
Serial.println("Final Outputs");
Serial.println("+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ ");
Serial.print("KEY .. ");printHex(key_array,16);Serial.println(" -> as uint8_t");
Serial.print("MESSAGE .. ");printHex(message_array,16);Serial.println(" -> as uint8_t");
while(1);
}
void printHex(uint8_t *text, size_t size)
{
for (byte i = 0; i < size; i = i + 1)
{
if (text[i] < 16)
{
Serial.print("0");
}
Serial.print(text[i], HEX);
}
}