obtain a single output variable from the FOR loop
The data variable is the single output variable. Untested example.
int data = 0; // added **declare globally**
void display_pin_values()
{
//start marker
//Serial.print("<");
//Serial.print("Experiment:\r\n");
for (int i = 0; i < DATA_WIDTH; i++)
{
if ((pinValues >> i) & 1) {
Serial.print("1");
bitSet(data, i); // added
}
else
Serial.print("0");
bitClear(data, i); // added
}
//end marker
//Serial.print(">");
Serial.print("\r\n");
}