OK, took some time today, ran a few tests with essentially some variations on the following code.
volatile char UUID[] = "<UUID=da51a9f0-9a49-11e0-aa80-0800200c9a66>";
char version[] = "UUID_TEST 0.04";
void setup()
{
Serial.begin(115200);
Serial.println(version);
UUID[0] = UUID[0];
}
void loop(){}
Then I retrieved the whole 32K image with [dosbox windows 7]
cd C:\Program Files (x86)\arduino-0021\hardware\tools\avr\bin>
avrdude -C "C:\Program Files (x86)\arduino-0022\hardware\tools\avr\etc\avrdude.conf" -v -v -v -v -p atmega328p -c stk500 -U flash:r:"C:/arduino.bin":r -P\\.\COM5 -b57600
viewing the binary easily reveals the UUID. See picture attached.
Some notes:
The UUID array must be volatile and the assignment UUID[0] = UUID[0] are needed both otherwise the compiler optimizes it away.
size without UUID string: 1908 bytes
size with UUID string: 1960 bytes
so this proof of concept implementation took 52 bytes.
- Remove the tag structure <UUID=...> (-7) => 45 bytes
- Remove - signs in the UUID (-4) => 41 bytes
- Make the UUID binary (-17) => 24 bytes.
proof is in the pudding test:
volatile uint8_t UUID[] = { 0x65, 0x65, 0x65, 0x65, 0x65, 0x65, 0x65, 0x65,
0x65, 0x65, 0x65, 0x65, 0x65, 0x65, 0x65, 0x65 }; // character e 16 times
char version[] = "UUID_TEST 0.06";
void setup()
{
Serial.begin(115200);
Serial.println(version);
UUID[0] = UUID[0];
}
void loop(){}
size without UUID uint8_t array : 1908 bytes
size with UUID uint8_t array: 1932 bytes
so UUID signature now takes 24 bytes.
OK tinkered enough 
Rob
