Speed versus Temerature

[ghost]

Nice little project!
Add a resistor to heat it up a bit, and a temperature sensor. You will see crazy changes in speed with the temperatures.
Need very slow UART speeds with internal clock if for instance u
sing it outdoors.

[wagiminator]

Hi and thanks! You are right, in addition to the supply voltage, the temperature is crucial. The idea behind the solution with the ISCP connection is that you first run the target MCU with its corresponding software under the conditions under which it is intended. When the MCU has reached "operating temperature", you press the button and the oscillator is then calibrated under the "real conditions".