Some of the major updates in the firmware... (more to come)

V1.35:
- Fixed PID calculator coefficients and sampling (it could have had oscillations)
- PID tested with 12V in and duty 110-220 with low and high resistance cable, acceptable performance in all cases
- Missing to correct refresh rate of the screen (it is increased as the main loop is executed more times)

V1.4:
- Added channel tracking option in menu. Now it is possible to set one channel temperature, and both are set.

V1.5:
- Added AutoON function in menu: When changing tip, the channel goes on automatically to the set temperature.

V1.6:
- Buttons very responsive, including encoder switch
- Some code cleanup