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ST² Program History

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Thermal Probe Home

Version 0.1 - test01.bs2 24 October 2001

• Simple unfinished program.
• Obtains temperature from parallel ADC.
• Checks the position of the heat selection switch every loop of the program.
• Blinking LED skeleton.

Version 0.2 - test02.bs2 25 October 2001

• Device supplies power to heating element and displays lights depending upon thermistor/ADC input.

Version 0.3 - test03.bs2 26 October 2001

• Blinks the green LED when the temperature is lower than the minimum acceptable temperature.
• Checks the thermistor circuit upon startup. Device fails if the temperature does not rise a certain amount in a specified amount of time.
• Upon device failure, the heating stops and the red LED blinks. The device has to be restarted to exit the failure mode.

Version 0.4 - test04.bs2 1 November 2001

• Added basic timing function for individual skin sensitivity tests (i.e. the five-second timer).
• LED check upon start-up.
• Bug fixes for thermistor circuit check subroutine.

Version 0.5 - test05.bs2 2 November 2001

• Changed to a serial ADC input.
• Checks for a temperature change that is too fast. Any time during operation, if the temperature rises too fast (or saturates positive), then the device will fail. Similarly, if the temperature has a significant drop within one clock-cycle then the device will fail.

Version 0.6 - test06.bs2 9 November 2001

• Uses old calibration data for probe target temperatures.
• Added five-minute auto-off function. The device will stop heating and displaying lights when the probe has not been applied to the subject's skin for five minutes.
• Implements timing switch as a skin switch. The five-second warning timer runs only when applied to the skin. The timer will reset and the buzzer/yellow LED notification will stop when the switch is released.
• Added code comments.
• First testing performed with analog circuitry and heating element.

Version 0.7 - test07.bs2 19 November 2001

• The program stores a failure code after a suspected circuit failure. This code will be displayed as a series of flashing LEDs upon device startup.
• After a failure, the device will not operate until a reset button is pushed. Even restarting the device will not reset the failure status.
• Extra variables were removed from the code.

Version 0.7.1 - test071.bs2 19 November 2001

• Pins were reassigned.

Version 1.0 - st2v10.bs2 7 December 2001

• Pins were reassigned for circuit board layout reasons.
• Program checks reset button. If depressed upon program startup, the program will reset the error code to 0 but still continue to the program failure loop. This is in case the reset button is shorted.

Version 1.1 - st2v11.bs2 19 April 2002

• Used calibrated data for the new thermal probe.
• Implemented threshold control of heating. Upon reaching a temperature threshold, the duty cycle of the heating element will reduce to prevent overshooting the target temperature.
• The heating duty cycle for the thermal probe is increased if the skin timer switch is depressed.
• Failsafes were temporarily removed.

Version 1.2 - st2v12.bs2 9 May 2002

• Reinstated failsafes.
• Added two more error checks. The device now fails if the thermistor value approaches low saturation, or if it rises greatly above the hot target temperature.
• Added several calls to the temperature reading subroutine upon startup to clear initial spurious values seen from the ADC. This helped reduce the occurance of false errors.
• Added a time delay between the sensing of the error and the actual writing of the error code to EEPROM. This eliminated a source of error when the device was simply switched off. Instating a delay meant that errors during operation would be caught and flagged while "errors" on shutdown would be caught but not flagged.
• Balanced the time for each path through the code when the skin switch is depressed for accurate timing.

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