This lab builds on Lab 4 to make a device that flashes an RGB LED in an interesting pattern in a way that depends on the ambient temperature. The goal is for you to continue to master combining multiple elements of embedded system architecture.
thermodot.c file (Canvas)Begin by assembling your mood ring PCB and programming it with the code you developed for Lab 3. PAY ATTENTION to the values of resistance you use with the RGB LED. If you make them too big, it may be fine when running from USB power, but cause problems when running from the battery.
Unlike Lab 5, in this lab, the colors for your Thermodot should range throughout the color spectrum including red, green, and blue and shades in between. Bright red should correspond to hot and bright blue should be cold. For inspiration about the colors in between you can look at the wikipedia page on color temperature (though note that for us, hot and cold are reversed from black body radiation).
Specific Requirements It is not enough to just vary the PWM levels as many of you did for Lab 5. Different colors have different perceptual brightnesses, and many of you also noted that the perceptual variation in brightness from 0 to 50% duty cycle is much larger than 50% to 100%. The point of this exercise is to recognize that when you see an LED-based UI, thought has gone into choosing the drive levels to achieve colors which are mixtures of the primary LEDs to account for differing brightness and different __perceptual__ brightnesses (e.g., of green. You will be graded on whether your colors go through a perceptually-nice rainbow. Be prepared to modify your code to sweep through the possible range of temperatures automatically for visualization purposes. You must demo your actual device working from battery power. Note that this will mean different currents flowing through the LED than when driven from USB power!
Your code should be well commented and modular!
Save your firmware as thermodot.c. Turn this in on Canvas and demo your
device to the lab staff.