The chain is divided into independent subsections, consisting of:

• MSP430G2231
• 2 input pins detect touch events and receive pulses from its neighbor
• 2 output pins to propagate pulses to its neighbor
• 6 SMD 1206 LEDs
• 100nF decoupling cap (important if you want to avoid brownouts.)
• 100mil / 2,54mm pitch headers
• Coated repair wire for the connections
• R and C for the reset circuit

Programming is straight forward too. The chain can be triggered from the “left” and “right”. So two independent shift registers are used to keep track of the pulses. To output the both registers are XORed and displayed.

Saving resistors and energy is easy. Use the build-in timer with the PWM feature to control brightness of the LED without actually wasting energy. 5 more lines of code and the world is a greener place.

TI’s IDE CodeComposer Studio has two handy tools build in. First is Grace, a graphical configuration engine that allows you to set up I/O’s, Timer, PWM in no time. And at compile time there is the ULP Advisor that checks your code against ULP coding rules to help you minimize energy consumption.