It is hard to believe, but the V2.2 tree has finally been created - will full color LEDs to boot. For those of you keeping track, it seems to take about 11 years between tree versions.
You can tell the difference pretty easily.
Tree Rev. 01
Our first production tree - in 1997. The base of the tree was a metal holder for two D-Cell batteries with to clips that you slid to make contact and power on the tree. The button was used to change the pattern. This tree used a PIC16C58A microcontroller with a whopping 2K of EEPROM and 73 whole bytes of RAM. There were 32 LEDs (8 each of Red, Yellow, Green and Orange).
As featured in Nuts and Volts in 2008. Two battery clips where mounted on the bottom of the board to hold D-Cell batteries. The processor got a big upgrate to a PIC16F685 which douled the EEPROM to 4K and quadrupled the RAM to a whopping 256 bytes. The LEDs stayed the same on the tree. A new feature of the tree is that the button also allows for turning off the tree by just holding it down.
With 2019 here we created the multi color LED tree with 36 LEDs. If we have to be honest, we ran through a few prototypes in the intervening years until we were happy with the design. With the increased LED count (remember that each of the Multi-Color LEDs has 3 different colors) and memory requirements, the tree uses a PIC32MX250F128B with 128K of EEPROM and 32KB of RAM. Unfortunately the power requirements of the LEDs mean that we could no longer use a pair of D-Cells, but fortunately USB Battery technology has evolved so that you can run the tree off a rechargable battery.