They say that when calculating time required for a project, you should make your best estimate and double it.
Then add an order of magnitude.
So an hour becomes two days, a week becomes two months, etc.
This adage certainly holds here.
Not much new to mention today, so I’ve included a picture of the prototype controller.
It’s big – 8.12″ x 4.0″. The end user wanted field-replaceable driver chips, so we picked some chunky DIP parts. This board can drive 16 separate strings, and each string can contain 2048 nodes.
The original design had 2 x LM1117 SMD voltage regulators, one each for the +5 and +3v3 rails. But heat dissipation was a problem – nearly 2 W – they were swapped out for a TO-220 package + heat sink. The ethernet controller (Wiznet W5100) is only available in a .3mm pitch, 80-TQFP package. Getting all those leads soldered in only the proper place takes a steady, steady hand.
Rev2 boards are being manufactured right now, and ought to ship on Monday.