Monday, July 20, 2009

When 2K is not enough

Good thing I started Wise4Sure as a "pre-prototype" (proof-of-concept). Imagine the frustration of things working weirdly with a prototype board, parts soldered maybe not perfectly, wires over wires, solder bridges and many other potential hardware issues. Then realize that the problems are really in the software, where 2KB of RAM is not enough, due to the SD card library (SHuFAT), which itself uses a half KB buffer to read a sector (see this post).

Based on the newly acquired facts, I decided that the prototype will use an ATmega644, the core of the sanguino. Here are a few technical specs:
  • 4KB static RAM (that's the main reason I chose it);
  • 64KB flash memory;
  • completely through-hole.
Not many stores sell the sanguinos, nor the ATmega644, especially with the bootloader. I ordered mine from

I already started building the board, and one of the first observations is that the distance between the two connectors (2x8-pin) on the back of the 0832 display module from Sure is not multiple of 0.1", as I expected. So my plan to use the connectors as plug-ins the "mother-board" is half ruined. I may need to use only one connector, which would confer less mechanical sturdiness, or have the "mother-board" un-attached mechanically, but connected through the short parallel cable that comes with the display. Both suck.

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