Paul has the great fun of trying to be all things to all people,
.
- I use T3.1,3.2 for most projects, and rarely need all of the available I/O pins as it is, although some of my robots do use most of the I/O pins, due to having a lot of sensors and 5V tolerance is good for this. The greatest limitation of T3.1,3.2 for me is the single SPI port.
- I went to T3.6 for my Arducam-Mini vision project, due to speed, amount of RAM (it can hold a couple of image frames), SD card, and multiple SPI ports, so I can more easily interface camera, LCD, and external SPI RAM chips (23LC1024). I will also be using T3.6 on future expansions of my robots, as the current programs are >100K and I will be adding more high-level, abstract kinds of processing that can use the higher clock speeds.
A lot of people seem to like the
smaller 28-pin modules, which is a very convenient size, but also express desire for there being a T3.6 chip on this size pcb. However, I would hate to see the SD card socket go away. So my "favorite" idea would be a T3.6 chip on a 28-pin module form-factor, but expanded to include "2" extra rows of through-hole pads, top and bottom in parallel with the current rows. So, 0.9" tall and 1.5" long. I would remove the end-pads and put an SD card socket there, so it might have to actually be 0.2-0.3" longer. Then, a few leftover I/O pins could go on smt pads on the bottom, like at present, although no one might ever need them.
Too bad for breadboard people, however.