Hi Steve;
I’ve been testing out my new Seeeduino Mega sense it arrived earlier this week. I too was not real clear on the extra I/O pins Vs the Ardunio Mega. What I’ve come to understand is that Arduino mega digital pins 0 to 69 are the same as for the Seeduino and that digital pins 54-69 are the same pins as analog pins 0-15. The extra I/O pins that the Seeeduino Mega brings out are not mapped out with pin aliases in the Arduino core libraries. So the only way to access these additional I/O pins is via direct port access using direction ports and masks to set or reset or read the actual pins. The schematic that Seeeduino published in my other thread on the mega shows the port/bit number of the additional pins.
Bottom line, it’s nice that the Seeeduino folks brought out those additional I/O pins, however the Arduino library does not support those pins directly using the standard digitalwrite/read functions.
At least that is my take on the topic to date.
Lefty