1: The Seeeduino Mega has 16 extra digi i/o pins, but these pins are difficult to use, and surely won’t be supported by the stantard Firmata sketch (which isn’t functional for the normal Arduino Mega, anyhow, according to info on the Arduino forum).
Note familure with Firmata, but the 16 extra digital pins are not really difficult to use, just that you can’t use the built in Arduino pin numbering when doing digital reads, digital writes, and pinMode those extra pins. You have to utilize direct port statements as shown in my example above.
2: These extra 16 digi i/o’s cannot be used simultaneously with the 16 analog pins that they share traces/microcontroller pins with. Or can they?
Not True, the extra 16 digital pins are just digital pins. The sixteen analog pins, A0 to A15 are ALSO avalible as digital I/O pins by referencing them as digital pins 54 to 69. These analog/digital pins can be used with the standard Arduino digital pin commands as either analog using pin numbers 0-15 or digital using pin numbers 54-69 by either the Arduino or Seeeduino mega boards.
3: The standard Arduino Mega may be able to do the same thing as the Seeeduino Mega and produce 16 more usable digital i/o’s; it would just require a firmware revision and some extra off-board wiring? Or is there more work which would have to be done to access these pins?
Those pins are not avalible on the Arduino Mega because they didn’t run printed circuit board traces from the Mega1280 chip to any connector, they are just left unconnected on the Arduino Mega, so physically unavalible on the Arduino Mega for hardware reasons, no firmware or software changes can fix that. IF the Arduino mega had run the extra 16 traces AND they had updated the pin mapping software, those 16 ‘extra’ pins would be nameed pins 70 to 85. But they didn’t so those 16 can only be accessed by using direct port statements in oyur sketch.
Or is this completely impossible on the original Mega?
Yes, impossible.
The way the posts above are worded, it seems the analog pins 0-15 share circuit board traces with the digital pins 54-69.
Yes, A0-A15 and digtal pins 54 to 69 are the same physicall I/O pins on the processor. But these are NOT the same as the ‘extra’ 16 digital I/O pins that the Seeeduino Mega wired up.
which means that those digital pins are just duplicates, as you would get from stacked headers sprouting off of a shield on an Arduino. This theory would further confirm my suspicion that you can’t use the extra 16 digital pins at the same time as the analog pins.
No you are confusing different pins. We are actualy talking about 32 different I/O pins, 16 are digital only pins that only the Seeeduino has wired out to connectors that the Arduino software can’t utilize via standard Arduino pins commands, but can be acessed via direct port statements. The 16 analog pins can be utilized as digital pins by either the Arduino or Seeeduino meaga boards by using shotware pin numbers 54 to 69.
So anyhow, could someone with experience confirm or deny any of this? I really want to purchase a Seeeduino to base a prototype of a production piece off of, but I can’t until I have this stuff figured out.
Bottom line on I/O pins, the AVR mega1280 processor has 70 total I/O pins avalible. The Arduino mega only wired up 54 of these pins, 38 digital only and 16 analog/digital pins. The Seeeduino mega wired all 70 I/O pins, so there are 54 digital only pins and 16 analog/digital pins.
I like the Seeduino design and extra features better then the standard Arduino Mega, but that’s just my opinion.
Lefty