I realize that this is an older thread but I've one related question.
I've got a project that I'm developing on a Due. I chose the Due because it's fast, more and most of the hardware devices I'm using are 3.3v, it has lots of pins and a Chinese board is cheap. Once my development is done I'm thinking that I might want to move to a teensy (I have an unused 3.0) for a demo version. How difficult is the transition going to be? Can I just hook the pins up, change devices in the Arduino software, build and go? How difficult is it to connect to the teensy's inner pins?
It probably would have been better to create a new post, rather than bringing up a post from last year.
Not having programmed the Due, unless you are using Due specific functions or the Arduino style shield layout, it should be fairly easy to transfer from Due to Teensy. It really depends on what you use on the Due.
In terms of connecting the inner pins, if you are handy with a soldering iron, you can just solder wires to the bottom pads to run the connections out. Or there are several boards that make it easier to bring out the connections (some are finished, and others are pcb designs that you can send out to a pcb house to build boards). And if you aren't good at soldering, there are one or two places you can order an assembled board at an extra cost. I've collected several of these over the years, and ordered some, but I haven't actually done the soldering just yet (note, the 3.0, 3.1, and 3.2 differ in where the reset pad is, so if you don't need the ability to restart the Teensy without you can use any of the designs -- note, 3.1/3.2 have more functionality of the underneath pins than the 3.0 did):
Note, I've had 1 or 2 failures with the Teensy 3.0 where the programming button came out. The Teensy 3.2's button is much, much better attached. If your button has separated, you can make a button by connecting the program pin to ground on the 3.0/3.1/3.2/LC.
On the 3.0, the reset pin is on the back pins (reset just restarts the processor, program tells it to send out a request to accept new programming). On the 3.1 it is in a solder pad underneath the Teensy, and the pin on the back became another analog input, and the only analog output pin. On the 3.2, it is also in a solder pad, but in a slightly different location. The other 14 pads underneath are in same location between the 3.0, 3.1, and 3.2. The 4 inner through hole pins and 5 through hole pins on the back are in the same location. Between the 3.0 and 3.1, 6 of the underneath pads gained the ability to be analog inputs, 2 pads gained PWM capability, and a second i2c bus was added.
The 3.1/3.2 pins are mostly 5v tolerant (except for the analog input pins/pads that do not have digital input/outpus, and some of the special pins). The 3.0 is NOT 5v tolerant.
IIRC, the Due numbers its serial devices differently than the Teensy (Due has 0/1 being Serial0 while Teensy has 0/1 being Serial1). On the Due, Serial1/Serial2/Serial3 are on separate pins, while on the Teensy Serial2/Serial3 overlap with digital pins.
Note, the Teensy only has 3 serial UARTs while the Due has 4. Teensy 3.0 has no DAC outputs, 3.1/3.2 has 1 DAC output, while the Due has 2. The CAN bus on 3.1/3.2 (3.0 does not have a CAN bus) overlaps with core digital pins on the Teensy and it doesn't on the Due.