Spent some time to figure this out and thought I would share a solution.
The Mega 2560 shield is a pretty good fit to a Due and others have reported it works well. These are cheap and can be bought assembled for a few dollars. I haven't seen a purpose designed version for the Due (does anyone know one??) so I thought to use one of these.
Problem. I have kids using my arduino Due. My 8 YO son has the nickname Destructo- Boy. You can guess his not so secret super power ......
There are dire warnings that +5V on any pin will destroy the Due and as delivered, this shield bristles with many such +5V pins 0.1 inches from sensitive little due pins..... disaster waiting to happen.
A second problem is that the Due +5V can only supply 180mA while the 3V3 is 800mA. Using the +5V on many sensor pins may exceed 180mA.
So a solution is to take off the jumper (PWR_SEL) and feed 3V3 into VCC of the blue terminal block. Problem sorted? Not quite. The 16 analog pins remain at +5V!!!
After some investigation I came up with a mod as a solution.
WARNING: YOUR BOARD MAY NOT BE THE SAME AS MY BOARD AND THIS MOD MAY DESTROY YOUR DUE IF YOU ARE NOT CAREFUL.
Please see the attached picture of the mod.
Once you do this all of the V pins will be at 3V3. If you want them all back at 5V, then remove the red wire and replace the PWR_SEL jumper.
There are still a few 5V Pins on the Bluetooth, URF01, APC220, ICSP and SDCard connectors for use with 5V devices and can be used for devices that need 5V. Should pose an acceptable risk between utility and danger.
A word of warning. Not all the shields have the same layout. On one shield I had to cut a second track due to connection to the second 5V pin on the double header being connected.
Thus I recommend:
- Cut the track after the bluetooth +5V and before the analog V pins as shown. Bridge the analog V pins to the digital V pins as shown. DO NOT ADD THE RED WIRE YET!!!
- Remove the PWR_SEL Jumper.
- Plug in the board (with no other connections) and measure the V pins with a multimeter. They should be at 0V. If they are at 5V then you have another track to cut- most likely from the 5V pin on the double header. Find and cut that, then test for 0V again. WARNING: IF YOU CONNECT THE RED WIRE WHILE THE V PINS ARE AT 5V YOUR PROCESSOR OR OTHER COMPONENTS MAY FRY!!!!
- Add the red wire and test that the V pins are now at a lovely safe 3V3.
As a purist, it is not really ideal to have the analog and digital 3V3 from the same source but separate 3V3 does not seem possible for the Due and even the Mega shield does not do this properly anyway.
It may be wise to add a decoupling cap or two and a small resistor (say 10R) to bridge between the digital and analog 3V3 where my wire bridge is. I'll do that if I have noisy A/D readings.
So happy tinkering!
If your board requires a different treatment or you have a better solution then please add to this post.
