Having spent a lot of time over the last few weeks looking at LPC processors and at first glance I was not impressed by the SAM3U that is being used in the New Ardiuino Due. However I just spent an hour or so quickly going through the SAM3U data sheet and now I think it will be a good peice of kit.
Here is a summary of my first impressions of features that will affect the average Arduino user. Note that I am mostly just looking at the chip, I am not privy to what the Arduino guys are doing or what features they are implementing.
3v3 IO - All IO is 3v3, that's pretty standard for new chips so no surprises there. How will existing shields will work? They probably won't.
Millis rollover - OK this is different but we're always talking about the 49-day rollover of millis, the SAM3U has an RTT (real time timer, that's not an RTC but serves a similar function) that also rolls over and will have to be taken into account by your code.
The 32-bit counter can count up to 2^32 seconds, corresponding to more than 136 years, then roll over to 0.
Just keep that in mind.
Pin current - Forget about hanging most LEDs and all small relays off the pins, source 3mA, sink 6mA, 130mA for entire package.
Timers - at first glance it looked like there are only 3 16-bit timers.
3-Channel 16-bit Timer/Counter (TC) for capture, compare and PWM
WTF I thought? I'm still a but confused but it seems that there are 3 TC blocks and each block has 3 TCs. But 16 bits, again WTF?
However it also seems that within each block TCs can be daisy-chained, so you can have 3 16-bitters, a 32-bit + 16-bit or even a single 48-bit TC. If that's the case then this is a very flexible arrangement giving a total of 9 16-bit TCs or various combinations of 16, 32 and 48-bits.
No DAC - This is a little strange because most modern large chips do, personally I've never had a need for one but there you have it. No DAC.
ADC - There are a total of 16 analogue inputs, same as the Mega but better in that there are two 8-ch ADCs, one is high speed (1Msps) and high(er) res (12-bit), and the other is more like the Mega (10-bit, 384ksps)
SPI - Despite the "5 SPI channels" mooted there is only 1 dedicated SPI port. The other 4 are obtained by using the 4 USARTs. Nothing wrong with that but be aware of the tradoffs.
JTAG - It looks like full JTAG debugging, and from what I can see on the photo the port is connected to a header on the PCB. Maybe I'll finally be able to use my JTAG debugger.
RAM - At 50k this is a little disappointing and not as much as a lot of chips, but a lot better that we've had. Also bear in mind that I'm pretty sure that with this architecture your constants will not be copied into RAM. This will make a big difference.
I2C - There are two ports and it looks like the second one has been brought out to an extended header.
That's it for the time being, I'll delve a bit deeper now, but I'm starting to like this chip.