Which microcontroller?

When I began this project, I was long given up on the ATMega and ATTtiny micro, with some exceptions, as they are not really justified in a hobby environment. Therefore, I have initially intended to make my nodes using an ATXMEGA32E5, which I believe is an ideal device for sensor nodes, due to the various and low power peripherals. However, it soon turned out that for some devices I would need more flash, but the family stops at 32K and a package change is required for more memory. So I dropped it in favour of the new SAMD21, ARM cortex M0, which comes with more flexible package and flash options. This device burns a little bit more in sleep, but still tolerable. And a 128K flash and 16K RAM version costs on par with the lousy old atmega328 with tons of extra features (way better ADC, DAC, more PWM, more timers, more I/O, more flash, more RAM, faster core, lower uA/MHz, RTC, more SPI, mor UART, more I2C….i’ll stop here).

More info at http://www.electrobob.com/1000-1000-hardware/