I am always searching for smaller, cheaper microcontrollers! Especially with UART.

NEC makes some compelling devices because of package size (2x2mm), but their feature set is very limited. No UART, no comparator.

Microchip doesn’t put the debug engine on their smaller, lower-cost micros. If you don’t mind debugging on a different micro, their F687, in 4x4mm QFN, is an attractive target for some designs, about a buck fifty in small qtys. Of course, they also make some very tiny, very low cost devices (10Fxx), but they are just too awful to program.

Zilog makes some 5x6QFN parts with UART, and they have a free dev environment. Hardware multiply! Lots of memory. About a buck and a half in small qtys.

NXP also make some small footprint and low cost (about a buck) micros, but only 1k mem max. Still, if you can make that work, the price is a powerful argument. High speed architecture, nice UART features, 3x3QFN.

Silicon Labs makes some useful micros for designs requiring lots of power and small footprints. Hardware multiplier, big memory options, fast clock, 3x3QFN, starting at about a buck seventy-five in small qtys. Can migrate to an OTP part for higher volumes, which cuts the price about in half.

Atmel makes one small, low-cost micro with UART, but it is too memory-constrained for many of my designs. Still, cheap.

As the creator of the MSP430 user group, I feel compelled to mention TI‘s offerings. 6x6QFN, just over two bucks in small qtys. Buckets of memory, extremely low power, hardware multiplier.

And honorable mention goes to Freescale‘s RS08 family, very few peripherals, not C programmable, but less than fifty cents even in small qtys.

Let’s make tiny smart objects!