I've been looking for an excuse to do something with the LPC1347 for a while, and I ended up recycling a lot of previous work, combining a number of lessons learned into a single four-layer board that should let me test a number of power supply and project scenarios. I kept the board fairly basic, just a microSD card for datalogging, USB, and SWD connector, and reset/ISP buttons. There's on on-board user-selectable 3.3V/2.2V linear regulator (TPS780), but it can be bypassed and you can power the board from another source for flexible power input and current control. It's designed to fit in these inexpensive weather-proof cases
with a transparent top for a small solar cell, but should be easy to adapt to another enclosure.
I kept the RF section completely seperate as well so that I can change to another chip if required. The current board uses an AT86RF212 (868/915MHz 802.15.4), and I can drop in an AT86RF230/231 (2.4GHz) with a simple adjustment to the transmission line width for impedance matching ... but I also whipped up a schematic for the nRF8001 for Bluetooth LE that I might test down the road. The way the board is now I can make seperate 2-layer add-on PCBs for various power and sensor inputs, sticking to one common footprint and header to evaluate things more quickly.
One benefit of the ARM Cortex M3 based LPC1347 is that it's pin compatible with the Cortex M0 LPC11U24 and Cortex M0 LPC11U37. This gives me a decent selection of options between price/performance/flash size on a single PCB, with minimal SW changes, all of which have excellent power numbers:
- the LPC11U24 is dirt-cheap - 50MHz M0, 32kB flash, 8kB SRAM
- the LPC11U37 has lots of flash for complex stacks - 50MHz M0, 128kB Flash, 8+2+2kB SRAM
- the LPC1347 is a high-performance chip with a decent amount of flash - 72MHz M3, 64kB Flash, 8+2+2kB SRAM and 12-bit ADC
It's just a personal, weekend project, but I'll blog some more about this board when I get the PCBs in later this week since it was a big (if expensive) learning experience. Here's some photos of the PCB being manufactured, though, if you've never seen the different steps of the process (courtesy PCB Pool):