I’m just about studying the feasibility of a device for bikes (a full hub dynamo PWM Led lighting/turning with battery, LCD,bell/horn and various meters/sensors). I’ve found the arduinomega which seems adapted to my I/O needs.
It seems a perfect solution for hobbyist like me, but rather those working on device which are switched when used, or plugged on 220V.
So, I’ve noticed a drawback for my kind of application. My system will be sleeping much on a battery (1Ah), and despite the fact that Atmega have very good low power mode (<1uA, while my limit is ~10uA when sleeping) the USB/TTL interfaces (&OPAmp& regulators) will be eating most of the battery along the year (killing them).
also It might be nice to work below 5V (>2.7v), first to reduce consumption (at the price of clock, and TTL/CMOS compatibility), but also to allow usage of Lithium battery without regulator when sleeping.
This might imply that the 16MHz quartz should be replaceable by a 8MHz
also looking at the schematic I’ve noticed small details, a bit sad.
First, about the TOSC1/2 (PG4/3) which are not connected while it could be useful for a RT 32768Hz quartz. It should even be nice to have a specific connector for that quartz (and the capacitors), as optional.
Finaly according the the schematic, some other pins are not connected at all… a bit sad for a purist (yet acceptable for the basic all-purpose board).
So I suggest to propose an “Extreme” version of the ArduinoMega, without anything mandatory, but all accessible, a bit like the mini version.
It should be designed with the following ideas:
- no IC should consume energy if not needed (by jumpers, by external cards like USB/TTL or Regulator(less expensive), by automatic shutdown below 1uA, a programmable MOSFET switch, a global “power-save” line, low power ICs…). the most simple being to remove all ICs from the main board, even the regulator, letting designer choose their solution…
- 32768Hz quartz should be installable on TOSC1/2 if desired with a DIP
- 16MHz Quartz should be replaceable (or rather proposing a 8MHz, replaceable by 16 or any if needed) with a DIP socket. NB: Maybe a problem with the clock fuse.
- all pin should be accessible, even the less common
my alternative is to buy a TQFP100 PCB adapter (I’m afraid of SMT) or a ZIF TQFP100 connector(price!), and wire my own version (with the bootloader, via ICE programmer).
anyway it is not a demand, not a critic, just an idea/suggestion. I might not be the only one thinking about a long sleeping battery system, RT clock systems, extreme I/O count, and atmega seems good in that. arduino add simplicity to it.
by the way I’ve noticed on Farnell that ATMega2560 is now cheaper that atmega1280… maybe the occasion to please the extremists.