The Pro Trinket 5V uses the Atmega328P chip, which is the same core chip in the Arduino UNO/Duemilanove/Mini/etc. So it's great once you've finished up a prototype on an official Arduino UNO and want to make the project smaller. The Pro Trinket PCB measures only 1.5" x 0.7" x 0.2" (without headers) but packs much of the same capability as an Arduino UNO.
We also added Optiboot support, so you can either program your Pro Trinket over USB or with a FTDI cable just like the Pro Mini and friends. Like the Trinket, it has onboard USB bootloading support - we opted for a MicroUSB jack this time. That's why we designed Pro Trinket, with 18 GPIO, 2 extra analog inputs, 28K of flash, and 2K of RAM. Trinket's a year old now, and while its been great to see tons of tiny projects, sometimes you just need more pins, more FLASH, and more RAM. It's like an Arduino Pro Mini with more pins and USB tossed in, so delicious. The coin cell will have self-discharged decades before the chip would have used it's capacity.Trinket's got a big sister in town - the Pro Trinket 5V! Pro Trinket combines everything you love about Trinket with the familiarity of the common core Arduino chip, the ATmega328. Flash the exact same hex file and sleep current is hovering between 0.1 and 0.2uA. Out comes a $1 Attiny85 and a 10c 0.1uf bypass capacitor. So six months or so in sleep on a 2032 coin cell seems ok? But I've taken an eye from the little fella and I'm not removing it's spleen just to test that! Lets sit at 24uA on a trinket. According to the regulator datasheet, it might sink 3 or 4 more back through it's output. Sure enough, applying the power to the 3V output pin gets another 11uA off. I did say that at these levels, bypassing the regulator is in play. I should be able to get 20 or so from disabling the brownout detector but I believe I'd have to change fuses to be able to do that. Disabling the ADC got me another 0.23 so we're down to 35uA in sleep. Running the sketch without the LED reduced consumption by 3 mA - roughly as expected. I can only assume there are some settings in the IDE compiler configuration that override what the AVR library functions are doing.ĭusted off a few more memories and, amidst much lamentation, removed the power LED from a 3.3V Trinket.
Compiling exactly the same code in the IDE and it still draws a few hundred microAmps. Not sure about the first question but, I have found that if I compile a C PWR_DOWN program outside the Arduino IDE, the result on a bare AVR is sub microAmp. Why does PWR_DOWN still leave the AVRs drawing a few hundred microAmps (deducting LED) in PWR_DOWN? Why are Pro Trinket figures about 0.2mA less than Trinket across the board? In fact, given that nothing is limiting the voltage to the AVR, your consumption will probably go up. Powering via 3V out pin to bypass the regulator is not worth the risk. This example is not particularly demanding. Running consumption will depend on what is running on the AVR. Removing the LED would get to I measured 2.0V drop across the power LED so with the 470ohm resistor you'd save about 2.8mA in all cases by removing it. Note: PWR_DOWN figures for Pro Trinket via 3V output are reversed (transcription error) CurrentDraw.jpg (30.78 KiB) Viewed 2782 times
There could be other minor parasitic drains in the circuitry but those two should get you to your target (he says confidently without being prepared to try them himself.
If you want to mod the pro trinket, you'll need to desolder or cut the trace to the power led, power it via the 5v output BUT make sure you tape over the USB and FTDI ports or you will forget when you flash a program and end up applying two power sources. So this is a perspective rather than a solution. Now I expect pwr_down consumption to be less than a micro amp but I don't expect it on a dev board or via the Arduino IDE. That realisation led me to order a USBTiny programmer and learn about programming AVRs without the Arduino IDE. There're lots of threads chasing low power on these boards, but I searched high and low and there really is no "aha" answer. Heck, I can't even force myself to solder them into projects. I couldn't bear to butcher my trinkets or pro trinkets. If you take off all the pieces that increase consumption on dev boards like regulators, leds, boot loaders, protection diodes etc it's really just a breakout board. Seriously though, while a project lasting a week on battery can certainly be adequate, it's never satisfying when you know it could last for months or even years. Then it's micro amps and before you know it, nothing can fill that burning desire but nano amps. Sure, that's how it starts, you're just trying milliamps.