Go Down

Topic: Does the USB Interaface chip waste energy on battery power? (Read 952 times) previous topic - next topic

dkl65

Hello!
I've heard that these components on the Arduino board is most power consuming:
- USB Interface Chip
- 5V voltage regulator
When the Arduino runs on battery power (e.g. 4 AA batteries directly into 5V and GND pins, or 9V battery into DC power jack), is the USB Interface Chip wasting energy? If it is, how can I disable it? I looked at Atmel datasheet, and don't understand all the clk_io abbrevations, and how to manipulate them. Also, what does the USB chip do, anyway?
Thanks!

war_spigot

I'm not really sure.  On the schematic, I see the part that(I think) auto switches between USB/VIN power, but it seems that the Vcc pin on the AtMega8U2 it connected regardless, as it's not powered directly from the USB 5V pin.  I may be missing something though.

Jack Christensen


Hello!
I've heard that these components on the Arduino board is most power consuming:
- USB Interface Chip
- 5V voltage regulator
When the Arduino runs on battery power (e.g. 4 AA batteries directly into 5V and GND pins, or 9V battery into DC power jack), is the USB Interface Chip wasting energy? If it is, how can I disable it? I looked at Atmel datasheet, and don't understand all the clk_io abbrevations, and how to manipulate them. Also, what does the USB chip do, anyway?
Thanks!


I measured an Uno at about 42mA. The ATmega328P accounts for 11-12mA of that. Not sure how the rest breaks down.

4xAA cells is a bit much, absolute maximum voltage for the ATmega328P is 5.5V.

The USB chip (which is just another Atmel microcontroller, specifically an ATmega8U2 or ATmega16U2 on the Uno R3) provides the serial interface between the ATmega328P and the USB connection. This includes uploading sketches via the bootloader.

I'm not aware of any straightforward (or otherwise) way to turn off the ATmega8U2/16U2. I guess it only "wastes energy" if you have no use for what it does ;)
MCP79411/12 RTC ... "One Million Ohms" ATtiny kit ... available at http://www.tindie.com/stores/JChristensen/

retrolefty

Chip wasting energy? If it is, how can I disable it?

Yes, the USB serial converter chip is consuming power straight from the Vcc bus, no matter what the source of this voltage is. Probably around 10-20ma or so, the datasheet for the chip will give better details. No easy way to disable it as it has it's own firmware burned into it and is not simple to write your own version and have some kind of sleep option installed, but it's not impossible I guess.

I looked at Atmel datasheet, and don't understand all the clk_io abbrevations, and how to manipulate them. Also, what does the USB chip do, anyway?

The purpose of the chip is to allow serial communication to the PC via it's USB bus. It's used by the Arduino PC IDE program to upload new sketches and optionally to allow serial communications inside your sketch code to send and receive to a PC application program (or the arduino IDE's serial monitor) if you so desire.

Lefty

floresta

Quote
I guess it only "wastes energy" if you have no use for what it does

Precisely.

The USB chip is used for downloading sketches and for communications with the PC for the serial monitor.  Once you have downloaded your sketch and if you are not using the serial monitor then the power consumed by the USB chip is indeed wasted.

Most modern microprocessor chips have the capability of being put to sleep (but not euthanized) when not in use and it is possible that this is being done in the Arduino implementation.  In that case the wasted power would be insignificant.


Don

Go Up