[Tinyos-help] Ultra-Low power

Eric Decker cire831 at gmail.com
Wed Dec 4 11:40:18 PST 2013


Possibly the FTDI chip.   But I doubt it.   Looks to me like the FT232BM
(the FTDI chip) is powered only when plugged into a USB port.


Also the Radio doesn't really power all the way down.   When in the Driver
state PD, the Radio has XOSC turned off but never really turns off VREG_EN
to power the chip all the way down.  It isn't much.  20uA XOSC off/VREG_EN
on vs.   1uA with VREN_EN off.   Given that you are talking about 10s of uA
that you'd like to be gone, the above is significant.


How are you actually measuring power consumption?   Where in the circuit?


On Wed, Dec 4, 2013 at 3:17 AM, Bdiri Sadok <bdiri.sadok at gmail.com> wrote:

> Hello,
>
> I'm working on ultra low power system design. I'm using Telos Rev. B as a
> research platforms.
>

First the telosB is not really a good candidate for ultra low power system
research.   It is a very old design.  The more modern chips like the 5438a
are much better at this.   Low power is one of the reasons TI went to 1.8V.
  That is why we also went to the 5438a and run most of our system at 1.8V.


> While developing, i was trying to put the mote in its lowest power mode. I
> believe the MSP430 should go to LPM 4. I've done that.
>

Be aware that the TI MCUs have bypass mechanisms that prevent certain
pieces of say the clocking system from shutting down depending on how the
peripherals are programmed.   So it may look like something is powered off
but isn't and TI doesn't provide a mechanism for checking say a status bit
so you can go look.

You have to carefully read the user's manual as well as the particular data
sheet for the mcu in question.


The mote still consumes about tens of µA which has to be around hundreds of
> nA. I'm suspecting the FTDI chip since it's not powered through the MCU
> which make its power mode (if there were any) uncontrollable.
>

Shouldn't even be powered if the USB isn't plugged in.

I am assuming you have a schematic, yes?


> I don't know if some of you have tried that. So if this's true i'll just
> disconnect the power line that goes to FTDI chip and control it using a
> mosfet transistor connected to MCU.
>
> Any hints will be apreciated.
> Sadok Bdiri
>
>
>
> Research Assistant in HTWK Leipzig, Germany
>
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>
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-- 
Eric B. Decker
Senior (over 50 :-) Researcher
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