Author Topic: Measuring power consumption while connected usb  (Read 1159 times)

rocsta

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Measuring power consumption while connected usb
« on: February 12, 2016, 04:11:36 AM »
Dear all,

sorry for the prerhaps stupid question:
Is it possible to measure the power consumption of my project while the Moteino is connected for testing purposes (I would like to see the debugging output) with usb (FTDI Controller)?

I don't think so, but perhaps someone has an idea.

Kind regards,

rocsta

TomWS

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Re: Measuring power consumption while connected usb
« Reply #1 on: February 12, 2016, 07:40:13 AM »
Dear all,

sorry for the prerhaps stupid question:
Is it possible to measure the power consumption of my project while the Moteino is connected for testing purposes (I would like to see the debugging output) with usb (FTDI Controller)?

I don't think so, but perhaps someone has an idea.

Kind regards,

rocsta
It depends...  How is your Mote powered (if from the FTDI cable then it will be hard to measure)?

Can you put your mote in modes in which the debug interface is quiet (not txing messages)?

If you are powered from another source AND you can disable the debug outputs while testing power consumption then you can get SOME accurate measures of power consumption.  The trick, if you're sleeping the processor, is to do a Serial.flush() prior to sleeping.  I also do this on return from sleep as well, but it's probably not necessary.  If you don't flush() then there will be garbage in the TX & RX buffers when you return from sleep.

I say SOME accurate measures because you need to be very careful when measuring very low power consumption (<10uA) and I wouldn't try to get these kinds of readings with a debug cable attached.

Tom


rocsta

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Re: Measuring power consumption while connected usb
« Reply #2 on: February 12, 2016, 11:30:10 AM »
>>It depends...  How is your Mote powered (if from the FTDI cable then it will be hard to measure)?

It can be / it is powered with a separate power supply.

>>Can you put your mote in modes in which the debug interface is quiet (not txing messages)?

After send to sleep, no more text messages will appear

>>If you are powered from another source AND you can disable the debug outputs while testing power consumption then you can get SOME accurate measures of power consumption. 

That's nice, but how ?  ;D

>> The trick, if you're sleeping the processor, is to do a Serial.flush() prior to sleeping.  I also do this on return from sleep as well, but it's probably not necessary. 

Yes, I do this.

>> I say SOME accurate measures because you need to be very careful when measuring very low power consumption (<10uA) and I wouldn't try to get these kinds of readings with a debug cable attached.

Of course SOME. During testing the different code it's stupid to go on as follows:
1 Implement (I use now ATMEL Studio 7 with Visual Micro AddOn - very nice ... - much better than Arduino interface)
2 Upload new Software
3 Unplug ftdi
4 restart mote
5 stare on LED, until it goes sleeping (BLINKBLINK  :D )
6 check consumption
7 plug ftdi
GOTO 1

 :)

TomWS

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Re: Measuring power consumption while connected usb
« Reply #3 on: February 12, 2016, 12:14:44 PM »
#6 should be ok to test power consumption.

Tom