TDoA anchors losing power

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sali0
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Joined: Wed Oct 19, 2016 7:53 pm

TDoA anchors losing power

Post by sali0 » Thu Feb 16, 2017 10:25 pm

Hello all,
My team and I recently got our TDoA set up, however we are running into a few issues. We had tested extensively with the ToA configuration, and we got our system running properly. However, after flashing to TDoA, when turning all of the anchors on, the anchors start communicating but soon turn off randomly, about 1 minute after starting all of them up. We have all 8 anchors up, but are unsure of what is going on with the power.

Seeing as the Bitcraze team has gotten TDoA working properly, our probable issues are from what we can tell either the power banks that we have, or some issue with the clock syncing in the TDoA code. I am leaning towards the second issue, as there were no power issues during ToA, but I still do not know. I will also try to get some recording of what is going on. Any help is appreciated. Thank you.

NateTheAverage
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Joined: Thu Sep 29, 2016 10:40 am

Re: TDoA anchors losing power

Post by NateTheAverage » Sat Feb 18, 2017 12:40 am

Sorry its not any help but I have TDoA set, with the current firmware flashed and get 6 hours out of 2,000 mh batteries. I haven't ran in to any issue turning off anchors.

arnaud
Bitcraze
Posts: 1218
Joined: Tue Feb 06, 2007 12:36 pm

Re: TDoA anchors losing power

Post by arnaud » Mon Feb 20, 2017 3:20 pm

Hi, this is actually very likely to be a problem with your USB power pack, we have seen the same behavior with some of ours.

The problem is that the TDoA mode does not consume enough power(!), the usb power bank will think that whatever connected to it is charged or disconnected and will switch itself off. The reason why TDoA does consume less than TWR (ToA) is because the TWR anchors are always listening and so cumsume more than 100mA continiously. The TDoA anchor are synchronized together and only listen/send during timeslots, this reduces greatly the power consumption.

I have usually fixed the problem by connecting 2 anchors per power bank, this way the power consumption is enough to keep it on. We also have a different kind of powerbank (smaller one, like 2000mAh) that are good for 1 anchor.

sali0
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Joined: Wed Oct 19, 2016 7:53 pm

Re: TDoA anchors losing power

Post by sali0 » Mon Feb 20, 2017 7:08 pm

I am happy we weren't the only ones to see this issue. I have though that maybe attaching a moderately large resistor to draw more power may work. Could be attached from the cathode of D9 to the ground of C1. I looked on the documentation of our power banks and it does not state what draw it needs to remain on, so I guess trying a few resistors may not be a horrible idea.

edit: another solution could be to short the cathode of d11 to terminal 2 of P4. That way we could test resistors by inserting them in p4 without soldering and desoldering them.

arnaud
Bitcraze
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Joined: Tue Feb 06, 2007 12:36 pm

Re: TDoA anchors losing power

Post by arnaud » Tue Feb 21, 2017 9:44 am

If you want to mount a resistor, I would suggest connecting it to the P5 connector instead, there you can access VCC and GND and you will not have to deal with the SMD components. Be careful to not short the power supply or to put a too low resistor.

I would not recommend hardware hack, it would be nicer to have a software fix for that. For instance lighting up all the CPU LEDs might make a difference, they consume 10mA each so you will increase the power consumption by 30mA by switching all of them ON. The radio algorithm could also be modified to switch ON the radio more often to increase the power consumption (this is something we are planning to do eventually to implement a "management" channel to be able to send packet to the anchors).

On a side note, it is the first time I look around a datasheet trying to find way to make the radio consume more power :-).

sali0
Beginner
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Joined: Wed Oct 19, 2016 7:53 pm

Re: TDoA anchors losing power

Post by sali0 » Sun Feb 26, 2017 5:35 pm

Just a quick update.

We got the anchors working with our power packs. We decided on a 180 ohm resistor on P5 as Arnaud suggested, only pulling enough current to keep the power pack on. I do not foresee any issues with this, but the resistor will be removed if there are changes to the power consumption of the anchors which leads it to not be needed. For now, this solves our issue and allows us to further test. Thank you for the help.

arnaud
Bitcraze
Posts: 1218
Joined: Tue Feb 06, 2007 12:36 pm

Re: TDoA anchors losing power

Post by arnaud » Mon Feb 27, 2017 2:41 pm

Thanks for reporting your success, it is good to know that this was enough to keep the USB battery ON.

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