VESC connection problems

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kkolehma
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VESC connection problems

Postby kkolehma » 07 Feb 2017, 22:02

I am experiencing frustrating problems connecting to my VESCs, I have three of them one from exertion version 4.10 and two version 4.12's. I was previously able to use ll them no problems at all, but things have gone for the worse since then.

Until while ago the situation was that I was only able to connect one of them (one of the 4.12's) with USB to PC. The other two boot alright (blue led and three red flashes, then blue and green on) but no USB connectivity what so ever. I have custom PCB and I was originally using VESC's via USB, which worked fine until I updated the PCB and in my opinion improved the USB routing ( I only connect D+ and D- as both electronics and the VESC are supplied with same battery). But only one of the VESC ( I use two) enumerated in my embedded linux device. Problem turned out to be bad soldering on the the USB connectors on the Linux device. Then I could no longer connect the other 4.12 to the computer either. Same thing with the older 4.10 board.

Well I thought that UART might be more forgiving in terms of shady signal routing. None of the ESC of course didn't work via UART as the application is not set to UART.

SO I went on and connected the only VESC I now could connect to computer and used BLDC tool to configure it to use UART + ADC. It was the only setting I changed. I plug off the VESC from power before disconnecting and put in my device and connect Rx and Tx cables and nothing happens....

Well I notice that none of the LEDs in this VESC that should be able to talk via UART are on. The I plug it my lab power and see that now it drains 250 milli amps at 15V when it used to take 40 or so...

So the question is that WTF should I try now? The two non connecting ESCs I would like to resuscitate if i knew how, and I sincerely would like to know why this one ESC suddenly without any good reason seems like short circuited. Flashing the two might be one option to try if those freeking STM prommers would work ( I have two of those chinese copies) but they only work in Windows (as far as I can tell) and I haven't been able to get the do anything with any board I have tried to use them on...

I feel stupid now since the problem must be obvious stupid thing that I have overlooked. I just hope I haven't ruined all of those three VESCs... Have to try and continue tomorrow to debug these things...

rew
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Re: VESC connection problems

Postby rew » 08 Feb 2017, 10:32


kkolehma
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Joined: 26 Dec 2015, 15:37
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Re: VESC connection problems

Postby kkolehma » 10 Feb 2017, 13:23

Thanks, that is probably a good idea to keep GND connected. I'd imagine same goes for UART. I just pray that I haven't completely screwed up the ESCs as they don't enumerate on my computer either anymore though based on LED's they boot up OK. Apart from that one that developed some issue with power management side...

kkolehma
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Joined: 26 Dec 2015, 15:37
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Re: VESC connection problems

Postby kkolehma » 10 Feb 2017, 16:45

Little update on the problem. The two VESC's that do boot (according to LEDs) give usb error -71 on my Linux laptop (and thats the 4.10 version). The other 4.12 which do boot, doesn't cause any life on Linux and the one drawing crazy current is not responding either. So each of them fail in unique way.... -71 I suppose means protocol error, but that can be due to any number of reasons. I did try with more than one cable with no change in the outcome or the error.

kkolehma
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Re: VESC connection problems

Postby kkolehma » 10 Feb 2017, 18:57

Ok so the VESC that is drawing too much amps is indeed short circuited somewhere. I can't find any obvious reason and as I said it was working fine before plunging it off from computer. I took CAN adapter and associated capacitors away in case the CAN adapter was faulty for some reason and I don't intent to use it anyway. Still 0 ohms between GND and VCC. So went on and took of the LDO incase it was busted, but still 0 ohms. I think only possibility is that STM is physically broken.... There is not many other 3.3V devices to take off...

Well then the two others. I put jumpers on so that they can be powered from USB. Things changed in the way that the red LED keeps on blinking after boot, no other change.... Curious thing is also that VESCs draw good deal of more amps from power source if USB voltage line is up... What could be the reason for that?

rew
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Re: VESC connection problems

Postby rew » 11 Feb 2017, 08:39

Mine do that too.... (and I have a non-VESC project on my desk now that does it as well!).

The reason is that the VESC (and my other project) make a 5V from the "motor voltage". When you connect the 5V on the USB, your project will backfeed 5V into the USB hub or the computer.

Resistances in USB cables prevent your VESC from trying to power the whole 5V rail in your computer (maybe 20A!).

pf26
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Re: VESC connection problems

Postby pf26 » 11 Feb 2017, 16:38

@ kkolehma: when you want to locate where a short circuit is present on a pcb, you can use a current limited power supply (say around 100mAmps) to supply the board. Then try to see where the voltage drops occur along the pcb tracks. Because the little pcb track are sligthly resistive, they will show a little amount of voltage when they are in the current path to the short circuit. Tracks that are not circulated with current will show 0 millivolts.
You can also locate short circuit from the heat (especially if you have thermal imaging).

rew
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Re: VESC connection problems

Postby rew » 11 Feb 2017, 23:15

Oh, I voltage-limit to preferably 0.5V, but if necessary up to the nominal voltage of the shorted rails.

Then I use up to 2A of current to find the short. You'll have a voltage drop over each wire that is carrying current. You'll easily be able to follow the current through your board this way.

kkolehma
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Re: VESC connection problems

Postby kkolehma » 12 Feb 2017, 12:51

Thanks for the good ideas.

I tried to measure the 3.3V pads with lab power set to 0.5V and I was able to read 0.3or so from all of the exposed VCC pads. I increased the voltage to 1V and measures voltage on pads was 0.5-0.6V range. Also the STM32 heated up quite abit which leads me to believe that it was somehow damaged when I unplugged the power from board, perhaps via DRV8302 as it also connecting to VCC. I doubt that voltage spike via LDO could have busted the circuit as there are quite a few capacitors between LDO and STM. REF pin from DRV8032 is directly connected to STM32 and it also sees se full supply voltage (in this case it was 15V).

I think this ESC is lost cause. Especially since the solder they have used on this seem to require a lot of heat to reflow, I don't think I am going to try to replace the STM...

kkolehma
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Joined: 26 Dec 2015, 15:37
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Re: VESC connection problems

Postby kkolehma » 12 Feb 2017, 14:20



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