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ChuwiHI13 and the Keyu battery charger

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szucsi|Post time:10-17-2017 06:17:32 View:3784|Reply:79

MemberChuwi| Post time 10-13-2017 11:25:32 | Show all posts
Does not charge... behaves like I tried to charge with 5V and the supplied adapter cable... hope it is the cable.  

Need to get another one asap.

USB-C otg still works fine.
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artowi| Post time 10-13-2017 11:32:59 | Show all posts
The USB-C connector needs to go in quite deep.  I trimmed a little of the molded PVC on the plug on one end of the cable (less than 1mm) and now it can fit well.  Maybe you don't get a connection on CC1/CC2 so the power negotiation doesn't work.  
Also possible that you don't have a fully connected USB-C cable with the wires for CC1/CC2  missing

All experiments with the Aukey should be rather safe.   Working OTG is good sign.   My profile picture in full shows you the hot area if chip was burned (FLIR thermal camera).
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MemberChuwi| Post time 10-13-2017 11:53:08 | Show all posts
The plug seems to be hard plastic, not sure what happens if I try to cut there... it's a RawPower charging and data cable, nothing special I guess. Some on amazon think it is USB 2 only...

The Otg Cable is Aukey, seems to fit better. I've checked a USB 2 flashdrive and a USB 3 HD. Both apparently work, so Hi13 delivers power on request.

Which cable is known to work? There are so many cables... sigh.
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MemberChuwi| Post time 10-13-2017 11:57:02 | Show all posts
Maybe an Apple USB-C cable fits?

I want to make sure the port is ok and the Aukey charges proper. There is still time left to return the tablet to amazon in case...
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MemberChuwi| Post time 10-13-2017 13:49:32 | Show all posts
Edited by MemberChuwi at 10-13-2017 14:36

I've looked into the video I referred to again and have to say I see no problem with the pullup of 47k up to 12V you stated.

The pulldown is 5k1 so you get a division roghly of 1:10 or something like 1.2V at cc pins, not 5V and not 12V. That seems not to be an issue if 6V is the max. input voltage spec for cc pins. If I got the video right the voltage determins the current limit request by the consumer right? Referring to the table of pullups and assuming 5V the resulting Voltage equals approximately a voltage the 47k pullup @12V provides, indicating about 2A... so it may be a hack but cc input voltage looks nor dangerous neither out of spec... maybe I do miss something here?

The configurarion line has it's own supply voltage, Vconn, but thats provided by the tablet, not the power brick. I don't think Vconn is retrieved directly with some magic from Vbus but just the normal 5V the board uses anyways, which is created from the charging logic, isn't it? There might be some current up to 12V of about 0.15mA via the pullup dissipating about 1mW, can't see a serious threat or overload here as well.

Remains the permanent 12V issue, the boot idea and the plugs.
The 12V is not PD compatible and will destroy other devices. That's a point I agree to 100%.

But the Chuwi can not charge with lower voltages and if Vbus circumvents the USB-C chip as you assumed this is no issue for the Chuwi either. I can't see any need to use Vbus anywhere else than with the charging circuitry. The Battery does also not provide 5V, there is another transformation necessary... I also guess that the tablet does no provide charging other USB-C devices with Vbus > 5V.

We don't know wether the boot bug is real. If it is, it is a problem with the permanent 12V, but that should fry the charging logic. Is this in the same chip?

When I look on my personal experience with the charging cables plug not fitting snug I've just tried with the Aukey charger I still believe the plugs are the main issue here.

Probably we can find out more? Have you more detailed data like the pullup resistor value to do some more simple stupid math...? ;)

Please don't feel offended, I'm just about the facts. Let's put our heads together and gather as much ideas and information as possible! I want to find out where I'm wrong as well.

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artowi| Post time 10-13-2017 15:04:15 | Show all posts
I agree that it is unlikely for the damage to be caused by a current delivered thru a resistor with many kiloohms.   
The 5k1 pulldown the Hi13 side is not active always but only if the N-Ch mosfet connected to PD-enable is active?  The voltage range on the CCx pins should be always  0-5V and I think pulling towards +12V is nothing that should be done ever.  The CCx should have protection against static discharge and a current of less than 1mA will never ever burn anything.  

The resistor value is 56k but it should pull up to +5 instead of +12.

I think we both agree that hard wiring +12V to VBUS is not ok and plugging a hard wired 12V USB-C may kill other devices - right ?

Most plausible theory is a bad plug/socket connection feeding VBUS +12V to the CC1/CC2 lines of the PD controller.  

Without knowing the functional details of the EJ898A we will not know if it is possible to force the VBUS output driver to switch on the VBUS output Mosfet.  

We don't know if the EJ898A can measuer the true VBUS voltage with AD converter or if it just assumes the voltage to be 5V since no other negotiation was completed successfully.  If the EJ898A assumes 5V present on VBUS switching on the output driver will be fatal...

The Hi13  seems to be a valid and well done USB PD compliant design so if connected to PD compliant charger I don't see any risk.

At the moment it seems the CHUWI will not keep the promise given to me about replacing the mainboard.  The options are buying another mainboard at full cost or removing the the dead body of the EJ898A chip to reduce power consumption and using the KEYU charger to charge. Both not really thrilling.
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MemberChuwi| Post time 10-13-2017 15:47:17 | Show all posts
Edited by MemberChuwi at 10-13-2017 21:11

I agree that the Chuwi charger design is not PD compliant and can destroy other PD compliant devices. That's clear now.

It's also obvious that the plug is an issue. The deep connector is also a problem because it's difficult to find cables with plugs that fit snug. This problem returns with any accessory one might wish to connect. Maybe it's not dangerous as long as anything remains at 5V...

I agree that the pullup design is a hack - sure. Again the pulldown is on the tablet side. Don't know if pulldown can be disconnected. This would be another hazard then.

I fully understand your frustration. Why do you think do I take the massive effort to understand the issue... I want to avoid to experience what you faced with your device.

BTW 1, how much is a new mainboard? Does Chuwi ship this at all?

BTW 2, the micro hdmi connector looks badly moulded, frustration 2 around the corner, I most likely expect the adapter I've laying around not to fit properly, mechanically... but I do not lust for checking this out before I see PD working with the Aukey charger and a proper cable... the hdmi port is also not a dealbreaker to me.

I'm really fed up with USB-C. It's overcomplicated and overpriced stuff. Imagine a certified charging cable supporting 5A/20V costs more than 35€ and its not perfect for fast data transfer, this needs a different winner which is weaker with charging performance... tell me the point of this?! It' nuts... cables that are thicker than the plugs, stiff and short... please makers, give us the ports we need inside the devices. The Hi13 has a lot of free space, it's not a crammed smart phone!

I'd have prefered a cheap, strong, simple stupid charging cable with a dedicated simple connector. No crossing, no complicated standards, no datalines, no configurarion bus, no negotiations.  
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szucsi| Post time 10-16-2017 08:36:53 | Show all posts
Edited by szucsi at 10-16-2017 08:39
artowi replied at 10-13-2017 15:04
I agree that it is unlikely for the damage to be caused by a current delivered thru a resistor with  ...

This is so true. The Ej898A can handle the 12V voltage as long as it is received from the appropriate pin. When on a USB-c cable, the connector moves (as it is a bad quality glued head) well, then the disaster occurs. In the opposite direction, Vc1 and Vbus are also supplied with a voltage of 12 volts. The EJ Chip was then burnt out. This is really a flame of the appliance. Reason: The tablet still works, but from now on, the EJ898A chip burns what a small volcano uses and consumes the charging current, transforms it to a great extent. The charger and tablet are too hot. If one of these devices is left on the charger, it is possible that when he returns, the whole house is burning.
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MemberChuwi| Post time 10-17-2017 06:04:29 | Show all posts
Edited by MemberChuwi at 10-17-2017 06:07

Referring to this quote I had mixed feelings because it's technically not quite ok. Overvoltage can destroy an input even without huge current, current is not the point. I didn't go into nit picking here in the first place because it wouldn't change much for the essential findings. On the other hand input pins are usually very high impedance too, so there is no sgnificant current either. Look at the resistors establishing the first 'static' negotiation phase then it's very likely input impedance is in MOhm range.  That doesn't help much if the inputs voltagře specs are exceeded.

It's like a valve that can't stand water pressure. However when it's cracked open a huge uncontrolled flow will follow, destroying everthing on it's way. The initial problem is the pressure (voltage), not the flow(current).
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MemberChuwi| Post time 10-17-2017 06:17:32 | Show all posts
I start to think Chuwi has messed up not only the charger's plug but the USB-C connector in Hi13 as well - because it's too deep. No USB-C plug I've compared the chuwi's with is as long. This by itself means potential issues with any cable you can buy not penetrating enough. Chuwi can't be serious expecting people doing some knifework to make things fit, do they? However this will not burn your device, just corrupt your data, sometimes, rarely, never,...?! Who knows.
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