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Micro USB port draws too much power

Posted: Fri Feb 28, 2020 6:34 am
by paulcrawford
I have been successfully using the @ytrikoz firmware on my SmartPower 2 for several months viewtopic.php?f=86&t=35445.

I use the microUSB port connected to a linux PC running PlatformIO to update the firmware which has also always worked fine. But today when I wanted to update the firmware, plugging the USB cable into the linux PC (actually a Mac running linux under Parallels) resulted in the a "USB Accessories Disabled" error noting that the power drawn by the USB cable was more than could be supplied. This meant it was not possible to update the firmware via the microUSB port.

In previous testing of the SP2 I connected the SP2 microUSB port to my N2 while the SP2 was supplying power to the N2 (I have modified the SP2 to run at 12.7V by changing R30). With that connection I could see the data coming from the SP2 on the N2 so I know that was working.What I also noticed though was that the current supplied by the SP2 increased significantly when the SP2 microUSB was connected to the N2 USB. I thought I could determine the specific current by using a USB CHARGER Doctor in the connection. I connected the USB CHARGER Doctor via a male/female USB-A cable to the N2 and the input to the USB CHARGER Doctor. The USB CHARGER Doctor showed about 5.09V and 0.01A when connected only to the N2. When I connected the USB-A connector from the SP2 microUSB port the USB CHARGER Doctor screen went blank but came back on when the SP2 was disconnected.

I am fairly confident that making that connection is what appears to have damaged the SP2 microUSB port causing it to draw too much power.

I have tried a different (known working on another device) microUSB to USB-A cable but still get the same error. I have also reset the PRAM and SMC on the Mac with no effect on SP2 microUSB connection.As well, I have connected a USB logic analyzer to the Mac and it works fine with no errors.

Is there anything I can do to repair the SP2? It still works as a monitor with the present firmware but I cannot update.

I am also concerned about connecting the SP2 directly to the N2 in case there is a problem because of the increased power draw.

Re: Micro USB port draws too much power

Posted: Fri Feb 28, 2020 5:30 pm
by odroid
Do you mean the SP2 works fine except for the micro-USB port?
We will install the custom firmware early next week and keep running it to reproduce the issue. It is already Friday evening here.

Meanwhile, look into the USB-UART IC on the board to check whether it was burned or not.

Re: Micro USB port draws too much power

Posted: Fri Feb 28, 2020 10:48 pm
by paulcrawford
Yes, the SP2 works perfectly except for the micro-USB port.

This is a photo of U1. No damage that I can see.
USB-UART IC U1.png
USB-UART IC U1.png (735.61 KiB) Viewed 3086 times

Re: Micro USB port draws too much power

Posted: Mon Mar 02, 2020 10:31 am
by lsc1117
If you don't mind, try to clean the part of the red circle in the picture below to clean the leads with a toothbrush to remove any extra particles.
USB-UART IC U1.png
USB-UART IC U1.png (754.02 KiB) Viewed 2932 times

Re: Micro USB port draws too much power

Posted: Mon Mar 02, 2020 11:15 pm
by paulcrawford
I cleaned the red circled area with 99.9% isopropyl alcohol and a hog hair cleaning brush. Then tested the port again. No change; still drawing too much power.
IMG_0837.png
IMG_0837.png (1.87 MiB) Viewed 2872 times

Re: Micro USB port draws too much power

Posted: Wed Mar 18, 2020 11:04 am
by paulcrawford
@lsc1117,

Any further thoughts?

Re: Micro USB port draws too much power

Posted: Wed Mar 18, 2020 11:56 am
by lsc1117
@paulcrawford

I couldn't reproduce that the USB port broke in the same environment as you.
I assume that the USB port was damaged by static electricity.

Re: Micro USB port draws too much power

Posted: Thu Mar 19, 2020 10:40 am
by paulcrawford
Is there anything I can replace on the SP2 board? Is it likely that the CP2104 user chip is damaged? Or am I forever stuck with the present firmware? Or do I have to buy a new SP2 and replace R30 with a 91KR again?

Re: Micro USB port draws too much power

Posted: Thu Mar 19, 2020 10:54 am
by odroid
It is really hard to know which portion is really damaged at this moment.

Can you measure the voltage on the C1 P3V3 power rail with a DMM? It is worth to check if micro-USB cable connection causes any voltage drop or not.
https://github.com/hardkernel/smartpowe ... power2.pdf

Meanwhile, I will check whether we can sell the SP2 board separately or not.

Re: Micro USB port draws too much power

Posted: Thu Mar 19, 2020 11:19 am
by paulcrawford
I will check the voltage on C1.

Re: Micro USB port draws too much power

Posted: Thu Mar 19, 2020 9:53 pm
by paulcrawford
C1 is 3.289V

Re: Micro USB port draws too much power

Posted: Fri Mar 20, 2020 10:31 am
by odroid
Is it always 3.289Volt regardless of the micro-USB connection?

BTW, I heard we might be able to sell the SP2 board separately at $15. But the shipping cost is still very high and you probably don't like this option.
Just remove the CP2104 from the board and connect a cheap 3.3Volt USB-UART cable and try uploading firmware.
You need to wire five signals RXD, TXD, DTR, RTS and GND.

Re: Micro USB port draws too much power

Posted: Sat Mar 21, 2020 3:13 am
by paulcrawford
@odroid

Just to confirm your suggested modifications, can you please verify the solder points for wires to my USB-UART TTL adapter.

For the CP2104 removal, can I cut it carefully at the pins with an Olfa knife, or do I have to unsolder it?


USB-UART modifications.png
USB-UART modifications.png (1.12 MiB) Viewed 1993 times
Thanks.

Re: Micro USB port draws too much power

Posted: Mon Mar 23, 2020 10:36 am
by lsc1117
All pins are okay include DTR and RTS on the TR(Q1, Q2). You mean DTR instead of DTS, right?

I recommend unsoldering the CP2104 with a heat gun.
If you don't have a heat gun, take care to remove with your Olfa knife.
It has been soldered with GND under the CP2104. So it's a little hard to remove with the knife.
Image

Re: Micro USB port draws too much power

Posted: Mon Mar 23, 2020 12:14 pm
by paulcrawford
Yes, DTR. Sorry.

If I cut the pins flush with edge of the chip does the whole chip need to be removed since it will only be connected to ground from the bottom?

Re: Micro USB port draws too much power

Posted: Mon Mar 23, 2020 1:41 pm
by lsc1117
Because the chip is QFN type, it might remain connected I think.

Refer to page 37 of the datasheet.
https://www.silabs.com/documents/public ... asheet.pdf

You should also cut the bottom of the pins of the chip if it's possible.

Re: Micro USB port draws too much power

Posted: Mon Mar 23, 2020 10:46 pm
by paulcrawford
I have been reviewing hot air guns for desoldering. Can you recommend a device? I have seen both 450 and 650 W tools. 3mm nozzle seems to be the smallest available. Will that size allow me to remove the chip without disturbing other nearby components? What about controls in the handle vs separate box?