DSO HW V2.81 working partially only with USB

Hardware: 2.81
DFU: V3.40C
SYS : Custom 1.69
APP : 1.13

While working on improvement to the 1.64 SYS, Windows warns me about a peak consumption error on the USB port connected to the DSO Quad. I was not upgrading firmware, neither testing it. After that,

DSO unplugged from USB:

  • The device just shows a white screen whatever button pushed at start.
  • No DFU possible
  • Checked the battery, 4.2v with my multimeter (fully charged)

DSO plugged to USB:

  • The device starts, with a short white screen
  • On DFU mode, Windows shows an unrecognized device
  • On Application mode, “Parameter record not found” and Windows shows an empty drive and impossible to format it
  • Vbt=+5.60V in V1.13 APP whatever the USB port plugged in (PC, USB charger, 10xHUB)
  • Screen is like blinking a bit (over lighted?)
  • If USB is unplugged, the screen goes white immediately (This makes hard any debugging attempt…)

My first opinion is that something wrong with the power regulation parts.
SeeedStudio teams, Could you help me?

DSO SYS select 2.jpg
APP started.png
USB unplugged.png


my DSO203 v2 (2.81) does behave almost exactly the same as yours after sys upgrade to 1.63 from 1.62. The APP1 v1.13 does start, but is uncalibrated and looks exactly like on your screenshot. The batt voltage is wrong too. The white screen does happen after I let the battery drain a bit. USB is not recognized unless the battery is disconnected, power is fed only through USB and only in APP1 mode. In DFU the USB is not recognized and thus no firmware flashing is possible.
I thought that my charging circuit has died, too. But as I found your post with the exact same symptoms, maybe it is a something like bootloader corruption and there is a solution. Please let me know if you found something out.


I had similar problem with my DSO HW V2.72. It was usually working for couple of minutes. It then started to be unstable with following symptoms:

  • random resets
  • higher brightness with wave like refresh/blinking
  • higher Vbt reading over 5V

I’ve looked at schematic (seeedstudio.com/wiki/File:DS … 31106_.pdf) and identified issue to be - most probably - U15 (QX3406AL). I’ve checked the U15’s Vin voltage and there was a difference of ~0.02V between the good and bad state. This seemed to be enough to cause the higher brightness with wave like refresh/blinking. The Vbat from schematic had difference around 0.125V between good and bad state which caused higher Vbt reading. The voltage at SW (leg 3 of U15) was 2.42, ~0.4V less than it should be which most probably caused the random resets because it is ARM chip power supply. The voltage readings had some dynamic factor in it. The Vbt readings were floating, random resets were occurring…

I decided to replace the U15. I couldn’t get the QX3406AL however. Hardware seemed to have a different chip anyways. Most probably HX1001 based on HX_VG marking on the chip. I got LTC3406ABES5. It is from the same family of the synchronous buck DC/DC converters as the previously mentioned ones. Removed the old one then soldered new one, checked connections, crossed fingers, turned on… Works fine! :slight_smile:

Symptoms you experience are similar to those I have been experiencing. There is a probability your DC/DC converter is broken too.

I confirm the solution given by elju .
I removed the voltage regulator U15 and soldered an LTC3406ABES5
and the DSO203 (HW version 2.72) now works perfectly.
Thank you very much elju.