Hardware issue on Hoover devices (No connection/No Wifi LED on)

[RubenKelevra]

I want to share my story here:

I noticed that my Washer-Dryer isn't connecting to wifi anymore, and the Wifi-LED stayed off.

I tried to reset via Wifi/Bluetooth - as I did made some config changes to my wifi in the past, and thought that's the reason, but no luck.

So I took my machine apart 2 weeks ago, and debugged the issue:

• The washing machine got a chip which does the washing programs (MCU), and an additional ESP32-Solo which does the Wifi/Bluetooth part of things.
• I've discovered, that the ESP32 is supposed to get a signal (hi signal with 3.3V) from the MCU on it's reset port, if it's supposed to be starting. Otherwise, it's low.
• The MCU runs with 5 V, so the output of the MCU is also 5V for the signal it's giving off to start the ESP32.
• To make the signal compatible with the ESP32, it's run through a voltage divider (basicly just two resistors, one is channeling the excess voltage to ground, the rest is received by the ESP32.
• One of these resistors was visibility charred (see attached image below) and did not read the printed on resistance, which did lead to a very low voltage being received by the ESP32, which was interpreted as LOW by the ESP32.

• Otherwise the board looked absolutely fine with no visible vapor or water deposits, so it's not caused by anything water related.

I'm not sure what caused this, but created a solution for everyone who wants to fix this issue (either before or after it occurs) for themselves.

First make sure you got the same/similar board layout:

• R44's right side (letters of R44 upright) should connect to a port on the MCU.
• Left side of R44 should connect to the RST port of the ESP32 (second pin on the left upper side - if letters are upright on the ESP32-Solo).
• R50 should connect as a voltage divider to R44 and on the other side to ground.

You will need:

• Soldering iron
• A bit of patience
• Some color coded wires flexible (a couple of cm long each)
• Hot glue gun
• Large heat shrink tubing
• Hot air gun
• AdUM1201 or AdUM1200 on a SOIC8 to DIP8 board with the aproporate chicken food already soldered on (e.g. this one from Ali)

Logic for the AdUM1201:

Process:

• Desolder R44
• Attach a wire at the right pad (if R44 lettering is upright) which goes to the MCU
• Connect this to the Input-Side of the AdUM1201/1200 together with a 5 V on the same side from the header pins (clearly labeled on the board as "MCLR +5V").
• Connect the ground from the same side to the header pins of the MCU (also clearly labeled as GND for "MCLR" on the board).
• Add a heat shrink tubing over the AdUM1201/AdUM1200 and move it a bit past the module.
• Connect the output side of the AdUM1201/AdUM1200 (of the same channel of course!) to the port labeled "EN" on the header pins for "WIFI PROG" (labeling is one row higher for the measuring pins, but you can see the traces going down to the header pins)

Visual of the header pin section:

• Connect power of the output signal side of the AdUM1201/AdUM1200 (which connects to the EN port) to "VCC" on the "WIFI PROG" port.
• Connect ground of the output signal side of the AdUM1201/AdUM1200 (which connects to the EN port) to "GND" on the "WIFI PROG" port.
• Pull the heat shrink tubing back over the AdUM1201/AdUM1200 and heat it up so it shrinks nicely over the module.
• Glue the wires and the module down onto the board, so it's vibration resistant. Make sure you don't glue it onto another component of the board which might produce heat. Choose an empty spot with just traces on the PCB!

Should in the end look like this:

---

I suggest doing this before the same fault happens, because in my case I suspect the 5 V somehow entered the ESP32 through the faulty resistor and caused issues on the ESP32's flash. I could read out the flash fine, but the ESP32 won't boot and throw a message about flash reading issues out.

I suspect it's just the configuration section which is not "well" readable, but I'm not sure atm.

But the ESP32 as well as the flash itself is fine. It seems to be just a software issue now.

If you want to read out UART the TX/RX pins of the "WIFI PROG" port are connected to the ESP32 and the "IO0" labeled port lets you put the ESP32 into flash mode, if you ground it. So you can use the flash tool do dump the flash content or upload a new firmware.

You can also safely boot the ESP32 alone, if you provide 3.3 V on the VCC port of the "WIFI PROG" header, in case you want to boot the ESP32 and look at the output without starting up the MCU, because you got it on the bench.