add esp32 brownout / dump info

README.md

@@ -34,7 +34,8 @@ This also generates the replacement CA for the toniebox ```certs/server/ca.der``
 If you are using docker, this will happen automatically.
 
 ### Dump certificates of your toniebox
-You'll need the ```flash:/cert/ca.der``` (Boxine CA), ```flash:/cert/client.der``` (Client Cert) and ```flash:/cert/private.der``` (Client private key). Place those files under ```/certs/client/*```
+You'll need the ```flash:/cert/ca.der``` (Boxine CA), ```flash:/cert/client.der``` (Client Cert) and ```flash:/cert/private.der``` (Client private key). Place those files under ```/certs/client/*```. You can either power the box with the battery (be sure it is note empty) or with the power supply. (recommended)
+
 #### CC3200
 You can use the [cc3200tool](https://github.com/toniebox-reverse-engineering/cc3200tool) to dump your certificates over the Tag Connect debug port of the box. If you have installed the HackieboxNG Bootloader you should already have those files in your backup.
 ```
@@ -49,6 +50,7 @@ cc3200tool -if cc32xx-flash.bin -d cc32xx read_all_files extract/
 #### ESP32
 You can extract the flash memory via the debug port of the box and the esptool. Keep your backup!
 Please connect the jumper J100 (Boot) and reset the box to put it into the required mode. Connect your 3.3V UART to J103 (TxD, RxD, GND).
+If connected with the Boot jumper, the box just start in "DOWNLOAD (USB/UART0)" mode. (Check with a serial monitor). Beware, if the serial monitor is open it will block esptool.py from accessing the esp. If you get a "BROWNOUT_RST" check your power supply / battery. "SPO_FAST_FLASH_BOOT" indicates a boot without the J100 jumper. 
 
 ```
 esptool.py -b 921600 read_flash 0x0 0x800000 tb.esp32.bin