Delta 2 Bluetooth

Reverse engineering of Delta 2 Bluetooth interface. No affiliation with Ecoflow.

What currently works:

• Turn on/off:
  • USB
  • AC
  • 12VDC output

Demo

The experimental/main.py script connects to the Delta 2 and let's you toggle the outputs. Follow the installation instructions for pybluez. The script must run as root. This is experimental. This might brick your device. I use linux, no other OS is tested, but it might just work for you.

Overview

The Delta 2 uses an Espressif bluetooth MAC Address (mine starts with 34:b4).

The Delta 2 offers up 3 attributes:

Bluetooth Attribute Protocol
    Opcode: Read By Group Type Response (0x11)
    Length: 6
    Attribute Data, Handle: 0x0001, Group End Handle: 0x0005, UUID: Generic Attribute Profile
    Attribute Data, Handle: 0x0014, Group End Handle: 0x001c, UUID: Generic Access Profile
    Attribute Data, Handle: 0x0028, Group End Handle: 0xffff, UUID: SDP
    [UUID: GATT Primary Service Declaration (0x2800)]
    [Request in Frame: 726]

In my traces the following handles were used:

• 0x002d SDP: RFCOMM Delta2->Phone
• 0x002a SDP: UDP Phone -> Delta2

RFCOMM status

The Delta 2 sends out a beacon every 500ms that likely contains all current information, such as charge, discharge, port states etc. I tried decoding this beacon in states and states2 but haven't had much success yet.

UDP Commands

Every action on the Delta 2 sends a UDP packet. I started labelling sample packets in commands. I have gotten some of them wrong, focussing on the data points I care about most rn.

Contributing

If you want to reverse engineer the connection from your Android phone to your bluetooth device, use the following process:

Prerequisites:

• An android phone with the app installed
• A way to record your screen
• A computer ideally with linux with wireshark and adb installed

Process:

• Connect phone via USB with Debugging turned on
• Enable HCI snooping
• (re-)enable Bluetooth
• Film your actions e.g. with a second phone or screen recording
• Open the app and do the thing you want to investigate
• Optionally: turn off blueooth and HCI snooping
• Retrieve the Blueooth snoop log
  • Either it is on the sd_card (wasn't for me), then do adb pull ... from the device
  • retrieve it via adb bugreport
• open the file in wireshark
• Try to establish a match between the video and the wireshark data. Tip: Jot down the times and their offsets on a piece of paper together with the performed action.

In rare cases the app is stuck for up to 3 seconds after pressing a button before sending the packet, introducing an offset.