ESP-Bridge

Framed binary USB bridge protocol for talking to an ESP32 from Termux — or any Linux host — no root required.

This is the transport layer extracted from NRSuite. It doesn't know anything about Wi-Fi, packet capture, or any specific use case — it just gets JSON commands and binary chunks reliably between an ESP32 and a host process over USB CDC, with automatic root/no-root backend detection. Use it to build your own ESP32-to-Termux tools.

Pairs with the BridgeProtocol PlatformIO library on the firmware side — install both and the two speak the same frames out of the box.

Install

pip install espbridge

or

git clone https://github.com/7wp81x/ESP-Bridge
cd ESP-Bridge
pip install -e .

On stock Termux you'll also need:

pkg install python termux-api libusb

plus the Termux:API app from F-Droid (not the Play Store version).

Quick start

See examples/echo_cmd.py for a full runnable example. The short version:

import os, espbridge as eb

backend = eb.detect_backend()          # "termux" or "root"
device  = eb.wrap_fd(int(os.environ["TERMUX_USB_FD"])) if backend == "termux" \
          else eb.wrap_direct()

ep_in, ep_out, iface = eb.get_cdc_endpoints(device)
eb.claim_device(device, iface, fd_wrapped=(backend == "termux"))
eb.reset_endpoint_toggles(device, ep_in, ep_out)

sender   = eb.Sender(device, ep_out)
receiver = eb.ReceiverThread(device, ep_in); receiver.start()
proto    = eb.Protocol(sender, receiver);    proto.start()

resp = proto.send_cmd("PING")          # blocks until RESP or timeout
print(resp)

Frame format

[MAGIC 2B: 0xAD 0xDE][TYPE 1B][ID 1B][LENGTH 4B LE][PAYLOAD NB]

Type	Hex	Direction	Payload
CMD	0x01	Host → ESP32	JSON {"cmd": "...", "args": {...}}
RESP	0x02	ESP32 → Host	JSON response, matched by frame ID
EVENT	0x03	ESP32 → Host	Async JSON, id=0
PCAP	0x04	ESP32 → Host	Raw binary chunk (id = chunk index) — despite the name, use this for any binary stream
ACK	0x05	Host → ESP32	JSON {"chunk": N} — flow control
HTML	0x06	Host → ESP32	Chunked raw payload upload

Commands (CMD) are entirely up to you — define whatever cmd strings and args your firmware understands. This library only handles framing, transport, and request/response matching.

What's included

• protocol.py — frame builder/parser, Protocol class (send_cmd/on_event/on_pcap)
• sender.py — thread-safe bulk OUT writer with retry
• receiver.py — background bulk IN reader thread
• usb_device.py — root vs. no-root backend detection, permission flow, endpoint discovery

License

MIT