I knew it would only be a matter of time before a Hackaday article on this would be posted:
The Cable Modem To SDR Transformation https://hackaday.com/2020/10/10/the-cable-modem-to-sdr-transformation/
The link to stdw's Github.io site provides a lot more information: Reverse engineering my cable modem and turning it into an SDR https://stdw.github.io/cm-sdr/
The webpage is an interesting read, if you are in to this sort of hackery. The cable modem is a Motorola MB7220. The Wave file of the received FM radio station is a bit rough and a bit over-driven, but very good for someone with little RF experience, but a desire to try and learn.
His webpage also references an SDR project that uses and Analog Devices cable modem chip: Hermes-Lite http://www.hermeslite.com/
It is far too easy to go down the 'rabbit hole' on this stuff!
73,
Mac / AE5PH
On 10/10/20 11:36 AM, Mac A. Cody via AMSAT-BB wrote:
Greg,
Interesting concept. Thanks for the post!
I scanned through the various sources and I cannot find which cable modem or firmware version is being used. I also looked through the companion Github https://github.com/stdw/bcm3383-reverse-engineering without gaining any insight.
Looking at the OpenWrt webpage you referenced, the only cable modem mentioned that specifically uses the BCM3383 is the Technicolor TC7200. There are probably others, though.
I hope that more development occurs.
73
Mac / AE5PH
On 10/10/20 6:35 AM, Gregory Beat via AMSAT-BB wrote:
Amateur Radio has a history of re-purposing Radio & Electronics surplus, for a variety of uses (receiving, transmitting, accessories, etc.).
Recent posting on Github the past two weeks https://github.com/stdw/cm-sdr
“cm-sdr” is a piece of software to turn a Broadcom BCM3383-based cable modem into a general purpose Software Defined Radio (SDR)
In its current state, cm-sdr serves as a proof of concept. It can currently stream I/Q data to a peer via TCP. A script to demodulate and play FM radio broadcasts is also provided.
cm-sdr is dependent on many functions and memory mapped registers in the unmodified firmware. Thus, at the moment it is highly tailored to one specific cable modem model and firmware version.
==
Earlier work by OpenWrt with the Broadcom’s BCM33xx chipset. https://openwrt.org/docs/techref/hardware/soc/soc.broadcom.bcm33xx
The BCM3383 DOCSIS 3.0 cable gateway System on a Chip (SoC) combines Broadcom's Full-Band Capture (FBC), dual-band concurrent Wi-Fi and a custom applications processor. https://www.broadcom.com/products/broadband/cable/modems/bcm3383 Current Broadcom cable modem SoC offerings https://www.broadcom.com/products/broadband/cable/modems
== greg, w9gb
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