[amsat-bb] Re-purpose Cable Modems, headed to dumpsters ?

[Mac A. Cody]

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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>
> _______________________________________________
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> to all interested persons worldwide without requiring membership. 
> Opinions expressed
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> of AMSAT-NA.
> Not an AMSAT-NA member? Join now to support the amateur satellite 
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