General Advice

Do you have a question? Post it now! No Registration Necessary

Translate This Thread From English to

Threaded View
I need some input on what the best microcontroller (relatively cheap) and OS
to use for a project I will be starting soon.

The project requires a Ethernet connection, so an on-board MAC is desirable.
A real time clock and several timers will be required.
The MCU will need to interface with a RC5 encoder for IR control of devices
(and possible RF communication as well).

On the software side, the device needs to run either HTTPd with SSL or a
custom daemon which includes encryption (probably blowfish).  It will also
need to run a NTP client to update the clock at regular intervals.
The main function program will send commands to various devices through
IR/RF and by operating relays at certain times as defined by a remote user
via the daemon.

Of course, if this seems impossible to implement without a MMU OS, I am
willing to accept suggestions of MCUs with MMUs or possibly multiple chip
Naturally, I would like to minimize the cost of the project.


"Remove the spam to e-mail me"

Re: General Advice
Your requirements don't directly mandate an MMU, but you'll possibly
wind up with one for free anyway. Sharp has an ARM7 with on-chip MAC
that might be interesting. LH79525,

You can actually do everything you want in an OSless 8-bit micro, but
the annoying part is sourcing and integrating the MAC. I'd suggest that
Sharp part and eCos.

Re: General Advice

Quoted text here. Click to load it

Zilog eZ80f91 sounds about right. They are a bit expensive in small
quantities, but otherwise seem to have everything else you want.
Development system with C, OS and lots of examples $99 I think.

Paul Burke

Re: General Advice
Quoted text here. Click to load it

See Rabbit Semiconductor as a starting point.  They make 8-bit modules
that have Ethernet and limited SSL support.

These guys may have SSL in the works:


Re: General Advice
Quoted text here. Click to load it

Maybe check out Axis ETRAX MCM4+16, or the 100LX. /.
I use these. Let me know if you want more info from my perspective.

Re: General Advice
Quoted text here. Click to load it

If you want to run SSL you will need a 32 bit processor (maybe you get away
with 16 bits with clever coding and fast enough clock). For an 8 bit
processor AES is a better choice than Blowfish. Or use a crypto-coprocessor
(which are rare and expensive) or a DSP


Re: General Advice

Quoted text here. Click to load it

See _Implementing SSL on 8-bit micros_ at

Re: General Advice

Quoted text here. Click to load it
Quoted text here. Click to load it
Interesting article! Is RC4 freely available today or covered by patents?
Some time ago it was a Mirocsoft prorietary algorithm.


Re: General Advice

Quoted text here. Click to load it

Close, but incorrect.  RC4 is and always has been owned by RSA
Data Security, Inc.  Jim Bidzos, President of RSA, decided long
ago to not patent RC4 but to instead rely upon trade secret
protection - which means that RSA has never revealed the RC4
algorithm to the public, a requirement for obtaining a patent.

Revealing, publishing, or using a trade secret is not illegal.
Trade secrets are protected by contracts instead of laws.
If you have signed a contract with RSA, you are bound by that
contract and could be sued if you violate it.

If, on the other hand, you don't have a contract with RSA and
are using a copy that has been reverse-engineered, you are free
and clear to use it.

An interesting aspect of this is that we don't *really* know
whether what we call "RC4" is the same as the RC4 owned by RSA.
We do know that the two can encrypt and decrypt each other's
output, and that this has been tested on millions of files.
For this reason, some people call the RC4 that we use
"ARCFOUR" instead of "RC4."

Bottom line: go ahead and use it.    

Guy Macon

Re: General Advice

Quoted text here. Click to load it

Nonetheless, RC4 is a trade secret, whether you think so or not.

Quoted text here. Click to load it

In other words, something that we are pretty sure is RC4,
but we are not completely sure ss RC4, puplished by someone
who may or may not have correctly reverse-engineered RC4.

Quoted text here. Click to load it

Comments by pepole who *don't* own RC4 have no validity.  
The official comment by the people who *do* own RC4 is:

"RSA Security does not hold any patents nor does it have any
pending applications on the RC4 algorithm. However, RSA
Security does not represent or warrant that implementations
of the algorithm will not infringe the intellectual property
rights of any third party. Proprietary implementations of the
RC4 encryption algorithm are available under license from RSA
Security Inc. For licensing information, contact: RSA Security
Inc. 2955 Campus Drive, Suite 400, San Mateo, CA 94403-2507,
USA, or ."

Quoted text here. Click to load it

Are you implying that RSA does not own RC4?

Re: General Advice
Guy Macon wrote on Mon, 13 Dec 2004 04:36:09 +0000:
Quoted text here. Click to load it
Quoted text here. Click to load it
If RC4 isn't a secret, it isn't also a trade secret. IMO it is
logical for an average engineer. Although I agree that lawyers (and
marketroids) use different kind of logic. ;-)

Quoted text here. Click to load it
Free RC4 implementations have been widely used for 10 years. IMO it
is long enough to prove that they actually implement RC4.

Quoted text here. Click to load it
I'm not. I'm only saying that R. Rivest is the inventor of RC4.
Another interesting link:


Site Timeline