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BrantB
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Joined: 27/10/2017
Location: Canada
Posts: 40

Posted: 08:57pm 26 Mar 2018

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Hello Fellow MM-ers,

I mostly target my development towards an MMX platform, although for "simple" stuff, the "plain" MM (that's almost an insult, but not intended as such) is quite useful/capable.

As such, I have looked in the fundamental MM manual, and I see that "any" baud rate (up to the stated limits) should be workable. It goes further, to provide an example of 1111 baud. Great!

I don't see anything to the contrary in the MMX manual, so I think "great!" still applies here, too.

Brief background of the challenge: I have an unfortunate need to deal with some non-MM devices which all use a 16MHz crystal. If I had my 'druthers, I would use a baud rate of 115.2K for inter-device communications. However, at 16MHz, that doesn't work out so well.

I have already confirmed that 125K is a perfectly "doable" baud rate for the non-MM device - and, of course, it divides quite nicely from a 16MHz clock source. (That is the whole point of this, after all

.)

So, all I am really looking for here, is some confirmation from the "much more experienced than me" MM/MMX gurus, that you don't foresee any issues trying to use 125Kbaud on the MM/MMX side of things. Any particular pitfalls you think I should look out for?

Cheers!

Brant

Grogster

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Joined: 31/12/2012
Location: New Zealand
Posts: 9750

Posted: 12:06am 27 Mar 2018

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No, I don't think you should have any issues. So long as the baud-rate is the same at both ends, it should just work. Ultimately, you need to bench-test the idea to prove it DOES work. Most people elect to use standard baud-rates, but the MM can use whatever baud-rate you like, which is a nice touch if you want to keep your data as serial, but the baud-rate more secret.

The only real difference between the MM2(170 chip) and MM+ and MMX chips, is that the latter units run with a faster clock, so can make use of much faster baud-rates. The UART itself does not care.

Therefore, on an MM+ or an MMX, an 'Odd' baud-rate of something like "123456"(123k4) should work just fine - so long as it is the same at the other end as mentioned above.

Smoke makes things work. When the smoke gets out, it stops!

BrantB
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Joined: 27/10/2017
Location: Canada
Posts: 40

Posted: 06:24pm 27 Mar 2018

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Thanks, Grogster. Always nice to have a sanity-check.

Although I am being 'forced' into the realm of non-standard baud rates in this case, I must admit that I had never thought about doing it as a deliberate annoyance to would-be snoops. Hmm. That is amusingly warped - I like it!

For sure, the next step is to bench/stress test.

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