BTW, is there an easy way to autodetect the baud rate while using an AVR UART? (Preferably something that works with ATmega8, given that those MCU's are such a cheap thing nowadays.) There're some ideas (and 8051 code) for that on [1], but I'd like to know if there could be any better techniques. TIA. [1] PS. It seems that I'm slowly drifting into designing my own, AVR-based Bus Pirate clone. The good news is that the parts for this one will likely cost under $10... (connectors included.) -- FSF associate member #7257

It's pretty straightforward if you can use a timer capture pin; it takes care of grabbing the timer count on the active edge and you can examine it at leisure. Essentially, you will want to listen to an incoming serial stream to measure the narrowest pulse and when you've seen enough identical pulses, that determines the rate. If you get a narrower pulse (that is wider than a glitch width), start the count over. A little more robust is to add N to an accumulator when you see a pulse within epsilon of the current narrow width, subtract M if there is a wider pulse, or reset to zero and start over if there is a narrower. When the accumulator reaches Q, you've found the pulse width. If it counts down to zero (from too many wider pulses), assume you saw a narrow noise pulse and start over. A divide-by-16 (>>4) works pretty well for epsilon. -- Rich Webb Norfolk, VA

baud rate autodetection on AVR 8-bit?

Dec 07, 2012 104 Replies

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Rob Gaddi 13 years ago

I haven't tried it under Windows, but I just used the Linux version of mspgcc for a personal project, and was really impressed by how clean and easy it wound up being. You also need mspdebug if you're going to work with a LaunchPad, but once I got them installed things just did what they were supposed to.

Rob Gaddi, Highland Technology -- www.highlandtechnology.com Email address domain is currently out of order. See above to fix.

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Jon Kirwan 13 years ago

Wonderful to hear. That was next on my list to try out, as well. Good news!

Thanks, Jon

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Waldek Hebisch 13 years ago

Look at msp430f550x series. IIRC the cheapest one has has TI suggested retail price 1.6$. However, RAM is much bigger than 512 bytes: all in the series have

2kB RAM for USB controller and 4kB data RAM.

Waldek Hebisch hebisch@math.uni.wroc.pl

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Waldek Hebisch 13 years ago

Oops, msp430f550x is device only...

Waldek Hebisch hebisch@math.uni.wroc.pl

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Jon Kirwan 13 years ago

Thanks for checking on it. I was about to do that, today.

Jon

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