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Author Topic: How to make an Arduino-compatible minimal board  (Read 5356 times)
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I have done a fairly lengthy post about how to make a breadboard "Arduino-compatible" setup ...



With the aid of an FTDI cable you can program your breadboard from the Arduino IDE, just like a normal board:



The post describes wiring, how to install the bootloader, and other details:

http://www.gammon.com.au/forum/?id=11637
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I just got a FTDI cable (yea behind the times) and read in some very old post that RTS wouldnt work for reset, is that changed?

http://arduino.cc/playground/Hacking/FTDIAutoReset
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You've got me worried now! It's working, but maybe it shouldn't be ...

Well with the cable I have, which I think I got from Adafruit, this is what I see on the RTS and Reset lines (ie. before and after the capacitor):



It looks like RTS is going low (and stays low) which causes Reset to pulse low for about 1 mS.
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I just got a FTDI cable (yea behind the times) and read in some very old post that RTS wouldnt work for reset, is that changed?

http://arduino.cc/playground/Hacking/FTDIAutoReset

I believe the very first arduino board designed to have a auto-reset function used the RTS signal. On later versions they changed the hardware to use DTR instead, but for legacy compatibility reasons had the IDE pulse both DTR and RTS. Not sure that is still the case or not as sometime in the version changes they handed off the activation of the control signal(s) from the IDE directly to AVRDUDE directly. But Nick's example implies the RTS is still pulsed.
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I couldn't get it to work at all if I moved the pin to the "free" spot on the FTDI header (the one I have labelled CTS). A check with the scope appears to show it is not pulsed.
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well yea CTS was never in the equasion, its been typically on DTR (or apparently RTS back in the day?), which is not broken out on FTDI cables

you would have to cut open the USB end of the cable and find DTR, I was lazy and reset never worked with my MCP2200 (or whatever microchips pic made USB bridge thing is) so I just got used to hitting the button since my POS dumpster computer does not have a serial header broken out (though the pad's are on the mobo, its wonky as it is and not worth messing with as its being replaced soon)
« Last Edit: May 09, 2012, 12:08:21 am by Osgeld » Logged


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That's a very nice set of instructions.  Is the Programmer sketch based on other code such as Optiloader or Adaloader, or is it a new ground-up rewrite?  I've been trying to use Adaloader to re-write an ATmega8U2 chip without success (I believe the problem is related to the flash page size).  Do you think your Programmer sketch could be adapted to other chips?
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It's a complete rewrite based on reading the datasheets.

Because it programs the Atmega2560 I believe it handles flash page sizes correctly (until you exceed 0xFFFFFF).

It should be adaptable to other chips because the programming information is in a table.
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Hmm, very nice indeed!  Time for a printout...
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Has this issue been resolved anywhere? regarding which pin to use RTS or DTR for auto Reset?
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What I described on that page works for me, if that answers your question.
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I will plug it in tonight and post what I find, if its working for nick I would bet it would work for me as well
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  Awesome write-up Nick! I learned a few things, and the pictures are excellent!
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How about a '1284 version Nick smiley
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Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

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Do you mean the bootloader, or the whole thing?

I've just ordered the processor, I'll give it a try.
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