questions regarding debugwire

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Hi - it seems I'm one of the lucky few that is getting a free AVR Dragon. So now, I am working out how I can use one on my current AVR project. The primary differences between that and the boards I built is that I currently have 0 ohm, not 10K ohm, resistors on the SPI lines, as well as a 10K pull up resistor on the MCP2515 CS' line.

Will debugwire work on this board? I read that for debugwire support you must have a 10K or greater resistor on the reset line, no capacitor on the reset line, and no external reset sources. The capacitor can easily be removed from the board, but will that cause stability problems? The supply should be fairly clean, if it matters. That is untested at this point, however. Will the MCP2515 cause problems? I don't think I can use the debugwire for testing out the code while it is running (as it'd constantly shut off the MCP2515, which would cause issues), but can I at least use it for programming the chip?

Also, Is debugwire any faster than ISP? I can normally use my original serial AVR-ISP at full speed with no issues, so it's fairly fast. The big advantage that I'm seeing by switching to debugwire is that I can get rid of the bulky 2x3 ISP pin header and replace it with a 1x3, which on this board is a very large space savings.

Thanks!

Last Edited: Sat. Aug 18, 2012 - 08:06 PM
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Surely somebody out there has used debugwire?

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I've used it for M168s but only on an STK500 but I guess the schematics of that board (in AVR Studio help) are always a good reference to start working from.

Speed-wise it certainly seemed at least as fast as ISP programming (the debugger downloads the image each time you start to debug) but the real advantage is clearly not just the altrenate programming mechanism but the visbility of what's going inside the chip and therefore the far enhanced debugging capability.

Cliff