So, if I understand this correctly: - Fuses can not be programmed in dW mode, but you can get out of dW mode into ISP mode temporarily (to unprogram fuses vie ISP) - Avrdude will attempt to connect in dW mode and to switch to ISP when the initial connect via ISP fails. So I can use avrdude -P usb -c dragon_isp -p t85 -v -U hfuse:w:0xDF:m to clear the DWEN fuse even is the chip is in dW mode (DWEN fuse programmed).
My ISP connection is functional and there is nothing connected to reset except the dragon. Thanks Markus On Mon, Apr 18, 2011 at 08:14, Joerg Wunsch <[email protected]> wrote: > Markus Baertschi <[email protected]> wrote: > > > I did presume that using this I can go back to ISP: > > >> avrdude -P usb -c dragon_dw -p t85 -v -U hfuse:w:0xDF:m > > No. dragon_dw cannot reprogram fuses, as debugWIRE mode cannot handle > that. You have to use dragon_isp again. It will fail in the first > attempt, but then issue the sequence to get out of debugWIRE. After > this, you have to re-issue the (ISP!) command, and it's supposed to > work. > > Of course, nothing mandates you'd have to reprogram the fuses at this > point at all: debugWIRE mode is just left temporarily in order to > assign the /RESET pin to the ISP algorithm again. This state lasts > until the next power-cycle, at which point the DWEN fuse will be > evaluated again. So, if you intend to continue debugging, you could > as well just use ISP mode to download new firmware (my experience says > it's often faster and more reliable than within debugWIRE mode), and > then just power-cycle to start a new debugging session. > > Obviously, your debugWIRE mode must be functional in order to get out > of debugWIRE. If there are hardware issues that make debugWIRE mode > not work (too much capacitive load at /RESET etc.), all this wouldn't > work at all. > -- > cheers, J"org .-.-. --... ...-- -.. . DL8DTL > > http://www.sax.de/~joerg/ NIC: JW11-RIPE > Never trust an operating system you don't have sources for. ;-) > > _______________________________________________ > AVR-chat mailing list > [email protected] > http://lists.nongnu.org/mailman/listinfo/avr-chat > -- *Markus Baertschi*, Bas du Rossé 16, CH-1163, Etoy, Switzerland [email protected], ++41 (79) 402 1186 (mobile)
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