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Microcontroller Programming » Using pins the BootLoader uses

May 13, 2014
by Blackwatch42nd
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I'm sure this has been answered before, but can't find it:

I'm trying to Use pin 14 (on a 168) as an output (simply turn an LED on and off), but the way I seem to understand (and I don't understand much) is the Boot Loader uses pin 14 to determine whether to go into the programing mode or run mode.

Here's what's happening: Once the chip is programmed and I place a connection from pin 14 to resistor to LED to Ground and then power up, it seems the chip thinks it's in the program mode and does nothing. If I wait to make the connection till after power up, it works like I programmed it.

Is there a way to bypass the boot loader check of pin 14 with out changing the boot loader?

Thanx John

May 13, 2014
by Rick_S
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No, but you could reverse your LED so that the anode is tied to VCC through your resistor and you pull it low with the micro. This would have the leg pulled high at boot allowing to bypass the bootloader.

May 14, 2014
by Blackwatch42nd
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Rick,

That worked, thanx! Wish I had thought of that first. My first thought was those lines, but it involved transistors, a large Faraday cage and sixteen hamsters. Simple is better.

Now, is there a simple way to do away with the external crystal without changing the fuse settings?

Thanx again John

May 14, 2014
by Rick_S
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Unfortunately no. If you want to eliminate the crystal altogether, you have to change fuses.

May 14, 2014
by Blackwatch42nd
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Rick,

So much for an easy way out. OK, thanx for the reply

John

May 16, 2014
by Rick_S
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No problem, good luck with your project.

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