Re: [Gumstix-users] uart connection and avrisp problem

[Dave H. <dhy...@gm...>]

Hi Eli,

On Sun, Jun 7, 2009 at 4:18 PM, Eli Cohen<eli...@mi...> wrote:
> i connected an aerocomm ac4790 chip to the uart0 port on my robostix.
> i swapped rx and tx, checked for shorts, and everything looked good.
> when i go to program it, avr studio tells me that is has detected a
> short and won't program. when i unplug the rx and tx connections, i
> can program it no problem. in fact, i can program it that way, and
> then plug in my aerocomm unit and it seems to work. any ideas why
> connecting rx and tx to something else makes the ISP go nuts?

UART-0 Tx and Rx pins are also called the PDO and PDI pins which are
used for programming the ATMega128.

Normally, you can leave stuff attached if you put an appropriately
sized resistor inline between UART-0 and the device that's hooked up.
That way when trying to use the programmer, it will be able to
override the lines.

-- 
Dave Hylands
Shuswap, BC, Canada
http://www.DaveHylands.com/