Re: [avrdude-dev] USART1

[Erick Castillo]

On Sun, 27 Apr 2003, Brian Dean wrote:

> On Sun, Apr 27, 2003 at 03:44:01PM -0700, Erick Castillo wrote:
>
> > that USART1 has the pins for MOSI and MISO for serial programming. Will I
> > still be able to program the atmega128 if I program it to use USART1 at
> > port E? Will i have to go through some special procedure to program the
> > chip again if I'm using USART1 for other things during operation?
>
> Mainly you'll want to design your external circuitry so that it does
> not interfere with ISP programming, whether this be through manual
> jumpers that can be removed during programming, or by using logic to
> respond to the /RESET signal which disables (goes to high impedence
> state) any circuits that share the ISP lines.  For example, if you
> plan to use an RS232 level shifter on the PORTE uart, consider using a
> MAX3222, for instance, which has ENABLE and SHUTDOWN lines that can be
> interfaced to the /RESET line.

I can see how disabling the external circuitry with jumpers might work,
but what about the software side. Suppose I program PORTE or USART1 so
that there is continous activity through those lines. Will I have to
explicitly disable the UART in order to program it using those same lines
or can I simply start the download?

I guess my major concern here is, should I use the PORTE USART pins only
for serial programming or is there an easy solution for using both. The
problem is, I have the second USART doing something else that NEEDS to be
done so I can't just use that one for a PC interface to the controller.
I can dedicate PORTE to serial programming but I would like to have access
to both. Any more suggestions would be appreciated. Thanks.

--Erick