AVR-Chat

If you plan to use the ISP and external circuits on the programming 
pins, Chris, you should always put a resistor in series with the 
external circuits so they don't load down the ISP signals ... not to 
mention possible unintentional damage to your external system in some 
manner.  An alternative would be to use a multiplexer similar to a 
CD4066 or a CD4052.  Jumper select the source when programming and 
you're good to go.


REB


xolang1 wrote:
> Hi Guys,
>
> I have a board with atmega128L and have sucessfully programmed the chip using an AVRISP. However after adding some components on board, I get "AVRISP Error entering programming mode" in codevision and a similar message in AVRstudio.
>
> - I know that the AVRISP is working as I have been able to program another circuit board w/ a mega64.
> - I tried using STK500 programmer with the mega128 board, but I get the same error.
> - the programming pins are directly connected to the AVRISP port via 600ohm ferrite beads.
> - I tried to insert a 12k pull up resistor on the reset pin, but same reults
> - The components I have added before the board wont program are several zener diodes across some GPIO's and 2 vibration sensors.
> - The last code I have programmed on the chip seemed to work. so i could not be certain if it is the chip that is damaged.
> - changing the chip would be the last option as i have already changed
> before and the PCB is starting to be damged. I would really appreaciate 
> if u guys could enlighten me on how to proceed.
>
> thanks!
>
> Chris
>