AVR-Chat

May I try and warn you that the resistors you are contemplating using, could allow more current than many PPorts can supply....
Please check on the web yourself, but generally speaking, you cannot rely on sourcing more than 2.5ma or sinking more than 24ma. In fact some cannot even sink that much.

A place to start is here:-
http://www.lvr.com/files/ibmlpt.txt

If you are just using a plug in LPT: card in a PC, blowing it is of almost no concern (I would NOT use the mainboard printer port for anything other than a printer as its part of the mainboard chip set nowadays!!) as a cheap replacement will get you up and running again.

Be more careful with a laptop, there are plug in cards that can safeguard the onboard Pport...do use them.....or use a laptop that you can throw away if needed.....replacing a mainboard is not what you want to have to do!!!

Plus you have the problem that some laptops only have 3 or 3.3volt printer port signals in the first place......

Do not be offended by my mentioning this, many forget to watch out here, many company produced PPort breakout PCBs also have resistors of too low a value to be safe, and they should know much better.....
Regards

--- In AVR-Chat@yahoogroups.com, art3@... wrote:
>
> I am designing a robot and used an ISP based on the Sample Electronics
> programmer cable.  This ties printer port pins through 360 ohm resistors
> to the programming port pins on the AVR.  The chip that I am using is the
> Tiny2313.  I also have a FAN8200 H-Bridge chip with the direction inputs
> tied to PB6 & PB7 (MISO & SCK respectively) as well as an on-board speaker
> tied from PB5 (MOSI) directly through the speaker to +V.
> 
> I noticed that when I tried to program the chip, the downloader software
> (built-in to BASCOM AVR could not determine what type of AVR chip I was
> programming.  When I removed the speaker and the FAN8200, it programmed
> the 2313 without any troubles.  After playing around with the prototype, I
> found that an LED appears to cause no trouble to the programming, and that
> if I run the speaker through a 360 ohm resister to +V, it seems to work.
> 
> My questions are these:
> 
> 1)  Are there any restrictions on use of the ISP pins for other than
> during programming?  In other words, what other things may/will cause the
> programmer to not find the AVR chip?
> 
> 2) Also, is this related specifically to the Sample Electronics
> programmer, or will I find the same limitations with one of the buffered
> ISP cables (6- or 10-pin)?
> 
> Thanks in advance,
> 
> Art
>