AVR-Chat

John Samperi wrote:
> At 09:52 AM 23/10/2007, you wrote:
>> I need for this thing to start up whenever the locomotive sees power
> 
> Enable the Brown Out Detector, this will give you reliable reset at
> power up. 
> 
> The point I'm trying to make is that, if you have a track running
> from the reset line, say to the ISP connector, then you have a small
> antenna connected to the reset line. With a high resistance in the
> reset line like the internal pull up, one is more likely to pick up
> rubbish that COULD give you spurious resets. A cap on the reset line
> will help with this as well as giving you another reset at power up. 
> 
> However you SHOULD use the internal BOD at least for better
> reliability. 
> 
> I'm fortunate enough that my projects have never been that packed or
> price sensitive that I could not put a cap and resistor in the reset
> line.  
> 
> Try it without see what happens, I may just be a panic merchant :-)
> 

The earlier Tinys (11,13,15) did require an external 10K pullup on the
reset pin or they did not start up at all (did not need an RC though).
But the newer ones don't need anything. In fact I have found that adding
an RC can actually make the startup less reliable in an intermittent
power situation. I don't think I was using the Brown Out Detector when I
had this problem however, I agree with John that you should enable that.

-- 
Tim Mitchell
tim@sabretechnology.co.uk http://www.sabretechnology.co.uk
Sabre Technology (Hull) Ltd, 3a Newlands Science Park, Hull HU6 7TQ
Registered in England and Wales no.3131504
t:01482 801003 f:01482 801078