Download pin

[f2cf1g]

Is it acceptable/safe to disable the download input pin by connecting it directly to earth rather than through a resistor? The reason for doing this is to minimise component count. The chip will be programmed out of circuit and the code will have been debugged beforehand.

 

[JimPerry]

Not a good idea - can short pin to ground from Vcc if EVER set as an output - resulting in magic smoke

 

[AllyCat]

Hi,

The Programming Serial Input is "Input Only" so it can never be set as an output (at least using normal PICaxe Basic commands).

Therefore, it is "permissible" to connect it directly to earth, but personally I would always put a resistor to ground, just in case I later decide/discover that I need a programming (or particularly debugging) facility on the board.

Cheers, Alan.

 

[f2cf1g]

Thanks guys. The idea is to do away with the need for a board altogether. It's for use in a radio controlled dethermaliser setup, nestled between various other bits of electronics, the mounting will probably be servo tape. The functionality is simple so hopefully there will only ever be one version (hope, hope).
Cheers, Roy

 

[premelec]

My curiosity having flown some: Is a dethermaliser the same as a spoiler?

 

[f2cf1g]

Similar function, different implementation. It usually takes the form of a tip up tail, to stall the wing.

 

[premelec]

Thanks - I was taught the fastest altitude loss in small plane was to spin and of course recover before ground contact...

 

[Greyling]

I always thought it was a good idea to use the resistor in case of static discharges or nearby lightning strikes that can effect the ground.