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Topic: Hardware robustness... (ADC & RESET)... (Read 10 times) previous topic - next topic

Nicko

Hi,

I work in a high-EMI environment. A couple of small changes to the standard Arduinos would ease matters for those like myself:

1. Add in a low pass filter for the AVCC pin - a simple LC filter (15uH, 10nF) as recommended by Atmel - this will also enable more accurate ADC readings...

2. read AVR040 & AVR042 - it's not commonly known that the /RESET pins on most AVRs is not ESD-protected in the same way as all other I/O pins - its almost impossible to find this out in the data sheets - its very obtuse indeed. A small diode (1N4148) with a 4k7 resistor to VCC, and a 4n7 cap to ground would help greatly (assuming you're not using HV programming). In addition, leaving space for a small zener between GND & /RESET would allow it to be easily added in very high noise environments.

Probably only a few cents to add, but these are simple changes that are recommended by Atmel that would, IMHO, greatly improve the robustness of these boards.

Cheers

Nick

jluciani

Both of these changes are implemented on all of my boards.
http://www.wiblocks.com

1. I use a 10uH, 0.1uF low pass filter.
2. For the reset I have a 1N4148 from the reset pin to Vcc. I also include
   a position of a 0.1uF cap from /RESET to GND. (NB If you use the
   0.1uF from /RESET to GND the /RTS on close reset will not work
   reliably).

(* jcl *)

retrolefty

Quote
it's not commonly known that the /RESET pins on most AVRs is not ESD-protected in the same way as all other I/O pins - its almost impossible to find this out in the data sheets - its very obtuse indeed.


I believe that is so it can be set-up for high voltage programming where (I think) +12vdc is wired to the reset pin. Perhaps the datasheet section covering HV programming might explain the reset pin functions better. Obviously the normal clamping diodes from Vcc to pin wouldn't work for this pin.

Nicko

Quote
I believe that is so it can be set-up for high voltage programming where (I think) +12vdc is wired to the reset pin. Perhaps the datasheet section covering HV programming might explain the reset pin functions better. Obviously the normal clamping diodes from Vcc to pin wouldn't work for this pin.
As I stated in point 2 of my OP, HV programming precludes the use of the full ESD protection, but Arduinos don't use that so can take advantage of the optional additional protection. Even if empty  pads were left for optinal extra components, that'd be good and at no extra cost to the dev board.

Cheers

Nick

laxman

Hi,

I work in a high-EMI environment.its very....good programming

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