OT:1-wire iButton protection

cstan_02 · Joined: 24 Jul 2005 Posts: 13

I have done this i-button reader of which the MCU is PIC16LF73 working with 3V. Now that's not at all the problem. The 1-wire data line is connected to the PIC pin directly with just a few ohms of resistance and a zener diode in parallel. The idea is to protect the PIC pin in case somebody tries to sabotage the system by applying high voltages on the 1-wire dataline in which case the PIC pin will be rendered useless. I'm afraid that my setup might not be fully protected. I've seen other circuits which use a schottky diode just in series with the dataline with the anode towards the PIC. And another I/o pin connected to the data line. Like this..

[INT0]
PIN_B0 Schottky 10-30 Ohm
[]PIC------------------|>|-------------/\/\/\/------------------|Reader data line
| |
| |
| |-----|<|---------------GND
PIN_B4----------| Zener Diode

This is the circuit that i'm talking about. How can i make it work through the firmware ? I'm using the CCS library for the touch device. Hope you guys can give me some hints. Thanks.

cstan_02 · Joined: 24 Jul 2005 Posts: 13

The picture that i draw does not appear exactly as i thought it would. Too bad that we can't upload pictures drectly. Sad

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

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cstan_02 · Joined: 24 Jul 2005 Posts: 13