Low power ibutton reader/writer

For orienteering, I'm considering building an ibutton device. The runners carry a button (4096 bit NVRAM) and click into each control point where their button gets the time at that control. The final control has RS232 or other external comms to a laptop which displays scores.

The control points need an battery powered MCU with piezo, LED and possibly EEPROM attached via the 1-wire bus to a button socket.

The question is, what's the minimum power required to run the control point? Is it possible (say with a small MSP-series) to idle the reader in the uA range so it doesn't need a switch?

Can you point me to any published low-power ibutton designs?

Clifford Heath.

Reply to
Clifford Heath
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Have you tried Maxim's web site?

A "standard" iButton reader should consume zero power until an ibutton is connected.

Reply to
JQP

The info at Maxim's site seemed flooded with appnotes showing PC-based readers, searches for "low power" turned up matches, but little relevant. Thanks anyhow, I'll dig into the data sheets.

Reply to
Clifford Heath

I have some PIC drivers for the Dallas/Maxim Touch memory stuff hidden away on CD. I am desperately searching for that CD now becasue I need one of the designs I backed up to it. Email me at: a dot pearson at optusnet dot com dot au and if I find it i will send the stuff to you. It has both loop driven CRC and table driven CRC routines. Trade off between speed and size...

Reply to
The real Andy

You can definitely do this with a PIC. I think the CCS C compiler comes with a library for reading/writing to iButtons. I have to ask where you are though? In the UK we are using two RF schemes one with Atmel RFID chips. If you're in the UK I'd be interested to talk about what you're doing - I know my club would be interested in cheap control-site equipment so it's not the end of the world if it gets stolen. Follow the links on our website and email sales.

Iain

Iain Tebbutt

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Reply to
Iain Tebbutt

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