I recenlty tried using the P82B715 http://www.nxp.com/documents/data_sheet/P82B715.pdf
I2C extender chip to get cable lenghts of about 20 metres - worked great :-)
The problem I found was that the power drain for my battery operated device was just too high to be useful so wondering if anyone has experience of turning the power supply (in my case 3V3) to the I2C bus off between reading the sensors every 5 minutes? I guess I can use a transistor switched by a digital pin to do this as the power comsumption is more than 20mA but I thought I might ask for some advice before heading down a dark alley :-)
The questions I have are:
- Is the P82B715 the best way of extending cable length for a low power application?
- If a transistor routes sounds sensible would I be best switching the low side or high side and with which transistor to really keep power consumption to a minimum?
- If I turn the power to the I2C sensors off will I need to re-initialise them after powering on again or may I just continue to call for data as I would have done without powering off?
- Anyting else I should keep in mind when doing this?
- I'm guessing this has been written about somehwere but cannot find anything - anyone have a nice link?
Thanks for any thoughts - cheers