1-wiremicrocontroller
I've seen Dallas' 1-wire sensors, they look great. But, I'd like to make some custom 1-wire slaves which can be parasitically powered (just ground + data).
Can anyone recommend a low power microcontroller which is suitable for this?
Does anyone have a sample circuit for how I would power an MCU from the 1-wire bus?
What the schematic does not show is the huge common mode 60Hz hum and how the grounds are interconnected with proximity to AC lines & power line transients.
Your example is a good example of how not to interface long wires.
May I suggest in future;
Since many options are not avail. Do these;
With this solution, the switch circuit impedance will low impedance on closure and low impedance with elect-cap across switch when open. CM hum will be absorbed and differential RF noise is suppressed.
-pullup to same supply voltage as uC with good RF cap across chip.
For anything to run linux, it can't be a simple 8 or 16 bit microocntroller. Your best bet is an ARM based system, in particular Cortex A8 or A9. Basically aside from the raspberry pi you've got beagle board, beagle bone, panda board and a few similar other boards.
I'm not sure there is a custom apps processor module available in general. If you're an OEM then of course you can find something.
If you are willing to build your own solution you can make it very small.
Best Answer
The one wire bus has the bus passively (i.e. with a resistor) pulled up in the system, and devices communicate on the bus by pulling the bus down. What I would do if I wanted to pull power from the bus is:
You should use a Schottky diode, to minimize the voltage drop. The diode/capacitor combination should make it so that communication can take place (i.e. grounding the bus periodically) without shutting down the MCU. Putting the capacitor after the diode will keep the transitions on the bus data sharp, while keeping the decay of power (voltage) to your MCU gradual. The lower power the device you use is the better to minimize drain on your capacitor, but pretty much any MCU will probably work for you. My preference is Atmel's AVRs, but TI MSP430s and Microchip's PICs are also good candidates for low power consumption.