Self-detect Pinout Connection


I am working in a project where there is a device and some sort of a “dock station” where the unit rest and charges, it can be placed in any direction, however, the “engaging” positions are limited to 4, let’s call it North, South, Est and West, with no particular visual feedback or mechanical limitation on how the user can leave the unit in the dock, actually it is a requirement to be in any way. The dock station needs to have connection to the device with 4 pins, positive, negative, detection pin (probably just a resistance to Gnd) and a digital output (a physical button).

For a few reasons inductive charging and ring tracks (like slip-rings) are not possible, so we ended up in the concept with 4 spring pins in each corner and 1 in the center.

With that approach, do you see a way to have some sort of pinout detection? My first idea was to have gnd in the center and because N and S, W and E are going to be always pair connections have two bridge rectifiers so one will be powering the circuit once mated and a mosfet arrangement to switch the other bridge input to a different circuitry for the detect and digital input.

The problem with that approach is that pins are going to be energized all the time (paper clips, coins, etc), maybe a reed switch to enable power output and a small magnet in the device can do the trick.

What do you think? thanks

How about a two-wire connection and using transformer/capacitively coupled connection to send presence and button-press pulses? Use, say, a 40 kHz pulse-train and use the pulse width to indicate the digital bit?

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Maybe don’t use power rails. Pulse the voltage on the 4 pins, keeping center pin GND. The pulse can be used as TX. Measure current to detect button depressed

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Hi ToyBuilder and kvk, thanks
both are good ideas, not sure how to implement, I’ll explore more.

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Or eliminate the need for detection - offset the corner pins slightly and put four contacts in each corner of the device (16 total) Only one contact is used in each corner, but four are available to support each orientation and function.