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What is inside the Spike Ultrasonic Sensor 45604?

Element photo

Pictures of Top&Bottom PCB-Assembly would be helpful.

PoweredUp Cable and Connector use 6-Pin, but why is there used 8-Pin connector inside "black-and-white" Module connection? Are these 2 additional pins in use? What is their function?

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The back of this sensor unscrews. The back breaks out the 6-pin cable into an 8-pin connector:

Inside of back

The order of the connections for the pins in that picture from left to right are:

 6    5    4    3    x    x    2    1
ID2  ID1  VCC  GND   x    x   M2   M1

The primary sensor can be pulled out of the front of the part:

Sensor Front

We can then remove the shroud around the sensor to reveal the front side of the PCB:

PCB Front

The largest chip on the front side is an STM8S105K6.

Here's the PCB from the back:

PCB Back

The largest chip on the back is a HEF4049BT hex inverting buffer.

I don't have any insight into why an 8-pin connector is used internally when there are only 6 conductors in the wire, but I did confirm electrically that 6 of the 8 pins are connected to the 6 conductors in the wire.

There are 3rd-party breakout boards that can make the connections from the back of the ultrasonic sensor available for advanced usage:

Breakout board

A header (or individual wires) of appropriate size can also be inserted directly into the back of the sensor without a specialized board, but the pitch is smaller (0.050" or 1.27mm) than what is typically used by hobbyists.

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    I'm confused/intrigued by community.legoeducation.com/blogs/31/220 , about "the back of the [distance] sensor can be removed and the cable detached, effectively becoming a LEGO Power Functions 2.0 (LPF2) breakout cable"
    – IvanSanchez
    Commented Jan 6 at 15:13
  • @IvanSanchez Thanks for sharing that! I've added info about that breakout board to the answer.
    – jncraton ♦
    Commented Jan 6 at 15:27
  • My guess for the 8-pin mystery is that it's a fail-safe mechanism. AFAICS, pins 3 and 4 are +VCC and GND, whereas 5 and 6 are not connected to anything. Since the connector is symmetrical, one could plug a connector rotated 180° - when doing so, +VCC and GND are connected to nothing, i.e. a fail-safe state. If this fail-safe was not in place, it could be possible to connect +VCC to GND and GND to +VCC (or some other weird combination) and potentially damage the circuits.
    – IvanSanchez
    Commented Jan 7 at 4:35
  • Thanks for your quick answer Can you confirm uC : STM8S105K6 in QFP on Top-Side ? What is the SO16 Chip on Bottom Side ? An Hex-CMOS Inverter as 9V Driver would be in SO14, so would not fit ... Jo
    – user22626
    Commented Jan 7 at 15:53
  • @user22626 I've added the info for those chips.
    – jncraton ♦
    Commented Jan 9 at 0:44

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