FMEA Step 3 — HW/Comm Interfaces

Hardware & communication interfaces

Interface-related failure modes, particularly with hardware and communications, are relatively common and relatively severe. List every hardware element the software must interface with, and any communications that affect it.

Inputs

Worked example — an intelligent thermostat

The software interfaces with the thermostat and is affected by the fan, furnace, heat exchanger, condenser coil, evaporator, combustion chamber, blower, ducts, air filters, and return/supply registers — six hardware components. It communicates over Wi-Fi. The software must detect major failures in any of these to maintain the required temperature.

Since there are six hardware components, the software generates six rows each for TL-EH-1, TL-EH-2, TL-EH-22, and TL-EH-23. One row each is generated for TL-EH-3 and TL-EH-4 (Wi-Fi down and undetected, or detected with the wrong response), and one for TL-EH-24 (Wi-Fi resuming without detection).

Failure mode ID

Description

Discussion / example

TL-EH-1

Software fails to detect a hardware fault

The furnace, heat exchanger, condenser, evaporator, combustion chamber, or blower fails and the software fails to detect it — six rows, one per component.

TL-EH-2

Software detects a hardware fault but executes the wrong behavior

Software detects the failure but displays a message to the user instead of sending a text — six rows, one per component.

TL-EH-3

Software fails to detect communication faults

The software fails to detect that Wi-Fi isn’t up.

TL-EH-4

Software detects communication faults but executes the wrong behavior

The software detects Wi-Fi is down and stops managing temperature entirely.

TL-EH-22

The software does not clear out faults that have been resolved

The software fails to detect when any of the six components has been fixed — six rows.

TL-EH-23

The software is overly sensitive to faults

The software falsely detects a failure in any of the six components — six rows.

TL-EH-24

The software fails to detect when communication has resumed after a loss

The software fails to detect that Wi-Fi is back up after being down.

Outputs

What gets auto-generated

Saving the hardware/comm interface table automatically generates the specific rows for TL-EH-1, TL-EH-2, TL-EH-3, TL-EH-4, TL-EH-22, TL-EH-23, and TL-EH-24.

Continue the FMEA workflow.

Next, assess the effects of each failure mode.

Assess Effects → ← Back to State Transitions