2023-04-09 - RCA for Signal Integrity

Owned by Daniel Puratich, created
Last updated: 2023-04-13
2 min read

Update the title following the format: Jan 01, 2023 - RCA Name

1 Incident overview | 2  Executive summary | 3  Incident timeline | 4  Postmortem report | 5  Recommendations for future

Incident overview

Postmortem owner

@Daniel Puratich

Airframe

 

Related incidents

 

Incident date

Feb 13, 2023

Approx. Damage Costs

 

Report Date

Feb 13, 2023

 Executive summary

https://discord.com/channels/776618956638388305/930937310340583494/1095099811889430590

unfortunatrly busy with finals currently, but here it is from a high level. Signal integrity issues on dshot were preventing us from transitionning. We suspect this is bc ground connection on pwm wire was disconnected as this is the only way we could recreate the issue on the ground. See scope shots in flight test media folder to coroboarate this. Dshot has a CRC so it requires a lot of bad data before it quits. Even with ground connected the signal was ugly so we’ll need to rectify that. Using twisted pwm wires is a first step. Next is securing conections to pizhawk and esc. Finally a harness without the floating power conductor on the pwm wire would be nice, but we’d have to custom make that. Further it was determined, by some deductive reasonning, that the cause of our servos twitching is also signal integrity. We investigated briefly using CAN repeaters, but this is a lot of added complexity, maybe for next competition. Also see that linked discord convo for more context.

 

 Incident timeline

Describe (approximate) timelines, cross-correlate with telemetry/video recordings/etc if any.

 Postmortem report

Instructions

Report

Instructions

Report

 Leadup

List the sequence of events that led to the incident.

 

 Fault

Describe what didn't work as expected. If available, include relevant data visualizations.

 

 Detection

Report when the team detected the incident and how they knew it was happening. Describe how the team could've improved time to detection.

 

 Response

Report who responded to the incident and describe what they did at what times. Include any delays or obstacles to responding.

 

 Recovery

Report how the user impact was mitigated and when the incident was deemed resolved. Describe how the team could've improved time to mitigation.

 

Five whys root cause identification

Run a 5-whys analysis to understand the true causes of the incident.

 

Related records

Check if any past incidents could've had the same root cause. Note what mitigation was attempted in those incidents and ask why this incident occurred again.

 

 Lessons learned

Describe what you learned, what went well, and how you can improve.

 

 Recommendations for future

Actionable Recommendation

Reasoning

Actionable Recommendation

Reasoning