Diagnose a dock by symptom, using a table you build from the four negotiations

applied · 75 min · Objective 1.2

Task

Build the symptom-to-negotiation table for a USB-C connection, then test it against your own equipment and record which of the four capabilities each of your ports actually has. The table is what turns 'the dock does not work' into 'the port does not support DisplayPort Alternate Mode'.

Steps

  1. Write lab/dock/negotiations.csv with header capability,what_it_carries,symptom_if_absent,cheapest_test covering USB data, power delivery, DisplayPort Alternate Mode and Thunderbolt.
  2. Survey every USB-C port on every device you own into lab/dock/ports.csv with header device,port_id,data,power,video,thunderbolt,evidence. evidence names the specification page or the observation, not a guess.
  3. Write lab/dock/symptoms.csv with header symptom,negotiation_that_failed,first_test,second_test with at least six rows, including 'charges but no data' and 'data and no video'.
  4. Run at least three of your own first tests and record the outcome in lab/dock/observed.csv with header symptom,test,result,conclusion.
  5. Write lab/dock/limits.md stating, for your own machine, the maximum number of external displays the graphics can drive, and how you established it.

Verify

awk -F, 'NR>1 && NF>=4 {n++} END {print n" negotiation(s) described"}' lab/dock/negotiations.csv
awk -F, 'NR>1 && NF>=7 {n++} END {print n" port(s) surveyed"}' lab/dock/ports.csv
awk -F, 'NR>1 && $7!="" {n++} END {print n" port(s) with evidence"}' lab/dock/ports.csv
awk -F, 'NR>1 && NF>=4 {n++} END {print n" symptom(s) mapped"}' lab/dock/symptoms.csv
awk -F, 'NR>1 && NF>=4 {n++} END {print n" test(s) actually run"}' lab/dock/observed.csv
grep -c . lab/dock/limits.md

Four negotiations, at least two ports surveyed with evidence on every row, six or more symptoms mapped, three or more tests actually run, and a stated display limit. A ports table with an empty evidence column is a table of assumptions.

Notes

The evidence column is the point. 'It is USB-C so it does video' is the assumption that sells the wrong dock, and the manufacturer's specification page settles it in under a minute.

This is an independent study companion for CompTIA A+ Core 1 220-1201 and is not produced by or endorsed by CompTIA.