EivoTech Laptop & Mobile Repair Master Course
Mobile Repair Course — Part 7
USB-C, Lightning aur Advanced Charging Protocols Complete Mastery
Chapter 7: Connect → Detect → Negotiate → Power Transfer → Data Communication
Part 6 mein humne basic charging path cover kiya:
Charger → Cable → Port → Protection → Charging IC → Battery
Ab Part 7 mein hum ek level deeper jayenge.
Modern charging mein sirf voltage connect hona enough nahi.
USB-C system ko pehle ye decide karna hota hai:
Device connected hai?
Charger source hai ya sink?
Cable orientation kya hai?
Kitna current support hai?
PD supported hai?
Kaunsi voltage request karni hai?
Power safely switch ki ja sakti hai?
USB data kis orientation/path se route hogi?
Isliye USB-C ka advanced formula:
CONNECT → DETECT → NEGOTIATE → SWITCH → POWER → DATA
1. USB-C Kya Hai?
USB-C ek connector standard hai.
Important:
USB-C shape ka matlab automatically fast charging, USB4, Thunderbolt ya video output nahi hota.
Port features phone/platform-specific hote hain.
2. USB-C Connector ki Main Signal Groups
USB-C connector mein conceptually:
VBUS
GND
CC1
CC2
D+
D-
High-speed TX/RX pairs
SBU lines
hote hain.
3. VBUS
VBUS main USB power line hai.
Charging source se phone tak power carry karti hai.
Initial USB-C connection par safe default level commonly 5V-class hota hai.
4. GND
Current return path.
Connector shell/shield bhi grounding/EMI role play kar sakti hai.
5. CC1 aur CC2
CC:
Configuration Channel
USB-C ka bohat important part.
CC lines help karti hain:
Connection detect
Cable orientation
Source/sink role
Advertised current
USB PD communication
6. Orientation Detection
USB-C reversible hai.
Cable flip karne par:
CC1 aur CC2 ka role change ho sakta hai.
Isi liye one-orientation faults mein CC path important hota hai.
7. Source Kya Hai?
Power provide karne wala device:
Source
Example:
Wall charger.
Power bank output.
PC USB port.
8. Sink Kya Hai?
Power receive karne wala device:
Sink
Charging ke waqt phone commonly sink hota hai.
9. Dual-Role Device
Some phones:
Power receive bhi kar sakte hain.
Aur USB OTG/accessories ko power bhi provide kar sakte hain.
Is concept ko:
Dual-role power/data
ke context mein samjha ja sakta hai.
10. Rp aur Rd Concept
USB-C connection detection mein resistive signatures use hoti hain.
Simplified:
Source side
Rp-type advertisement.
Sink side
Rd-type termination.
Inko dekh kar devices role/connection identify karte hain.
11. Technician ke Liye Rp/Rd ka Meaning
Tumhe har resistor value memorize karne ki zaroorat nahi.
Main concept:
CC line par expected source/sink termination missing ho to charger VBUS ya PD negotiation start nahi kar sakta.
12. CC Line Open
Possible symptoms:
No charging.
One orientation only.
No VBUS.
No PD.
13. CC Line Short
Possible:
Charger detect fail.
VBUS enable na ho.
PD communication fail.
14. CC Line Leakage
Liquid/corrosion ki wajah se:
Line neither proper HIGH nor LOW.
Phone intermittent charging kar sakta hai.
15. CC ESD Protection
CC1/CC2 ke near ESD/protection component ho sakta hai.
Agar protection device short/leaky:
Port physically perfect hone ke bawajood charging fail.
16. USB-C Basic Connection Sequence
Simplified:
Cable inserted.
↓
CC termination detected.
↓
Source/sink roles confirmed.
↓
Orientation identified.
↓
Initial VBUS available.
↓
Optional PD negotiation.
↓
Requested power profile applied.
17. No CC Detection
Charger ko lag sakta hai:
No valid sink connected.
Result:
No proper power output.
18. Initial 5V
USB-C charging often initial default power state se start hoti hai.
Higher voltage use karne se pehle valid negotiation required ho sakti hai.
19. USB PD Kya Hai?
PD:
Power Delivery
USB-C devices ko digitally power contract negotiate karne deta hai.
20. PD Contract
Phone charger se request karta hai:
Supported voltage/current profile.
Charger accept kare:
Contract establish.
Then corresponding VBUS applied.
21. Example Concept
Charger offers:
5V
9V
Higher supported profiles.
Phone decides:
“Mujhe supported profile X chahiye.”
Then charger switch karta hai.
Exact profiles device-specific.
22. Phone Har Higher Voltage Request Nahi Karega
Request depends on:
Phone support.
Battery SOC.
Battery temperature.
System temperature.
Charging policy.
Cable capability.
23. PD Negotiation Fail
Phone may remain:
5V charging.
Slow charging.
Ya charge hi na kare depending fault.
24. PD Controller
Some phones have:
Dedicated PD controller.
Some integrate PD/CC logic into:
Charging IC.
PMIC.
USB interface IC.
25. PD Controller ke Main Functions
May manage:
CC detection.
PD communication.
Power role.
Requested voltage.
VBUS switch control.
Accessory detection.
26. PD Controller Input/Output Diagnosis
Think:
Power supply.
CC1/CC2.
Communication/control.
VBUS switch command.
SoC/charger communication.
27. PD Controller Power Missing
No PD behavior.
Possible even though physical port okay.
28. PD Controller Powered but CC Missing
Focus:
Connector.
ESD.
CC path.
29. CC Good but No Higher Voltage
Focus:
PD communication.
Phone request.
Charging policy.
Controller.
Cable/charger compatibility.
30. PPS Kya Hai?
PPS:
Programmable Power Supply
USB PD ka advanced feature.
Phone voltage/current ko finer steps mein dynamically request kar sakta hai.
31. PPS Ka Faida
Potentially:
Efficient charging.
Lower conversion losses.
Better thermal control.
Dynamic power adjustment.
32. PPS Charging Always Full Speed?
No.
Battery state aur temperature ke mutabiq charging current/voltage reduce ho sakti hai.
33. Battery Near Full
Even perfect PPS charger par:
Charging intentionally slow ho sakti hai.
Normal behavior.
34. Battery Hot
Fast charging disable/reduce ho sakti hai.
Thermal protection expected behavior.
35. Cable Capability
High-power charging ke liye correct cable important.
Wrong/poor cable:
PD profile limit.
Voltage drop.
Slow charging.
Reconnect loops.
36. E-Marker Concept
Certain higher-capability USB-C cables electronically identify capabilities.
Phone/charger ecosystem power decision mein cable capability matter kar sakti hai.
37. Technician Rule
Fast charging diagnose karte waqt:
Known-good charger + known-good compatible cable
mandatory baseline hai.
38. VBUS Switch
USB-C input power often protection/switch stage se guzarti hai.
May use:
MOSFET.
OVP.
Load switch.
Integrated power switch.
39. Why VBUS Switch?
Protect:
Phone from unsafe voltage.
Reverse current.
Short.
Wrong role.
Overvoltage.
40. VBUS Switch Diagnostic Formula
INPUT → CONTROL → OUTPUT
Agar input present:
Control check.
Then output.
41. VBUS Input Good, Output 0V
Possible:
Switch disabled.
Downstream short.
OVP fault.
Controller command missing.
42. VBUS Output Cycling
Possible:
Protection retry.
CC/PD instability.
Downstream overload.
43. Reverse Current Protection
Phone battery/system power ko accidentally charger side par uncontrolled backfeed nahi karna chahiye.
Power-path switches manage isolation.
44. OTG Mode
Phone accessory ko power provide kar sakta hai.
Then role changes:
Phone can act as source.
45. OTG Fault
Phone charging works.
But OTG USB drive not detected/powered.
Possible:
Role detection.
VBUS source switch.
USB data path.
Software.
46. Charging Works ≠ OTG Works
Charging sink path aur OTG source path partially separate ho sakte hain.
47. Data Role
USB-C power role aur data role related but identical nahi.
A device:
Power sink.
Data host/device
different combinations support kar sakta hai.
48. USB2 D+ / D-
USB2 compatibility ke liye D+/D- lines remain important.
49. USB-C mein D+/D- Duplicate Contacts
Connector reversibility ki wajah se physical duplicates route kiye ja sakte hain.
Phone design them internally combine/route karta hai.
50. D+ / D- Fault
Phone charges but:
PC no detect.
MTP fail.
ADB/USB communication fail.
Older fast-charge detection affect ho sakti hai.
51. High-Speed Differential Pairs
USB 3.x high-speed communication ke liye:
TX/RX differential pairs.
Routing bohat sensitive hoti hai.
52. Differential Pair Meaning
Do matched complementary signals.
Need controlled:
Impedance.
Length.
Routing.
53. Long Jumper Problem
Random long jumper:
High-speed signal degrade.
Data instability.
No SuperSpeed connection.
54. USB Mux
Because USB-C reversible hai:
High-speed lanes correct orientation mein route karne ke liye mux use ho sakta hai.
55. Mux Fault Symptoms
USB2 works.
Fast charging works.
But:
High-speed data fails.
Video output fails.
One orientation high-speed function fails.
56. Retimer / Redriver
Some advanced devices high-speed signals ko condition/amplify karne ke liye retimer/redriver use karte hain.
More common high-performance USB-C platforms.
57. Retimer Fault
May affect:
High-speed USB.
Display output.
One orientation.
But basic charging still work kar sakti hai.
58. SBU Lines
Sideband Use lines.
Can support alternate-mode/accessory functions.
Not standard charging power rails.
59. Alternate Mode
USB-C can carry non-USB functions such as display output on supported devices.
Physical Type-C port alone Alt Mode guarantee nahi.
60. Display Alt Mode Fault
Charging works.
USB2 works.
External display nahi.
Focus:
Mux.
SBU/high-speed route.
Display-mode controller.
Not battery.
61. USB-C Complete Signal Separation
Always separate:
Power
VBUS.
Configuration
CC1/CC2.
USB2 Data
D+/D-.
High-Speed Data
TX/RX pairs.
Sideband
SBU.
62. One Function Working Doesn't Prove Others
Example:
Charging ✅
USB2 data ✅
Video ❌
Different path.
63. One Orientation Charging Only
Most likely area:
CC/port/protection.
64. One Orientation USB3 Only
Could be:
Mux/high-speed lane.
Port contact.
65. Both Orientations Charge, No PC Data
Focus D+/D-/data route.
66. PC Data Works, No Fast Charge
Focus CC/PD/protocol/battery condition.
67. Fast Charge Works, No OTG
Focus power/data role source function.
68. USB-C Port Physical Damage
Common:
Bent contacts.
Corrosion.
Loose shell.
Cracked anchors.
Internal contact wear.
69. Port Mechanical Anchors
Anchors support physical strength.
Weak anchors:
Port moves.
Solder pads crack.
Intermittent faults.
70. Port Replacement Quality Check
After legitimate service:
Inspect:
Alignment.
No bridges.
VBUS-GND no short.
CC paths.
Data.
Both orientations.
Mechanical stability.
71. Charging Sub-Board USB-C
If Type-C is on sub-board:
Before main-board IC diagnosis:
Try known-good sub-board/flex where appropriate.
72. Main-Board Type-C
Some devices port directly main board par.
Then local port/protection work directly board par.
73. Liquid Damage on Type-C
Common affected lines:
CC1.
CC2.
VBUS.
D+.
D-.
Corrosion can create leakage.
74. Corrosion and PD
CC line leakage can make charger think invalid connection.
Phone may:
Slow charge.
Reconnect.
Not charge.
75. VBUS Corrosion
High-resistance contact:
Voltage sag under load.
Heat.
Intermittent connection.
76. PD Negotiation Diagnostic Thinking
Don't ask only:
“9V aa rahi hai?”
Ask:
Phone ne higher voltage request ki bhi?
77. If Phone Doesn't Request Higher Voltage
Possible:
Battery near full.
Battery hot.
PD disabled by software/policy.
CC/PD fault.
Unsupported charger/cable.
78. If Phone Requests but Charger Doesn't Switch
Possible:
Charger.
Cable.
Communication instability.
79. If VBUS Switches Then Falls Back
Could indicate:
Phone rejects/loses contract.
Protection.
Load/current issue.
Thermal/policy.
80. PD Meter as Diagnostic Clue
A USB power meter can help observe:
Initial voltage.
Negotiated voltage.
Current behavior.
But meter itself can alter compatibility in some setups.
Use it as supporting evidence.
81. Current Alone Not Enough
2A current doesn't tell exact circuit health.
Need:
Voltage.
Protocol.
Battery state.
Temperature.
82. Lightning Connector Kya Hai?
Lightning Apple ka proprietary reversible connector hai, used on many older iPhone generations.
Newer iPhone generations use USB-C.
83. Lightning Reversible Design
Connector both orientations mein insert ho sakta hai.
Phone/accessory internal logic correct contact mapping handle karti hai.
84. Lightning Basic Functions
Conceptually carries:
Power.
Ground.
Data/accessory communication.
Detection/control.
Exact pin assignment/orientation handling device-specific.
85. Lightning Charging Path
Simplified:
Charger
↓
Cable
↓
Lightning port
↓
Protection/detection
↓
USB/charging interface
↓
Charging/power management
↓
Battery.
86. iPhone Charging Logic
Apple devices cable/accessory identification and USB charging communication use karte hain.
Exact IC names/model architecture later iPhone section mein detail cover honge.
87. Lightning Cable Quality
Non-compliant/damaged cable:
Accessory warning.
No charging.
Intermittent charging.
No data.
88. Lightning Port Fault
Possible:
No charging.
Charge at angle.
One orientation issue.
No PC detection.
Accessory not supported message.
89. Lightning Port Contamination
Lint/debris commonly cable ko fully seat hone se rokti hai.
Physical inspection important.
90. Lightning Data vs Power
Same USB principle:
Power path and data/detection path separate ho sakte hain.
91. iPhone Charges but Computer Doesn't Detect
Focus:
Port/data/interface.
Not battery first.
92. Computer Detects but No Proper Charging
Focus:
Charging/power path.
Battery/temp.
Input management.
93. Lightning Port Flex
Some iPhones charging port is part of a flex assembly.
This assembly can include other functions depending model.
Known-good compatible assembly comparison useful.
94. Port Flex Fault Can Mimic Board Fault
Before major board IC conclusion:
Inspect/test charging flex.
95. Authentication Concept
Some accessory ecosystems use legitimate identification/authentication mechanisms.
Repair goal is to restore normal supported communication, not bypass device security.
96. Lightning Fast Charging
Supported iPhones can use USB-PD on charger side with suitable cable/connector setup.
Phone still controls accepted power.
97. USB-C iPhone
USB-C iPhones follow USB-C power/data architecture, though Apple-specific board implementation still varies.
98. Lightning vs USB-C Diagnosis Similarity
Both need:
Physical port.
Power path.
Detection/communication.
Data.
Charging management.
99. Main Difference
USB-C:
Standardized CC/PD architecture.
Lightning:
Apple proprietary connector/interface architecture.
100. Advanced No-Charge Workflow
Step 1 — External
Known-good charger.
Known-good cable.
101. Step 2 — Physical Port
Inspect connector.
102. Step 3 — Connection Detection
USB-C:
CC1/CC2.
Lightning:
Relevant port/interface detection.
103. Step 4 — Input Power
VBUS/power reaches board?
104. Step 5 — Protection
OVP/switch output?
105. Step 6 — Charger Controller
Input/control valid?
106. Step 7 — Battery
Detected?
Temperature valid?
Health okay?
107. Step 8 — Fast-Charge Protocol
Negotiation occurring?
108. Step 9 — Actual Charging
Battery current/SOC changes?
109. USB-C One Orientation Case
Known-good cable.
Orientation A:
5V + PD works.
Orientation B:
No VBUS.
Likely:
CC/port path.
110. USB-C 5V Only Case
Both orientations work.
Initial 5V stable.
No PD higher profile.
Battery cool, low SOC.
Known-good PD charger/cable.
Direction:
CC/PD control path.
111. USB-C Fast Charge But No Data
PD works.
Battery charges fast.
PC no detect.
Direction:
D+/D- or USB data path.
112. USB-C USB2 Works, USB3 Doesn't
Focus:
High-speed lanes.
Mux.
Connector.
Retimer if present.
113. USB-C OTG Dead
Charging okay.
Data to PC okay.
OTG accessory unpowered.
Direction:
Power-role/source-VBUS path.
114. USB-C Reconnect Loop
Possible:
CC unstable.
Port contact.
VBUS switch.
Cable.
Protection.
115. Lightning Charges One Orientation Only
Strong physical port/cable/interface clue.
Known-good cable comparison first.
116. Lightning Charging but No Data
Port/data/interface path.
117. Lightning No Charge but Wireless Works
Battery/main system likely substantially okay.
Focus wired charging path.
118. Wireless + Wired Both Fail
Then common downstream:
Battery.
Charging management.
Thermal/data.
becomes more relevant.
119. Fast Charging Thermal Example
Phone at 20% battery.
PD starts.
Phone becomes warm.
Charging power decreases.
Could be normal thermal regulation.
120. Don't Force Higher Voltage
Never bypass negotiation and directly feed higher USB-PD voltage into phone VBUS expecting faster charging.
Power contracts/protection exist for a reason.
121. Don't Bridge CC Lines
CC1/CC2 are logic/configuration signals.
Random bridging can damage port/controller.
122. Don't Apply Battery Voltage to CC/Data
CC, D+, D-, SBU are signal lines.
Not power rails.
123. Don't Bypass OVP
If OVP blocks power:
Find why.
Permanent bridge removes protection.
124. Don't Bypass Current Sense
Charging safety/control depends on correct sensing.
125. USB-C Safe Diagnostic Formula
PORT → CC → INITIAL VBUS → PD → VBUS SWITCH → CHARGER IC → BATTERY
126. USB Data Formula
PORT → ESD → D+/D- / HIGH-SPEED → MUX → PHY → SoC
127. Lightning Diagnostic Formula
CABLE → PORT/FLEX → DETECTION/DATA → INPUT POWER → CHARGING CONTROL → BATTERY
128. Case Study 1 — USB-C Dead Both Sides
No charging either orientation.
Known-good cable/charger.
No VBUS.
Both CC paths abnormal.
Port corrosion visible.
Diagnosis direction:
Port/CC area.
129. Case Study 2 — One Orientation
CC1 behaves normally.
CC2 path open.
Result:
One orientation fails.
130. Case Study 3 — PD Missing
Initial VBUS normal.
CC detection okay enough for connection.
PD communication never progresses.
Direction:
PD controller/communication/policy.
131. Case Study 4 — PD Negotiates then Drops
VBUS increases briefly.
Then returns to default.
Check:
Battery/system load.
Protection.
Thermal.
Contract stability.
132. Case Study 5 — Charge Fine, PC Dead
D+ line open after ESD array.
Diagnosis:
USB2 data path.
133. Case Study 6 — USB3 Dead Only
USB2 works.
PD works.
High-speed mux path damaged.
Diagnosis:
High-speed path.
134. Case Study 7 — Lightning No Charge after Drop
Wireless charging works.
Port flex physically damaged.
Direction:
Lightning port/flex.
135. Case Study 8 — Lightning Charge Intermittent
Cable must be held at angle.
Known-good cable same.
Port contaminated/damaged.
Direction:
Physical connector.
136. Case Study 9 — No Fast Charge Due Battery Temp
Port/PD all normal.
Battery temperature reading invalid.
Phone stays slow/no charge.
Direction:
Battery temperature sensing.
137. Case Study 10 — Charging Works Only Screen Off
No PD negotiation.
Low-power default charging only.
System consumes almost all incoming power while screen on.
Direction:
Fast-charge negotiation/input capability.
138. USB-C Advanced Worksheet
Phone Model: __________
Port Type: USB-C
Known-Good Charger: __________
Known-Good Cable: __________
Orientation A: __________
Orientation B: __________
CC1 Behavior: __________
CC2 Behavior: __________
Initial VBUS: __________
PD Negotiation: __________
Negotiated VBUS: __________
VBUS Switch Input: __________
VBUS Switch Output: __________
Battery Detected: __________
Battery Temp: __________
USB2 Data: __________
High-Speed Data: __________
OTG: __________
First Missing Stage: __________
Final Fault Area: __________
139. Lightning Worksheet
iPhone Model: __________
Known-Good Cable: __________
Port Condition: __________
Both Orientations: __________
Input Power Reaches Board: __________
Computer Detection: __________
Charging Symbol: __________
Actual Charging: __________
Wireless Charging: __________
Battery Temp/Data: __________
Port Flex Known-Good Test: __________
Final Fault Area: __________
140. Advanced Charging Fault Categories
Category A
No physical connection detection.
Category B
Connection detected, no VBUS.
Category C
5V works, no fast charge.
Category D
Fast charge negotiates but unstable.
Category E
Power works, data fails.
Category F
Data works, charging fails.
Category G
One orientation fails.
Category H
OTG/source mode fails.
141. Why Categories Matter?
Har category ka different starting point hota hai.
Example:
One orientation:
CC/connector.
5V only:
PD.
Charging but no data:
D+/D-.
142. Common Beginner Mistake 1
USB-C no charge → charging IC replace.
143. Common Beginner Mistake 2
CC1/CC2 ignore.
144. Common Beginner Mistake 3
5V present → PD okay assume.
145. Common Beginner Mistake 4
No fast charge near 100% battery ko fault samajhna.
146. Common Beginner Mistake 5
One orientation fault mein PMIC replace.
147. Common Beginner Mistake 6
D+/D- ko CC lines samajhna.
148. Common Beginner Mistake 7
High-speed pair ko random wire se repair.
149. Common Beginner Mistake 8
OTG fault ko charging fault samajhna.
150. Common Beginner Mistake 9
Lightning no charge par port flex test skip.
151. Common Beginner Mistake 10
Protection IC bypass.
152. USB-C Golden Rules
1. USB-C connector reversible hai, isliye CC1/CC2 orientation diagnosis mein critical hain.
2. Source power deta hai, sink power leta hai.
3. Rp/Rd connection/role identification ka part hain.
4. Initial VBUS aur negotiated PD power alag stages hain.
5. 5V present hona PD success ka proof nahi.
6. PPS dynamically adjustable PD charging hai.
7. Power, USB2 data aur high-speed lanes separate paths hain.
8. One orientation fault mein connector/CC path first.
9. PD higher voltage ko manually force mat karo.
10. OVP/current-sense protections bypass mat karo.
153. Lightning Golden Rules
1. Lightning reversible proprietary interface hai.
2. Cable/port/flex ko motherboard IC se pehle rule out karo.
3. Charging aur data paths separately fail ho sakte hain.
4. Wireless charging working ho to wired-input path stronger suspect hota hai.
5. Supported charging/authentication environment ko restore karo, bypass nahi.
154. Part 7 Quick Revision
CC1 / CC2
USB-C connection, orientation aur negotiation signals.
Source
Power provider.
Sink
Power receiver.
Rp
Source-side connection/current advertisement concept.
Rd
Sink-side connection signature concept.
PD
USB Power Delivery.
PPS
Programmable Power Supply.
VBUS Switch
Input power control/protection stage.
Mux
Orientation/data-path routing IC.
Retimer
High-speed signal conditioning device.
SBU
USB-C sideband signal lines.
Lightning
Apple proprietary reversible connector used on many older iPhones.
155. Part 7 ka Sabse Important Lesson
USB-C ko sirf:
“Charging Port”
mat samjho.
Ye actually multiple systems ka connector hai:
POWER + CONFIGURATION + NEGOTIATION + DATA + OPTIONAL VIDEO/ACCESSORY FUNCTIONS
USB-C charging ka complete flow:
CONNECT → CC DETECT → INITIAL VBUS → PD NEGOTIATE → VBUS SWITCH → CHARGER IC → BATTERY
Aur troubleshooting mein:
One side works? → CC/Port
Only 5V? → PD negotiation
Charges but no PC? → Data path
USB2 works but high-speed fails? → Mux/high-speed path
OTG fails? → Source-role path
Isi tarah Lightning mein:
PORT/FLEX → DETECTION/DATA → CHARGING CONTROL → BATTERY
ko separately diagnose karo.
Professional technician ka goal voltage ko force karna nahi, balki connection aur negotiation chain mein first missing stage identify karna hai.
Mobile Repair Course — Part 7 Complete
Next — Mobile Part 8: Smartphone Display + Touch Circuit Complete Mastery
Part 8 mein hum detail se cover karenge:
LCD vs OLED.
Display connector.
Display power rails.
Display bias voltages.
Backlight circuit.
OLED power architecture.
MIPI DSI.
Display reset.
Display enable.
Touch controller.
Touch I2C/SPI.
Touch reset/interrupt.
No display vs no boot.
White screen/lines/flicker.
No backlight.
Touch dead.
Ghost touch.
Known-good screen diagnosis.
Connector/pad faults.
Aur complete:
PHONE BOOT → DISPLAY POWER → RESET → DATA → IMAGE → TOUCH
diagnostic workflow.
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