Finally, a little cable sanity. Let’s look at some cheap cables and some expensive cables and see exactly what these cables are capable of, and oh ya, trash a few of the broken ones.
As an Amazon Associate, at no additional cost to you I earn from qualifying purchases. If you don’t see Amazon product images on this page, or the ads seem incomplete, click here.
This first cable has the appearance of a good cable, but looks can be deceiving. Let’s jump right in and get into the details.
The setup for this test is easy. Plug one end of the cable into opposite sides of the device, then interpret the LEDs.
This first cable has GND and VBUS active on both ends of the cable, meaning the voltage bus is active and can make a complete circuit through ground. Assuming the cable ends still mate properly with your device, it can be used to power your phone or another USB-C device. The bad news is that the D- and D+ lines are active on only one end of the cable, meaning the cable cannot be used for data transfer. The cable may be defective or perhaps it operates this way by design.
1. USB Ports
Let’s look at the documentation. 
2. USB Cable Tester Pinouts
3. Battery Usage Instruction
4. Instructions for Use
5. PCB Design Principles
6. USB-Pinouts
7. Cable Lights Reference
Charge Only Cable
Charge and Data Cable
Charge and High Speed Data Cable
Comprehensive Charging, Data, Audio and Video
Lightning Cable
Reverse Side Silkscreen
Device Disclaimer
Type-A to Type-C Charging Cable, Fully Functional
Inexpensive cable for charging. For the purpose of charging, this cable is fully functional.
Type-A to Type-C Charging Cable, Fully Functional
Inexpensive cable for charging.
Type-A to MicroUSB Charging and Data Cable, Fully Functional
Basic cable that carries both power and data.
Type-C to MicroUSB Charging and Data Cable, Fully Functional
Quality cable that carries both power and data.
Type-C to Type-C Charging and Data Cable, Partially Functional
Note that while RX1 and TX1 are active for high speed data, D- and D+ are only active on one end of the cable. Data exchange may not work on older devices. GND and VBUS activity indicates that charging will work. This could be described as fully functional when used on a new device.
Type-A to Type-C Cable, Defective
The ground wire has gone bad.
Type-A to Type-C, Partially Functional
Note that while RX1 and TX1 are active for high speed data, D- and D+ are only active on one end of the cable. Data exchange may not work on older devices. GND and VBUS activity indicates that charging will work. This could be described as fully functional when used on a new device.
6 Type-A to MicroUSB
5 Type-A to MicroUSB
4 Type-A to Type-C
3 Type-A to Type-C, Partially Functional
D+ and D- Signals
The D+ and D- lights on a USB cable tester represent the differential signaling used in USB data transmission. USB employs differential signaling, which means it transmits two signals, D+ and D-, to convey data. The idea is that any electromagnetic interference will affect both D+ and D- similarly, allowing the noise to be canceled out by comparing the difference between these two signals. The receiver calculates the signal value (S) as the difference between D+ and D-. A positive S is interpreted as a digital 1, while a negative S is interpreted as a 0. By using differential signaling, USB achieves more reliable data transmission, especially in environments with potential electromagnetic interference.
In the context of a USB cable tester, the presence of these D+ and D- signals indicates that the USB 2.0 data lines are functioning correctly. The tester ensures that these wires are present and capable of handling USB data transfer up to at least USB 2.0 standards.
VBUS Signal
The VBUS light on a USB cable tester refers to the VBUS (Voltage Bus) wire in a USB cable. This wire is crucial because it carries the power supply voltage, which is essential for powering devices connected via USB. When the VBUS light is illuminated on the cable tester, it indicates that the VBUS and Ground (GND) wires are present and functioning correctly in the cable. These wires are necessary for providing power to a device through the USB connection.
In summary, the VBUS light on a USB cable tester is an indicator that the cable can properly supply power to a device, which is a fundamental aspect of USB functionality.
Issue when the D- and D+ are active on one side but not the other
What would it mean if the Pinrow A list for D- and D+ are active, yet the D- and D+ lights for Pinrow B are inactive?
If the D+ and D- lights are active on the Pinrow A but inactive on Pinrow B on a USB cable tester, it could indicate a possible issue with the wiring or connection of the D+ and D- lines in the cable. The D+ and D- represent the differential data lines used for USB 2.0 data transfer. These lines are crucial for the data communication aspect of USB technology, utilizing differential signaling to transmit data effectively and reduce the impact of electromagnetic interference.
The activation of these lights on one pin row but not the other could suggest that while one end of the cable is properly connected for USB 2.0 data transfer, the other end may have a fault or disconnection in the D+ or D- lines. This would mean the cable might not be capable of proper data transmission across both ends. It’s important to ensure that both D+ and D- are functioning correctly for the cable to support standard USB data transfer capabilities.
It’s also possible that this behavior could be due to the specific design or functionality of the cable, especially if it’s not a standard USB cable or has specific use-cases. If the cable is meant for charging only, for instance, the data lines might not be connected at all, which could cause such a result on the tester. However, for a typical USB data cable, both D+ and D- should be operational across the cable for proper functionality.
Finally, where to buy one
USB Cable Tester Board USB Cable Checker Data Wire with Acrylic Case Charging Test Data Line Type-C Micro Type A Type B
https://amzn.to/4awSEvz