add project README (hardware files are upcoming)
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purpose
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=======
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the name of the device says it all: "USB cable tester".
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it will test what kind of USB cable it is by checking which signals on the connectors are inter-connected by the cable.
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this helps identifying if a cable can transmit data or just deliver power.
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Apple's lightning connector is also supported although it is not strictly a USB connector.
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background
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----------
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micro-USB (USB micro-B) cables come with each new gadget to power it, or recharge its battery.
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these cable are not actual USB cables (which can transfer USB data), but only deliver power.
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the USB connectors are just used because it is convenient, and an ubiquitous power source.
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but you don't want to confuse them with actual USB cables supporting data transfer.
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sadly there are often no visible differences between a USB data cable and one just to deliver power.
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the USB cable tester is a tool to identify the USB cables.
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afterwards don't forget to label them afterwards to not get tricked in the future and stop wasting debugging time.
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since I would built a device to test USB cables, why stop at just testing if it has data lines.
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it can also test if the cable is shielded, supports USB 3.x, and even other USB connectors.
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this becomes even more interesting for USB-C cables since they have plenty of signals, some optional, and this is not identifiable just by looking at the cable.
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connectors
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the USB cable tester has the following connectors:
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- 2x USB type-A, supporting USB 3.x
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- 2x USB type-C, with all 24 pins
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- 1x USB type-B, supporting USB 3.x
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- 1x USB mini-B, USB 2.0 only
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- 1x USB micro-B, supporting USB 3.x
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- 1x Apple lightning
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these are the most commonly used USB connectors.
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the Apple lightning socket has been added because it is also a common charging connector, and there were enough free pins to also test this.
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there are two USB type-A connectors because some rare devices also use it (for example PCIe extension boards), although this should be a host-side connector.
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some Y-cables also use a second type-A host connector for devices requiring additional power.
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any combination of the connectors and signals can be tested (a list of know cables is built in the firmware).
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usage
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-----
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- plug all ends of the USB cable to test in the corresponding sockets
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- choose if the USB cable tester should be powered through its USB port or the battery using the switch
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- press on the RESET/START button
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- the result of the cable test will be displayed on the LCD and/or OLED screen
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if you connect the USB cable tester over USB (using the dedicated micro-B connector) to a computer, it will appear as USB device with a serial port.
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you can connect to it using a terminal (the baud rate does not matter) and have a console for more detailed tests and results.
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this is useful for cables with could not be identified, often because they are faulty.
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more tests are available on the serial prompt to identify the issues with the cable.
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just type "help" to get the available commands.
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limitations
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-----------
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the USB cable tester only tests if the signals are connected.
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it does not test:
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- the resistance of the cable (useful for cables used to delivery high currents)
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- if the shield is actually shielding the data cables or is just a wire (the impedance would need to be measured, which is complicated)
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- if the data line pairs are twisted (the impedance would need to be measured, which is complicated)
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I did not include the mini-A, micro-A, mini-AB, and micro-AB connectors since they are quite uncommon.
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firmware
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========
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binary
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------
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ready to flash firmware binaries are in the `release` folder
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source code
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-----------
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the firmware source code for this device is in the `firmware` folder.
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if you got this project using git, you need also check out this submodule using `git submodule init`.
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the source code in under GPL version 3 license.
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for more details check the `README` file on the `firmware` folder.
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this will also provide informations for firmware development.
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hardware
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========
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production
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the pdf schematic, board layer gerbers, and various other output files are in the `release` folder.
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design files
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------------
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the source design files are in the `hardware` folder.
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they are under the CERN Open Hardware Licence version 1.2.
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for more information check the `README` file on the `hardware` folder.
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