72 lines
3.7 KiB
Markdown
72 lines
3.7 KiB
Markdown
The USB micro-B and C cable tester identifies capabilities supported by USB cables and deduces it's purpose.
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It helps figuring out if a USB cable is for charging or to transfer data, and at which speed.
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It supports type A to micro-B, A to C, and C to C USB cables.
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usage
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=====
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- ensure the tester has a non-empty battery in the CR2032/2025, or is externally powered through the USB power port
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- plug one end of the cable in one of the host ports
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- plug the other end of the cable in one of the devices ports
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- the tester will identify the cable's capabilities, on the left side
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- the tester will then show the cable's purpose, on the right side
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To understand further the capabilities and purpose of a cable, I recommend reading the USB specification, mainly the one for the [type-C connector](https://www.usb.org/document-library/usb-type-cr-cable-and-connector-specification-release-23).
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design choice
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=============
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features
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--------
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do:
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- USB micro-B: still wide-spread and popular for charging devices
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- USB type-A: still the de-facto host plug
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- USB type-C: becoming the standard for battery operated devices
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- C to C: often used for high power charging of phones and laptops
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- battery operated: it's a very simple device, and this avoids needing to require external power
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- power port: in case you have no battery or it runs out
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- USB 3.0: because it is hard to identify if C-C cable support SuperSpeed
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- purpose: deduce from capabilities
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don't:
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- small: no need to build it as compact as possible
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- A or micro-B 3.0: the connectors that support it are obvious, and it's rare they are used for anything else than Super-Speed transfer (plus they are less common or problematic)
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- Power Delivery capabilities: this requires complex host software communicating with the eMarker chip in the cable
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- OTG: even if detecting this functionality is easy, micro-B OTG adapters are not popular anymore
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- impedance: only the presence of wires is tester, not their impedance
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mode of operation
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-----------------
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Most of the tests just verify if the wires corresponding to capabilities are present in the cable.
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Some additional tests verify the resistances in the plugs.
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For more details, check the schematic, and refer to [type-C specification](https://www.usb.org/document-library/usb-type-cr-cable-and-connector-specification-release-23).
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The left side identifies the capabilities.
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Based on that, a micro-controller (MCU) with map the combination into a purpose on the right side.
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The left side if independent of the MCU and right side.
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limitation
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----------
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The tester does not:
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- verify the resistance of wires, particularly the power ones
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- verify the impedance of wires, particularly the differential ones
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- verify if the shield(s) is more than just a wire
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- read out capabilities from electronically marked cables
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- guarantee USB cable compliance or conformity, as this is [very complex](https://www.usb.org/documents?search=&category%5B%5D=49&type%5B%5D=56&tid_2%5B%5D=41&items_per_page=50)
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alternatives
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------------
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- [USB micro-B cable tester](https://www.cuvoodoo.info/cuvoodoo-gadget-micro-usb-cable-tester-v2/): only does micro-B cables
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- [USB A-C cable tester](https://www.cuvoodoo.info/cuvoodoo-gadget-usb-a-to-usb-c-cable-tester-v1/): only does USB type A to type C cables
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- [USB C-C cable tester](https://www.cuvoodoo.info/cuvoodoo-gadget-usb-c-cable-tester-v2/): only does USB type C to type C cables
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- [DT3 Data Cable Detection Board](https://www.aliexpress.com/item/1005006302832038.html): does not check shield, battery charging, USB 3.0
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- [USB Cable Checker 2](https://www.tindie.com/products/bittradeone/usb-cable-checker-2-assembled/): too complex and expensive
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- [USB Cable Tester](https://github.com/alvarop/usb_c_cable_tester): only for USB-C and you have to understand and interpret the signals
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