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these are the hardware design files for **insert project name here**. |
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the CuVoodoo USB hub is a 7-port USB 2.0 hub meant for device testing. |
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purpose |
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======= |
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most USB hub are super cheap and crappy, leading the poor connection connection and data transfer. |
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there are industrial USB hubs, but they are bulky and very expensive. |
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to solve this issue I decided to design my own USB hub, tailored to my needs. |
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when developing and testing hardware, you often end with a lot of USB devices connected. |
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USB allows to have up to 128 devices, but only with a maximum depth of 7. |
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thus you are only allowed to have a maximum of 5 USB hubs between computer and devices, and I often have to plan my setup to not reach this limit. |
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most 7-port USB hubs use two 4-port USB hub, the seconds being connected to the first. |
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there are some exception to that, but they are rare, old, and often not advertised as such. |
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this heavily limits the number of end devices. |
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this device is a 7-port flat USB hub, preventing reaching this limit too often. |
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the incoming and outgoing USB ports are individually ESD protected. |
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this safety becomes important when developing, testing, and handling bare electronic devices. |
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this also comes in handy against when connecting circuit with different ground potentials. |
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ESD protections already saved my day twice. |
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the issue is that they can blow without you noticing, but at least they protected the device once. |
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each output port is current limited to 500 mA. |
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no device should draw more that this specified limit. |
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it if does, there is very probably an issue with the device. |
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this protection allows to isolate the faulty device and not have it affect all other connected devices, or the hub itself. |
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the fault is also detected and reported by the hub to the host computer. |
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each output port is power controlled. |
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this allows to remotely switch on an off individual devices. |
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this is an important requirement when developing and testing devices, which require a power cycle. |
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additionally, a switch next to the power can force the power off state. |
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the USB hub can be self-powered (through the USB input port), externally powered by 5V, or externally powered by anything between 6 and 40V. |
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this allows to use higher voltage power supplies to provide enough current to all power. |
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the 5V are not feed back to the host. |
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each output port comes with a high voltage output power port, connected to the high voltage input port. |
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this allows to power devices which require more than 5V (e.g. 12V externally powered devices). |
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each of these power output is controllable. |
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as with the 5V USB power output, this allows to remotely switch on an off individual devices. |
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each port has status LEDs, indicating the speed and power of the connected device. |
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the board uses proper impedance and differential signal routing to provide clean USB transfer. |
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design choice |
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============= |
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USB 3.0 |
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------- |
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this hub is only for USB 2.0 devices. |
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by far this are most of the devices I develop. |
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is makes it simpler and keeps the cost reasonable. |
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I often even disable USB 3.0 because of the 13-device limitation of the Intel xHCI. |
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when I need USB 3.0 for the very few devices, I connected them to the computer directly. |
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USB2517 |
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------- |
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I wanted to use the FE2.1 7-port USB hub chip. |
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it does not need an external voltage regulator or crystal. |
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and it is easier to solder thanks to its TQFP package, and provides all required functionalities. |
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sadly I could not find a source for the 64-pin packages, and the 48-pin variant does not provide all required functionalities. |
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thus I had to fall back to the Microchip USB2517, which uses a harder to solder QFN package. |
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current limitation |
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------------------ |
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the few USB hubs that have current limitation on the output, use a MIC2026. |
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this does limit the current to 500 mA, but only in constant current mode. |
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the fault is reported (e.g. to the hub, back to the computer), but it is up to the user to power off the faulty device. |
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instead I use poly-fuses, which automatically cut the power once the limit of 500 mA is reached. |
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this is faster, and removes user-based actions. |
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the fault is still reported. |
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this is very useful when testing devices. |
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LED color |
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--------- |
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the USB specification, LEDs are used as port indicator (section 11.5.3) |
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- off: powered off/disconnected |
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- amber: current limitation reached |
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- green: enabled or transmitting |
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instead the following color scheme is used: |
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- green off: power off or over-current |
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- green on: power on |
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- red: low speed device connected |
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- blue: full speed device connected |
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- purple (red+blue): high speed device connected |
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- red and blue off: disconnected |
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usage |
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===== |
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