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@@ -7,7 +7,7 @@ and two USB cables, connected like this:
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[host/target] <-------> [USB debug key] <-------> [client/console]
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-1. There are three specific hardware requirements:
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+1. There are a number of specific hardware requirements:
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a.) Host/target system needs to have USB debug port capability.
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@@ -42,7 +42,35 @@ and two USB cables, connected like this:
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This is a small blue plastic connector with two USB connections,
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it draws power from its USB connections.
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- c.) Thirdly, you need a second client/console system with a regular USB port.
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+ c.) You need a second client/console system with a high speed USB 2.0
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+ port.
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+
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+ d.) The Netchip device must be plugged directly into the physical
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+ debug port on the "host/target" system. You cannot use a USB hub in
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+ between the physical debug port and the "host/target" system.
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+
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+ The EHCI debug controller is bound to a specific physical USB
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+ port and the Netchip device will only work as an early printk
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+ device in this port. The EHCI host controllers are electrically
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+ wired such that the EHCI debug controller is hooked up to the
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+ first physical and there is no way to change this via software.
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+ You can find the physical port through experimentation by trying
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+ each physical port on the system and rebooting. Or you can try
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+ and use lsusb or look at the kernel info messages emitted by the
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+ usb stack when you plug a usb device into various ports on the
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+ "host/target" system.
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+
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+ Some hardware vendors do not expose the usb debug port with a
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+ physical connector and if you find such a device send a complaint
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+ to the hardware vendor, because there is no reason not to wire
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+ this port into one of the physically accessible ports.
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+
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+ e.) It is also important to note, that many versions of the Netchip
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+ device require the "client/console" system to be plugged into the
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+ right and side of the device (with the product logo facing up and
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+ readable left to right). The reason being is that the 5 volt
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+ power supply is taken from only one side of the device and it
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+ must be the side that does not get rebooted.
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2. Software requirements:
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@@ -56,6 +84,13 @@ and two USB cables, connected like this:
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(If you are using Grub, append it to the 'kernel' line in
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/etc/grub.conf)
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+ On systems with more than one EHCI debug controller you must
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+ specify the correct EHCI debug controller number. The ordering
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+ comes from the PCI bus enumeration of the EHCI controllers. The
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+ default with no number argument is "0" the first EHCI debug
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+ controller. To use the second EHCI debug controller, you would
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+ use the command line: "earlyprintk=dbgp1"
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+
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NOTE: normally earlyprintk console gets turned off once the
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regular console is alive - use "earlyprintk=dbgp,keep" to keep
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this channel open beyond early bootup. This can be useful for
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