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Return to USB host.

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USB host

The mini-USB port on both the Neo 1973 and the Neo FreeRunner supports both USB host and USB device. This opens up a range of possibilities, such as adding USB cameras and USB input devices.

Selecting USB host mode

By default, the mini-USB port is in device mode. To tell the Neo that it is logically a host:

echo "host" > /sys/devices/platform/s3c2410-ohci/usb_mode

Independent of the logical mode of the USB port, the Neo FreeRunner can provide 5 volt USB power to an attached USB device. To enable this (not available on Neo 1973):

echo "1" > /sys/devices/platform/neo1973-pm-host.0/hostmode

Note: You may want to run ifconfig usb0 down prior to switching to USB host mode, as the Neo's USB networking may not like having its USB port disappear. You'll probably want to ssh into your Neo over WiFi or Bluetooth before starting all of this, alternatively use an on screen keyboard.

Providing power to connected USB devices while in host mode

Normally, USB host ports provide power to any connected USB device.

Available power in host mode is the full maximum of 500mA according to USB-specifications on the Neo FreeRunner, and no power is available in host mode on the Neo 1973. If your USB device respects USB-standards and consumes not more than 500mA, you may connect it directly to your Neo FreeRunner.

To provide power to USB devices attached to your Neo 1973, or to provide power to your Neo FreeRunner while USB-device connected, you can provide power by using a (modified [for powering FreeRunner]) powered USB hub (see below), or by manually injecting power into the attached USB device (and Neo FreeRunner) via one of the specialized_USB_cables.

Powered USB hubs known to work with the Neo

(please add any known to work)

Providing power to run and charge the Neo while in host mode

A slightly separate issue is power to run and charge the Neo (both types) itself. When the USB port is in device mode, the Neo FreeRunner/1973 can be powered and recharged via the USB port, but when in standard host mode, the Neo FreeRunner is set to provide power and does not charge. Fortunately, control of the direction of power (in or out) is independent of the personality of the USB port (host or device):

To recap, the direction of power can be controlled:

Set to 0 (default), no power is provided at the USB port, charging is enabled, and host 15K pulldowns are removed from D+ and D-:

echo "0" > /sys/devices/platform/neo1973-pm-host.0/hostmode

Set to 1, provides up to 500mA USB power at the USB port (FreeRunner only), disables charging from USB, and applies 15K pulldowns to USB D+ and D-:

echo "1" > /sys/devices/platform/neo1973-pm-host.0/hostmode

Next, power must somehow be injected. An unmodified powered USB hub only provides power to the connected devices, but not to the connected host, so the only solution here is to modify a USB-hub¹) or to create a custom cable which will inject power into the host. See specialized_USB_cables for some examples.

Finally, there is the question of charge rate. The charging logic in the Neo will only charge at 100mA by default. Charging at 500mA will take place only if the charging device responds appropriatly to USB negotiation to increase power consumption. Charging at 1000mA will only take place if the Neo detects the appropriate resistor on the ID pins.

You can manually set the charge rate. See Forcing_fast_charge_mode

¹) often it's sufficient to short a diode in USB-hub to feed power to the host-connector too.

Power Concerns

You'll need to force the Neo to go into fast charge mode, since it can't do its usual power negotiation over USB.

echo -n "fast_cccv" >  /sys/devices/platform/s3c2410-i2c/i2c-adapter/i2c-0/0-0008/chgmode

(Also this should be done by kernel when seeing 47K at ID-pin)