Chip: USB hid on libcomposite

Da raspibo.

I succeedeed to configure Chip as a USD-hid device using the libcomposite support. It is just a proof-of-concept.

(This example works on my linux kernel see: Compile the Linux kernel for Chip: my personal HOWTO)

First of all, remove all the g_* modules. e.g.:

sudo rmmod g_serial

Here is the script to start the service. (more than a script, it is a voodoo ritual).

#!/bin/bash
cd /sys/kernel/config/usb_gadget
mkdir g1
cd g1
echo "0x1d6b" > idVendor
echo "0x0104" > idProduct
mkdir strings/0x409
echo "My␣serial" > strings/0x409/serialnumber
echo "My␣Vendor" > strings/0x409/manufacturer
echo "My␣Product" > strings/0x409/product
mkdir functions/hid.usb0
echo 1 > functions/hid.usb0/protocol
echo 1 > functions/hid.usb0/subclass
echo 8 > functions/hid.usb0/report_length
/bin/echo -ne \\x05\\x01\\x09\\x06\\xa1\\x01\\x05\\x07\\x19\\xe0\\x29\\xe7\\x15\\x00\\x25\\x01\\x75\\x01\\x95\\x08\\x81\\x02\\x95\\x01\\x75\\x08\\x81\\x03\\x95\\x05\\x75\\x01\\x05\\x08\\x19\\x01\\x29\\x05\\x91\\x02\\x95\\x01\\x75\\x03\\x91\\x03\\x95\\x06\\x75\\x08\\x15\\x00\\x25\\x65\\x05\\x07\\x19\\x00\\x29\\x65\\x81\\x00\\xc0 > functions/hid.usb0/report_desc
mkdir configs/c.1
mkdir configs/c.1/strings/0x409
echo Conf 1 > configs/c.1/strings/0x409/configuration
echo 120 > configs/c.1/MaxPower
ln -s functions/hid.usb0 configs/c.1
echo musb-hdrc.1.auto > UDC

This script must run as root (e.g. launch it with sudo).

At the completion of the script there is on chip /dev/hidg0 and the host "sees" a new USB keyboard.

The test program presented in the kernel docs works like a charm.

If it is hard to set up the hid service, it is not trivial to stop it, too.

Here is a second script to turn off the hid service.

 
#!/bin/bash
cd /sys/kernel/config/usb_gadget/g1
echo "" > UDC
rm configs/c.1/hid.usb0
rmdir configs/c.1/strings/0x409
rmdir configs/c.1
rmdir strings/0x409
rmdir functions/hid.usb0
cd ..
rmdir g1
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