USB-OTG (CM-i.MX27)

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The CM-i.MX27 core module features a high-speed USB-OTG PHY (SMSC USB3317). It is connected to the mini-USB jack marked with USB-OTG on the DEV-i.MX27/35.

Linux kernel configuration

This configuration sets up full OTG mode, support for the Ethernet gadget (USB device mode) and mass storage support (USB host mode). 

Device Drivers  --->
  SCSI device support  --->
    <*> SCSI device support
    [*] legacy /proc/scsi/ support
    <*> SCSI disk support
    [*] Probe all LUNs on each SCSI device
  USB support  --->
    <*> Support for Host-side USB
    [*]   USB device filesystem
    <M>   EHCI HCD (USB 2.0) support
    [*]     Support for Freescale controller
    [*]       Support for OTG host port on Freescale controller
    Select OTG transceiver (Philips ISP1504)  --->
    [*]     Root Hub Transaction Translators (EXPERIMENTAL)
    <*> USB Mass Storage support
    USB Gadget Support  --->
      <M> Support for USB Gadgets
      USB Peripheral Controller (Freescale USB Device Controller)  --->
      [*] OTG Support
      [*] Support for OTG peripheral port on Freescale controller
      Select OTG transceiver (Philips ISP1504)  --->
      <M>   Ethernet Gadget (with CDC Ethernet support)

Test in Linux

After startup of the kernel, we will load the required kernel modules, test the USB HOST mode with a USB flash disk, and test the USB DEVICE mode with the Ethernet gadget. You will need a PC featuring the Ethernet gadget driver (a Linux PC typically includes this driver).

  • Boot Linux on the CM-i.MX27
  • Load the kernel modules
root@btmxc27:~# modprobe isp1504_arc
driver fsl_arc, Revision: 1.0
root@btmxc27:~# modprobe ehci-hcd
fsl-ehci fsl-ehci.0: Freescale On-Chip EHCI Host Controller
fsl-ehci fsl-ehci.0: new USB bus registered, assigned bus number 1
fsl-ehci fsl-ehci.0: irq 56, io mem 0x10024000
fsl-ehci fsl-ehci.0: USB 2.0 started, EHCI 1.00, driver 10 Dec 2004
usb usb1: Product: Freescale On-Chip EHCI Host Controller
usb usb1: Manufacturer: Linux 2.6.22-btmxc27-v1.0 ehci_hcd
usb usb1: SerialNumber: fsl-ehci.0
usb usb1: configuration #1 chosen from 1 choice
hub 1-0:1.0: USB hub found
hub 1-0:1.0: 1 port detected
root@btmxc27:~# modprobe arcotg_udc
ARC USBOTG Device Controller driver version 1 August 2005 init 
ARC USBOTG h/w ID=0x5  revision=0x42
root@btmxc27:~# modprobe g_ether
ether gadget: using random self ethernet address
ether gadget: using random host ethernet address
usb0: Ethernet Gadget, version: May Day 2005
usb0: using arc_udc, OUT ep1out IN ep1in STATUS ep2in
usb0: MAC 72:ec:9b:ab:9b:5d
usb0: HOST MAC ea:21:c9:08:58:39
arcotg_udc: gadget arc_udc bound to driver ether
root@btmxc27:~#
  • Now connect a USB flash disk to the USB-OTG plug. You need a cable mini-USB-A plug to USB-A-jack. We will mount and unmount it:
usb 1-1: new high speed USB device using fsl-ehci and address 2
usb 1-1: Product: USB Mass Storage Device
usb 1-1: Manufacturer: P Technology
usb 1-1: SerialNumber: 200707a41934fc
usb 1-1: device v1307 p0163 is not supported
usb 1-1: configuration #1 chosen from 1 choice
scsi0 : SCSI emulation for USB Mass Storage devices
scsi 0:0:0:0: Direct-Access     UT163    USB Flash Disk   0.00 PQ: 0 ANSI: 2
sd 0:0:0:0: [sda] 1974271 512-byte hardware sectors (1011 MB)
sd 0:0:0:0: [sda] Write Protect is off
sd 0:0:0:0: [sda] Assuming drive cache: write through
sd 0:0:0:0: [sda] 1974271 512-byte hardware sectors (1011 MB)
sd 0:0:0:0: [sda] Write Protect is off
sd 0:0:0:0: [sda] Assuming drive cache: write through
 sda: sda1
sd 0:0:0:0: [sda] Attached SCSI removable disk
FAT: invalid media value (0x01)
VFS: Can't find a valid FAT filesystem on dev sda.
mount /dev/sda1 /mnt/card
root@btmxc27:~# ls /mnt/card
testfile
root@btmxc27:~# umount /mnt/card/
root@btmxc27:~#
  • Unplug the cable from the OTG port.
usb 1-1: USB disconnect, address 2
  • Now we will connect the i.MX board to your local PC. You need a cable mini-USB-B plug to USB-A plug.
usb0: high speed config #1: 8 mA, Ethernet Gadget, using CDC Ethernet
  • Establish an Ethernet-over-USB connection to your PC. On the target, we assign the IP address 192.168.1.2:
root@btmxc27:~# ifconfig usb0 up 192.168.1.2
root@btmxc27:~# ifconfig usb0
usb0      Link encap:Ethernet  HWaddr 72:EC:9B:AB:9B:5D  
          inet addr:192.168.1.2  Bcast:192.168.1.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:11 errors:0 dropped:0 overruns:0 frame:0
          TX packets:15 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:2024 (1.9 KiB)  TX bytes:3390 (3.3 KiB)
  • Your Linux PC should have detected the connection of the Ethernet gadget. The output of dmesg should contain:
[24772.520051] usb 1-6: new high speed USB device using ehci_hcd and address 7
[24772.663767] usb 1-6: configuration #1 chosen from 1 choice
[24772.676846] usb0: register 'cdc_ether' at usb-0000:00:1a.7-6, CDC Ethernet Device, ea:21:c9:08:58:39
  • On your Linux PC, assign the IP address 192.168.5.1 to network device usb0. We use sudo because we need root privileges for this.
harald@WS-HP4600-35:~/imx/oe/btmxc$ sudo ifconfig usb0 up 192.168.1.1
harald@WS-HP4600-35:~/imx/oe/btmxc$ ifconfig usb0
usb0      Link encap:Ethernet  HWaddr ea:21:c9:08:58:39  
          inet addr:192.168.1.1  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::e821:c9ff:fe08:5839/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:16 errors:0 dropped:0 overruns:0 frame:0
          TX packets:21 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:3513 (3.5 KB)  TX bytes:4935 (4.9 KB)
  • Now ping the target from your PC:
harald@WS-HP4600-35:~/imx/oe/btmxc$ ping -c 10 192.168.1.2
PING 192.168.1.2 (192.168.1.2) 56(84) bytes of data.
64 bytes from 192.168.1.2: icmp_seq=1 ttl=64 time=2.00 ms
64 bytes from 192.168.1.2: icmp_seq=2 ttl=64 time=0.334 ms
64 bytes from 192.168.1.2: icmp_seq=3 ttl=64 time=0.374 ms
64 bytes from 192.168.1.2: icmp_seq=4 ttl=64 time=0.339 ms
64 bytes from 192.168.1.2: icmp_seq=5 ttl=64 time=0.345 ms
64 bytes from 192.168.1.2: icmp_seq=6 ttl=64 time=0.331 ms
64 bytes from 192.168.1.2: icmp_seq=7 ttl=64 time=0.337 ms
64 bytes from 192.168.1.2: icmp_seq=8 ttl=64 time=0.337 ms
64 bytes from 192.168.1.2: icmp_seq=9 ttl=64 time=0.339 ms
64 bytes from 192.168.1.2: icmp_seq=10 ttl=64 time=0.335 ms

--- 192.168.1.2 ping statistics ---
10 packets transmitted, 10 received, 0% packet loss, time 9002ms
rtt min/avg/max/mdev = 0.331/0.507/2.005/0.499 ms
  • and vice versa:
root@btmxc27:~# ping -c 10 192.168.1.1
PING 192.168.1.1 (192.168.1.1): 56 data bytes
64 bytes from 192.168.1.1: seq=0 ttl=64 time=1.475 ms
64 bytes from 192.168.1.1: seq=1 ttl=64 time=1.319 ms
64 bytes from 192.168.1.1: seq=2 ttl=64 time=1.243 ms
64 bytes from 192.168.1.1: seq=3 ttl=64 time=1.312 ms
64 bytes from 192.168.1.1: seq=4 ttl=64 time=1.223 ms
64 bytes from 192.168.1.1: seq=5 ttl=64 time=1.242 ms
64 bytes from 192.168.1.1: seq=6 ttl=64 time=1.287 ms
64 bytes from 192.168.1.1: seq=7 ttl=64 time=1.403 ms
64 bytes from 192.168.1.1: seq=8 ttl=64 time=1.254 ms
64 bytes from 192.168.1.1: seq=9 ttl=64 time=1.287 ms

--- 192.168.1.1 ping statistics ---
10 packets transmitted, 10 packets received, 0% packet loss
round-trip min/avg/max = 1.223/1.304/1.475 ms
root@btmxc27:~#
  • Disconnect the cable. You have successfully tested USB-OTG functionality!
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