uClinux lpc17xx: Support for USB Host interface

[lpcware]

Content originally posted in LPCWare by Vladimir Khusainov on Wed Jan 18 02:21:08 MST 2012
In continuation of the topic created by Kevin Wells on 2011-12-22 (see "Thoughts on the LPC1788 uCLinux port on the Embedded Artists board"), here is how uClinux can be used to provide support for USB devices with LPC1788.

The LPC1788 MCU shares the OHCI USB Host controller IP with the LPC2478 device. There is a Linux distribution available for LPC2478 device that already has a device driver for the specific USB Host controller interface.

Port of the device driver to the LPC1788 required setting up some clocks and assigning some MCU pin functions appropriatelly but other than that the device driver just worked on the LPC1788.

Of course the Linux (uClinux) kernel provides ample driver support for various USB device so this all is available out-of-box. The Linux kernel needs to be configured with appropriate build-time options in support of required USB devices but this is a standard thing for Linux.

Here is a sample session that shows how to use a USB Flash stick with LPC1788. I ran this session on the Embedded Artists LPC1788 board with a USB Flash device preformatted on a Windows PC inserted into the USB host port of the board.

After reset, U-boot comes up on the board:

<code>
U-Boot 2010.03-linux-cortexm-1.3.1 (Jan 17 2012 - 14:16:30)

CPU  : LPC178x/7x series (Cortex-M3)
Freqs: SYSTICK=108MHz,EMCCLK=54MHz,PCLK=54MHz
Board: EA-LPC1788 rev 1
DRAM:  32 MB
Flash:  4 MB
In:    serial
Out:   serial
Err:   serial
Net:   LPC178X_MAC
Hit any key to stop autoboot:  0
EA-LPC1788>
</code>

I load a bootable Linux image from TFTP and run it:

<code>
EA-LPC1788> ru netboot
Auto-negotiation...completed.
LPC178X_MAC: link UP (100/Full)
Using LPC178X_MAC device
TFTP from server 172.17.0.1; our IP address is 172.17.3.109
Filename 'vlad/v'.
Load address: 0xa0000000
Loading: #################################################################
         ####################################################
done
Bytes transferred = 1704032 (1a0060 hex)
## Booting kernel from Legacy Image at a0000000 ...
   Image Name:   Linux-2.6.33-arm1
   Image Type:   ARM Linux Kernel Image (uncompressed)
   Data Size:    1703968 Bytes =  1.6 MB
   Load Address: a0008000
   Entry Point:  a0008001
   Verifying Checksum ... OK
   Loading Kernel Image ... OK
OK

Starting kernel ...
</code>

Linux comes on the board showing the following messages relevant to USB:

<code>
Linux version 2.6.33-arm1 (vlad@ocean.emcraft.com) (gcc version 4.4.1 (Sourcery G++ Lite 2010q1-188) ) #121 Wed Jan 18 12:19:04 MSK 2012
...
usbcore: registered new interface driver usbfs
usbcore: registered new interface driver hub
usbcore: registered new device driver usb
...
ohci_hcd: USB 1.1 'Open' Host Controller (OHCI) Driver
lpc178x-ohci lpc178x-ohci: LPC178x OHCI
lpc178x-ohci lpc178x-ohci: new USB bus registered, assigned bus number 1
lpc178x-ohci lpc178x-ohci: irq 24, io mem 0x2008c000
usb usb1: New USB device found, idVendor=1d6b, idProduct=0001
usb usb1: New USB device strings: Mfr=3, Product=2, SerialNumber=1
usb usb1: Product: LPC178x OHCI
usb usb1: Manufacturer: Linux 2.6.33-arm1 ohci_hcd
usb usb1: SerialNumber: lpc178x-ohci
hub 1-0:1.0: USB hub found
hub 1-0:1.0: 2 ports detected
Initializing USB Mass Storage driver...
usbcore: registered new interface driver usb-storage
USB Mass Storage support registered.
usbcore: registered new interface driver hiddev
usbcore: registered new interface driver usbhid
usbhid: USB HID core driver
...
usb 1-2: new full speed USB device using lpc178x-ohci and address 2
usb 1-2: New USB device found, idVendor=0dd8, idProduct=173c
usb 1-2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
usb 1-2: Product: Flash Drive
usb 1-2: Manufacturer: USB
usb 1-2: SerialNumber: ff0aEC981700FFFF05D1
scsi0 : usb-storage 1-2:1.0
...
init started: BusyBox v1.17.0 (2012-01-18 12:15:11 MSK)
~ # scsi 0:0:0:0: Direct-Access     USB      Flash Drive      PMAP PQ: 0 ANSI: 0 CCS
sd 0:0:0:0: [sda] 3919872 512-byte logical blocks: (2.00 GB/1.86 GiB)
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] Assuming drive cache: write through
sda:
sda1
sd 0:0:0:0: [sda] Assuming drive cache: write through
sd 0:0:0:0: [sda] Attached SCSI removable disk
</code>

At this point, I create a device node for the USB Flash stick and mount it on a local directory:

<code>
~ # mknod /dev/usb b 8 1
~ # mount /dev/usb /mnt
~ #
</code>

I have some files and directories already on the disk:

<code>
/mnt # ls -lt
drwxr-xr-x    2 root     root         32768 Jul 12  2011 Images
drwxr-xr-x    2 root     root         32768 Jul 12  2011 Audio
/mnt # ls -lt Audio/
-rwxr-xr-x    1 root     root      25099820 Nov  5  2010 Art of gardenss.wav
/mnt #
</code>

As a stress test of sorts, let's copy the busybox multi-tool binary to the USB disk and then run it from there:

<code>
/mnt # cp /bin/busybox .
/mnt # ls -lt
drwxr-xr-x    2 root     root         32768 Jul 12  2011 Images
drwxr-xr-x    2 root     root         32768 Jul 12  2011 Audio
-rwxr-xr-x    1 root     root        235664 Jan  1 00:09 busybox
/mnt # ./busybox echo "Hello from USB disk"
Hello from USB disk
/mnt #
</code>