I have a very simple embedded application I am building, for which having an OS would be overkill (not worth adding and dont have space for flash memory for filesystem). I will just be using the interrupts inherent to the AT91SAM9261 to run the system.

The problem is that I need to attach a USB device to this board. This device is a custom class type of device, where the host's application code will simply want to call 'read/write' functions that send/receive certain amounts of data.

My question is this: The AT91SAM9261 has a USB Host Controller that is OHCI compliant. What is the best way to write a driver to do this without using, e.g. Linux (or any OS). Is it possible to just take standard OHCI driver source code and just compile it for this processor? If so, is there free OHCI driver code available anywhere?

I'm a USB and embedded micro newbie, so any help would be appreciated. Thanks.

I would also like to find a "free" OHCI driver.

I have found several commercial products (SMC, Jungo, thesyscom)
Most seemed to be derived from BSD.

If you find a promising package please post

Good Luck,

Larry

I have actually decided to just write my own driver. Since I am only interfacing to a single device, which will be plugged in at all times, I have decided that it won't be too difficult to just write a simple driver.

It sounds good !

I also intend to use the USB host port from a simple OS less application on the AT91SAM9263. I am having trouble finding relevant information of how to access the USB host port however. Of the >800 pages in the Atmels AT91SAM9263 Preliminary document only three pages are dedicated to the USB host ports, and those pages does not say much either... Not a single USB host/ OHCI memory/register location is mentioned.

The .h files in the software framework (AT91lib & USB framework) has no USB host related definitions what so ever. From what I can tell the USB host functionality on the Atmel AT91SAM9263 is totally unsupported/undocumented.

Have I missed something? Is there any other place where I can find relevant information?

The host controller follows the OHCI spec, so all of the registers correspond directly to what is in that spec. I haven't gotten around to writing code yet, but from reading the spec and matching it up with what's in the datasheet, it looks like the USB Host Port (UHP) registers start at address 0x500000, where the registers are defined as in Section 7 of the OHCI spec, 'Operational Registers'. You can download the OHCI spec from here:

ftp://ftp.compaq.com/pub/supportinformation/papers/hcir1_0a.pdf

I finally got around to starting this code, and I am having trouble figuring out the appropriate UHP startup sequence. What I am doing so far is:

1. Enable the UHP peripheral by enabling the clocks.
2. Check revision of UHP in HcRevision register.
3. Reset Host Controller (HC)
4. Initialize the HCCA, Control, and Bulk Endpoint Descriptors.
5. Enable the interrupts I want on the UHP.

Is this correct? The ohci spec says that the HC reads the address of the HCCA (that the Host Controller Driver inits, step 4 above) upon initialization. When does that initialization of the HC occur? Do I have to change the status of the HC from UsbSuspend to UsbOperational in the HcCommandStatus register?

The other question I have is I do not understand what the Function Address and Endpoint Number fields are supposed to be in the Endpoint Descriptor structure.

Thanks.

If you have not figured out an answer to your question, the following may help.

Sun Microsystems developed a platform called SunSpot based on the AT91RM9200 processor. For it they have developed a library for controlling USB. If you are interested, you can download their source code from svn:

https://spots-core-libraries.dev.java.n ... ries/trunk

username: guest
password: guest

Look into the trunk/arm-bootloader/src/usb directory to see the USB code.

Although the processor they use is a little different, hopefully this example will be helpful.

Thanks exvagabond,

I will take a look at this, but unfortunately this is for a device side driver and not host side.

I have actually made a fair amount of progress on this recently. I can do control transfers. Bulk transfers however hang because for some reason the bus enters the SUSPEND state. I'm trying to figure out whether it is the device or my host that is causing this.

Thanks again.

Would you be willing to share here some of your initialisation code?

I too am struggling to find any documentation on the USB Host Controller functions. All the examples are for the USB device ports!

I have tried to port a USB host drive from the uboot1.1.5 to drive a storage in my board, it seemed like working well, but is not so stable for that which capacity is more than 2GB.
In the uboot code, you can fine the host side code to drive an USB.

Hello budhe888,
I'm working with at91sam9g45.Can you please help me in the same regard.