Re: [ECOS] Help getting started: PCI/USB

[Frank Pagliughi <fpagliughi at mindspring dot com>]

Robin Randhawa wrote:

> On Friday 07 April 2006 02:48, stevemors@gmail.com wrote:
>
>  
>
> > I have been tasked with a project that involves a PCI-to-USB slave
> > device on a PC platform. This is supposed to allow the PC to act as a
> > USB slave.
> >    
>
> Chipsets that provide a USB Host controller Interface AND a slave device 
> interface are becoming increasingly common. Not surprising to see a slave 
> only interface for PCs. Would aid slave side USB development I guess.
>
>  
>
> > 1. Would the driver for this device be a USB driver wrapped in a PCI
> > driver? Would I look at existing eCos PCI and USB drivers and create
> > some sort of hybrid of these?
> >    
>
> As Andrew pointed out, there aren't any drivers for PCI per se. PCI is a 
> busing scheme that allows access to peripheral memory with a view to 
> dynamically mapping the devices in the CPU's address space and also allowing 
> access to the device's configuration space.
>
> In order to use PCI as an access mechanism, a PCI Host controller needs to be 
> setup and that is usually done first by the BIOS.
>
>  
>
> > 2. The PC bios configures the PCI bus and devices. This means CPU-PCI
> > address translation is unknown to eCos, correct? How can I fill in
> > this information when this configuration has been skipped? (Doesn't
> > redboot have to do this?)
> >    
>
> The address mappings done for each PCI-accessible device are done via device 
> specific Base Address Registers. These are filled in by the BIOS as a 
> temporary mapping to allow stuff like ethernet controllers etc to work at 
> boot-time. The BARs are re-written by the OS as deemed necessary. I would 
> think that eCos would do the same to suit the address map of the platform in 
> question.
>
> The key here is to understand that a USB Slave controller is a USB device that 
> is accessible to the CPU via a PCI bus.
>
> Cheers,
> Robin
>
>
>  
I'm doing the same thing right now. We started with a Philips D12 then 
an ISP1181 on the PC/104 (ISA) bus. Now we need some more speed, so the 
hardware guy has started on a PC/104+ (PCI) board using a PLX NET2280 
USB2 slave chip. So I'll probably be writing  the software by the end of 
the month.

If you haven't chosen hardware yet, have a look at the NET2280. It 
interfaces directly to the PCI bus, and there's already a Linux USB 
gadget driver written. Obviously, Linux and eCos drivers are 
significantly different, but at least it'll start giving you some ideas.

Frank Pagliughi


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