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

[Frank Pagliughi <fpagliughi@mindspring.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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