Usb vs. Ftdi

Yendor

Hi guys,

Just a question on what's typically happening in the industry·with usb, etc.

As an example I was on an interview a bit ago,·and the interviewer asked me about·my USB knowledge.

I told him that details of using the FTDI chip communicating·with it serially, and was quite satisfied with my response.· But he surprised me by·emphasizing that that's not USB knowledge or using the USB protocal.

I took it as using the FTDI chip or similar is not an acceptible practice in the industry.

This was for·a relatively small company specializing in audio, and I'm wondering if they're wasting a lot of time developing their own firmware drivers and pc drivers, or if I'm totally off base.· It may have been·a trick question, too, but felt I held my own.·

Of course there's the reliance on using FTDI's·device drivers, could this be the case?

What are your thoughts?

·

Leon

He presumably wanted you to tell him about this sort of stuff:

en.wikipedia.org/wiki/Universal_Serial_Bus

not about how you would connect an FTDI chip to a MCU.

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Leon Heller
Amateur radio callsign: G1HSM

bill190

There is a USB "Type A" device and a USB "Type B" device. Called "Host" or "Device".

There is specific wiring as to the connectors. There is a question as to power provided on the USB wire. You would not want a USB "host" (like a PC) *and* a USB "device" (like a keyboard) to both be placing power on the USB line.

Micochip has·what is called "USB Framework for PIC18, PIC24 & PIC32" which you can download for free and in this I think are C source files for USB Host and USB various devices like Mouse, Mass Storage, and Generic driver. I think you need to register to download this from Microchip, but the following is the download page for that...

http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=2680&dDocName=en537044

A larger download is the Microchip "Applications Library". This would have more device and host examples...
http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=2680&dDocName=en547784

The files with the programming would be called .c or .h·(C programming language). These would be the files to look at as to example programming. Or there may be·.asm files which would be assembly program files.

Ignore other files which end in .mcp, .mcw, .hex, .cof, .map, .o, etc. These are "put it all together" files.

I looked in the Propeller Object Exchange Protocol area and did not see any USB stuff.

Perhaps as a learning project, you can get a USB connector, then try to connect a Propeller as a USB device? (Make your own FTDI like interface.) Be careful to not connect to +power if you are going to plug the other end into a PC.

Chips which have a USB connection have D+ and D- (or more) connections. So I think you would need another chip to add to the Propeller to do this?

Here is more info on this...
http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1486

Here is a search for USB IC and there are all sorts of different USB IC's to check out...
http://www.altavista.com/web/results?itag=ody&q=usb+IC&kgs=1&kls=0



Post Edited (bill190) : 5/24/2010 1:13:55 PM GMT

BradC

Yendor said...
But he surprised me by emphasizing that that's not USB knowledge or using the USB protocal.


What are your thoughts?

It's important to know what you don't know. He's right of course, talking about using a serial interface to an FTDI chip is the equivalent of describing that moving the mouse makes the pointer on the screen move. The both use USB (mostly), but that's about as indepth as it gets.

Grab a copy of the USB2.0 specification document from www.usb.org and have a read. It's quite detailed.

The Propeller has been able to behave as a USB device since '07, and recently as a USB master also.

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