What is USB Enumeration?

[JazzRei]

Hi..

I'm trying to design to tap power from USB port and supply to a device.
I know through USB enumeration process, it goes through the transition of
Attached--->Powered--->Default--->Addressed--->Configured.
I'm using a PIC18F4550 which support USB interface.
Can anyone do explain in details of the process?

Appreciate for the feedback.

 

[kekon]

In a nutshell, the USB enumeration is a process of sending some commands and receiving data from the enumerated device to gather information about the device (device name, VID and PID numbers, number of endpoinds, required power, name of the company that made the device etc.)
When you plug your device into USB port the PC (named "host") sends some commands which must be implemented by each USB device (no matter what device type is). For example, the first command which is sent by the host is command called "GetDeviceDescriptor". The DeviceDescriptor is an 18-byte data structure containing the most important information about your device. If you want to know details about how USB enumeration process works (and everything about USB interface) i recommend you read a very good article about it:

**broken link removed**

 

[JazzRei]

Hi...

I did come by this article before. But I don't really understand the indepth. What are the impt things I should know for USB enumeration to work?

 

[kekon]

I don't think you will find better article describing how USB enumeration works...
The most important things you must know are described in the article.
First of all you must know what are the tokens, ACK, NACK etc., what are descriptors and their structure. Without that knowledge you will not be able to write software in your PIC18 device.
Try to read the article again and be patient.

 

[JazzRei]

Thanks for ur guidance. I will read the article again.

 

[JazzRei]

Hi kekon,

Can I check with you regarding the 4 different transfers (control, interrupt, isochronous and bulk)? I dun really understand... If possible, can u explain to me.

Thanks.

 

[ckshivaram]

http://www.delcomproducts.com/downloads/USBPRGMNL.pdf

---------- Post added at 23:30 ---------- Previous post was at 23:29 ----------

http://www.devasys.com/PD11x/JHWP.pdf

**broken link removed**

 

[PaulHolland]

Have a look: Embedded Adventures: USB part 1 - Introduction