Achieving practically possible maximum speed for USB2.0

Hello All,

I have been successful in implementing the USB2.0 communication
protocol for ISP1582 USB Peripheral Controller. With my current code I
am able to achieve the data rate of only 24Mbits/sec, which is too less
comparable to the actual data rate that can be practically achieved. I
request for your support and valuable suggestions in achieving the
maximum possible data rate. Before listing my doubts let me jot down
the ISP1582 configuration I am working with and all that I have tried
on my side to achieve a better rate.
ISP1582 USB Peripheral Controller Configuration is as follows:
Number of Enabled Pipes :- 02, ENDPOINT1IN and ENDPOINT1OUT
Type of Data Transfer Selected :- BULK
Type of Interrupt :- Active Low / Edge
Triggered(Level Triggering also tried, but no effect)
Buffer Type :- Double Buffering(Single
Buffering also tried, but no effect)
Setting of Various Registers :- MODE REGISTER
-> 0x0D
INTERRUPT
CONFIGURATION REGISTER -> 0x68
INTERRUPT ENABLE
REGISTER -> 0x0000D3B9
DMA CONFIGURATION
REGISTER -> 0x00
DMA HARDWARE
CONFIGURATION REG -> 0x00
Currently I am not using DMA.
Setting of Enabled EndPoints :- ENDPOINT1IN -> Maximum
Packet Size is 512Bytes, Transfer type is Bulk and Double Buffering
disabled
ENDPOINT1OUT ->
Same as ENDPOINT1IN
I have also tried with single buffering.
With all these settings I am achieving the data rate of 24Mbits/sec.
Now, in order to increse this value I did the following exercises:-
1) Earlier the processor which I have interfaced to ISP1582 USB
Peripheral Controller had 3 wait states. That is the read/write cycle
for the external read or write is extended by 10nsec for one wait state
inserted. I reduced the wait states from 3 to a single wait state which
is the minum possible that I can afford for getting the chip
enumerated. Reducing further fails the enumeration process.
2) Next, I have written the complete code in C language. I converted
the two main functions that are being called many a times(i.e. the read
and write from the ISP1582 USB Peripheral Controller Buffer) from C to
Assembly. This also didn't help.
3) While sending the data from internal memory of processor to the
host PC via USB, I am reading the data from internal memory and
duplicating it in some Tx buffer in the internal memory of processor.
Then in order to actually send the data I am using the Tx Buffer for
writing the data to the USB buffer. I commented the duplication code
and jus wrote some junk data directly from the Tx buffer. This also
made no difference in speed.
The configuration of my host PC are:
2.4GHz, 256MBytes RAM and Windows XP.
On opening the Device Manager of my computer I clicked on UNIVERSAL
SERIAL BUS CONTROLLERS. There 4 USB Host Controllers were listed to
which the USB Root Hubs are attached. On checking the properties(by
doing a right click on each listed USB Host Controller and selecting
properties) of each USB Host Controller, I found in Advanced tab option
that the Bandwidth for each USB Host controller is only 10% which is
reserved for that particular host controller. So, I doubt that does
this thing will limit the speed that I can acheive. That is if a
particular host controller has been assigned only 10% of the system
bandwidth then will it affect the maximum USB speed that I can achieve.
If yes, then how can I achieve the practically possible speed with my
ISP1582.
My other doubts are as follows :-
1) When I reduced the wait states then why there was no effect on
the speed.
2) Also, when I wrote the functions from C to assembly then it is
expected that there should be some increase in the speed, then also
there was no effect, why?

Please Help !
I would be obliged for your valuable suggestions.

With Best Regards
Himanshu Jain
--------------------------------------------------------------------------------

.

Relevant Pages