EndpointDoubleBank

[lpcware]

Content originally posted in LPCWare by Shoichi Kojima on Thu Oct 04 17:55:45 MST 2012
Hi fellow developers,

I just started CDC implementation onto 11U24 by employing nxpUSBlib 0.97.

I will not connect physical UART on the other end, purely virtual byte stream.
So, maybe I need to configure doube buffer structure in Endpoint-related hardware portion.

As I browse in related code in 0.97 package, CDC Class API seems to be designed with
that kind of architecture.
For examples, in CDCClassDevice.h, "DataINEndpointDoubleBank" is found as a
member variable of USB_ClassInfo_CDC_Device_t, as well as for Data OUT Ep and
notification Ep.
But, in sample code of VirtualSerial those parameters are set 'false'.

I think in my case, I need to set this 'true' to enjoy SOMETHING that the name of the member fields encourages me.
But, I'm lost in founding detail explanation about EndpointDoubleBank.
In what document and where can I find it ?

Regards,

[lpcware]

Content originally posted in LPCWare by Shoichi Kojima on Sat Oct 06 06:15:47 MST 2012
Hi fellows,

I wrote:
>But, in sample code of VirtualSerial those parameters are set 'false'.

I tried to change it 'true' and re-compiled.
Successfully compiled, but no behavior change is observed....

I suppose, in case of 11Uxx, 'DoubleBank' would be the intentionl setting of corresponding bits in EPBUFCFG at leaset. Aditionally, at packet data handling, proper side of buffer of each endpoint would be carefully chosen by the driver.

As far as I checked EPBUFCFG register thru debugger, that is kept zero in both cases.

Furtherly, I browse the corresponding DCD source code "Endpoint_LPCU11xx.c" and found that only 0th buffer is handled and nothing seems to be made for the other buffer.
I did not test with built-in ROM code of 11U24.
But, the same result would be gotten, I guess...

One more thing that reminds me of a kind of doubt of un-employment of the benefit from the double buffer feature that HW provides is the one of the "Known issue:" listed in nxpUSBlib 0.97 "Get it" page.
It says,
"•Rapid transfers to the VCOM example on LPC11u14 causes a loss of characters"

I guess this fact may have something to do with my guess from my slight investigation about double buffer usage in nxpUSBlib shown above.

I might mis-investigate...
Can anybody who had tried the same kind of application imlementation show the comments ?
I hope someone in nxpUSBlib team staff will do soon.


Regards,