18F2550 / 18F4550 USB

I made a USB-Serial converter using the PICDEM FS USB board (and actually using the older PICDEM USB modified for full speed), and I am able to run it at 57.6 kB, or 4800 characters per second. But I'm not sure of the actual messages per second.

There are good discussions on this in the Microchip User's Forum

In the thread:

there is a discussion of isochronous data rate, and it appears that all FS USB modes work with 1 mSec time slices, each of which can transfer a packet of 1023 bytes, for a maximum throughput of about 1,000,000 bytes per second. But apparently the 18F devices do not have enough RAM to support this.

Here is a useful table that was referenced on the forum. But read the thread for more info.

Paul

Hi Paul. Thanks for the re. and for pointing out the thread.

It looks from the posts I saw there that the best this little beast can do is limited to a packet per frame (1 micro) period, even though the protocol specifications states that control/bulk modes aren't tied to the endpoing poll (re)cycle delay.

Though I confirm I ran tests that showed about 4500 Pk/S (of 3 bytes each) using a control input (pc>pic) endpoint and a bulk out (pic>pc) endpoint. So pick your flavor;

- I am violating the protocol

- My test results are wrong

- There is light, and a way to do it... in the end

Whoever ran tests using full-speed & bulk and/or control transfer modes, your test results would be more than welcome.

Thanks.