The firmware in the device specifies the maxPacketSize in the
endpoint descriptor. If you can rebuild the firmware for your
scanner, you can change it. However, be aware that for USB full
speed devices the MaxPacketSize is limited to a maximum of 64 bytes.
For Hi-speed devices, the MaxPacketSize must be 512 bytes.
You can send requests of any size, and the USB stack will break your
request into multiple maxPacketSize requests. If reading from a
Bulk IN pipe, you should always request a multiple of maxPacketSize
so that you do not risk loosing data from your device.
Regards,
David Ferguson
USB Software Team
Apple Computer
At 11:28 PM -0800 1/8/05, nishino tetsuya wrote:
I am programming a USB communication module for the scanner device
using IOUSBInterfaceInterface, etc. and I would like to change the
maxPacketSize for a bulk pipe. Right now I am using a default value
64 byte. Can someone tell me how to change it?
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