Hello;

I have a design based on an AT91SAM7S256 ARM micro that is both powered and connects with the PC through USB. It acquires info from some MEMS and sends it to the PC.

I am having some problems regarding the size of the packet sent from my micro to the PC host. The maximun data packet size is 32 bytes and I cannot configure it to 64 bytes, which is the lenght that I need.

I am reading the AT91SAM7256 datasheet, but I do not understand which registers I have to modify.

Anybody knows what can I do. Thank you very much!!!!!

Hi

The SAM7 have fixed maximum endpoint FIFO lengths:
- endpoints 0 and 3 have have size 8 bytes.
- endpoints 1 and 2 have size 64 bytes.

The endpoints lengths are not configurable in the device (the maximums are the maximum FIFO sizes implemented). The endpoint length used is controlled in the driver software (and potentially limited by the HW if set too high). This suggests that the driver SW is not working with the 64 bytes but instead is working with 32 bytes - check also the details in the configuration descriptor used during enumeration since the end point size is also defined here and the host would therefore also restrict the packet size sent based on this.

Regards

Mark

www.uTasker.com