XDIMAX Products Forum

Hi,
I want to use the SUB-20 module as SPI slave. The master is a DSP board sending data via the SPI-20 module and USB to the PC at a medium data rate of minimum 1Mbit/s. On the PC I use the C API.
Actually I have a test running at low data rate (circa 10 kbit/s). If I increase the data rate I get many errors (lost data) in the received data.

My configuration:
SPI_SlAVE, SPI_CLK_2MHz, SPI_CPOL_RISE, SPI_SETUP_SMPL.
On the PC I have an application written with Visual C saving the received data to a log-file with the API function “rc = sub_fifo_read( hndl, in_buff, 128, 2000 )”.
I send little blocks of data (2-6 bytes) from the SPI master (DSP) to the SUB-20 module and then I wait without sending data. Variaring the pause I vary the medium data rate.
It seems that the bottle neck is the USB-transfer or the small buffer in the module. But if in one USB-frame (1ms) a block of 128Bytes (or 2 blocks of 64 bytes) will be transferred a data rate of 1024kbit/s should be possible. Someone has reached this or a higher performance?
Why is my data rate performance low?

Thanks your help.

HI,
First of all you can try to increase read size.

In next release we will have special flag FIFO_READ_FULL that will guaranty 64 bytes divisible reads. It will increase performance.