Hi there,
I'm in the process of designing a VME=>USB interface, and I wanted to use the
FT232H, but according to FTDI, the throughput on Linux is only ~9MBytes/sec
using current kernels. In the past, it was ~40MBytes/sec. Sadly my Arm board is
delivered running Linux 3.4.29
I don't really want to go back to the "olden days" of kernel 2.6.27-57 - I'm
not even sure it's possible on my embedded ARM board, so I was wondering if
anyone knew the reasons for such a drastic bandwidth reduction. If it's
something I can live with in my embedded situation, I'd prefer to revert the
change and lose whatever functionality was gained by slashing the bandwidth by
4.
Basically I need to be able to put 20 MBytes/sec through the USB port. The
FT232H parts are very attractive because they offer a simple FIFO-style
interface and one doesn't have to implement an entire USB stack, which is much
harder when you don't have a CPU ...
Cheers
Simon.
Mail from FTDI:
---8<---8<---8<--- C u t h e r e ---8<---8<---8<---
Simon:
You could use Sync FIFO mode, but I’m afraid there is another “gotcha” to be
aware of - with newer Linux kernels (>2.6.28-3), Sync FIFO throughput is
limited to 9 MByte/sec
With the older kernels (2.6.27-57 and older) Sync FIFO will run at 40
MByte/sec. Since you are using ARM Linux, there is a good chance you have an
older kernel.
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