2011-04-27 05:50:32 external USB host chip
Rob Maris (GERMANY)
For a BF51x-based project, I'm considering the use of an external dual USB interface capable of "doing" host functionality. Most of the USB host drivers available in the linux kernel tree represent devices no longer recommended for new designs (e.g. USB_EZ-extenders' ISP1362. Targeted device: ftdi's VNC2 family of chips. However, a driver must be created. The alternative: CY7C67200 (driver present) is too expensive and communication to a host controller is limited to a parallel bus.
I'm going to estimate efforts in creating a VNC2 driver. The VNC chip supports e.g. parallel bus and SPI (and this chip is firmware-controlled). I'd prefer to use the SPI subsystem, unless it is advised not to do so (e.g. when problems may be expected - driver topics, DMA, ...).
Finally, USB devices that should be recognized by the system will be WLAN, GSM, GPRS devices. Hints from experienced readers in this field are appreciated as well as from other potential stakeholders.
2011-04-27 11:46:17 Re: external USB host chip
Mike Frysinger (UNITED STATES)
there is also the SL811 part, but that might be parallel only as well.
i dont think we've tried any USB parts over SPI. my gut reaction would be that performance wouldnt be as good as a parallel part. i think we've gotten the SL811 part running at 125MHz SCLK.
usually for WLAN/GSM/GPRS parts, people get one that connects directly to the SPI bus rather than going through USB.
2011-04-27 13:11:09 Re: external USB host chip
Rob Maris (GERMANY)
The SL811 is not in focus because it also provides only one channel.
Regarding the USB host: the customer wants a solution that relies on a standard connector to connect to such modules. Other modules out there with SPI and/or parallel (compact flash style) interface tend to have their own non-standardized connector assignments - unwanted dependency on single vendor.
Regarding the interface: whether SPI or parallel will be used, comes to a decision after evaluating a couple of aspects (pinning resources, efforts for driver creation).