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May 2012

USB Host Capability

Micro-Robotics has developed a USB host driver that allows you to plug in USB Flash Drives and other Mass Storge Devices. The new Application Board 3 incorporates a USB Host interface.

Summary of Features

  • Hardware : The USB Host interface is based on the MAX3421E device. The interface circuit is quite simple.
  • VM2 channels used : The interface uses SPI Bus 2, which it shares transparently with the Ethernet and Memory Card (SD/SDHC) interfaces.
  • Speed : The hardware supports USB 2.0 full speed but not high speed, so the raw data rate is 12 Mbits/sec.
  • One device only : we do not support USB hubs, so the memory device must be connected directly to the USB socket
  • Devices supported : we have tested file system read/write operation on several different types of USB Flash drive, SD card holder and multipurpose card reader.
  • File Systems Supported : FAT and FAT32 file systems are supported.
  • Venom Interface : A file system object for a USB device is created by code like this:
    MAKE usbfs filesystem("USB")
    After that, use of the file system is very similar to memory cards.
  • Application Board 3 incorporates a USB Host interface and has a USB Type A receptacle so you can plug in USB Flash drives and other USB Mass Storage Devices. A Micro-SD memory card holder is also fitted to the board for fixed storage. File systems on both media can be supported concurrently.