Micro Digital Inc

smxUSBH™ (Host Stack), smxUSBD™ (Device Stack), smxUSBO™ (OTG)

Compatible Operating Systems: SMX® RTOS, Easily ported to proprietary environments, stand alone, and other RTOS’s
USB Support: USB Host, Device, On-The-Go

smxUSBH (Host Stack), smxUSBD (Device Stack), and smxUSBO (On The Go) are robust solutions for adding USB connectivity to embedded devices. Written in ANSI-C, their clean, modular design makes USB implementation surprisingly easy. Developed explicitly for use in embedded devices, smxUSB has small code and RAM footprints. For smxUSBH (Host), with the mass storage class driver, typical code and RAM sizes are 29KB and 6KB, respectively, including a typical driver for the USB host controller. For smxUSBD (Device) with mass storage emulation, typical code and RAM sizes are 15KB and 6KB, respectively, including a typical driver for the USB device controller. smxUSBO (OTG) adds 7KB code.

While optimally supported by SMX® RTOS, smxUSB is portable and can be easily ported to proprietary environments, other RTOSs, and is often used standalone. Read and write performance are excellent, and are listed in the product data sheets.

Available with smxUSBH, or separately, are host class drivers including audio, mass storage, HID, printer, hub, serial, mouse, keyboard, CDC ACM (modem), RFID, Serial USB to serial adapter, USB to Ethernet adapter, RFID, Sierra wireless, video, and WiFi with WPA. With smxUSBD are device class emulators for serial, multiport serial, mouse, mass storage, audio with MIDI, video, MTP/PTP, Ethernet over USB (RNDIS), Device Firmware Upgrade (DFU), and composite. Device class emulators are Windows compatible and do not require custom Windows drivers, except multiport serial and DFU which are included.

Used with the smxFS, DOS/FAT-compatible file system, smxUSBH (Host) supports mass storage devices such as Thumb Drives and USB hard drives. smxUSBD (Device) used with smxFS turns an embedded device into a Windows-compatible USB Drive. Both solutions provide an easy way of transferring files to and from an embedded device.


  • Small code and RAM foot print.
  • Easily adapted to proprietary environments, commercial RTOSs, or standalone use. Pre-integrated with SMX RTOS.
  • Full support for many USB host and device controllers, including those on popular processor chips.
  • With smxFS (file system), smxUSBH enables easy USB Thumb Drive support.
  • smxUSBD enables easy connection to Windows PCs without requiring custom Windows drivers




  • Support for USB 1.1, USB 2.0 and OTG
  • Full source code in ANSI-C with 90 days of support and maintenance.
  • Support for wide range of 16 and 32 bit processors: ARM, Cortex, Blackfin, ColdFire, PowerPC, RX, SH, x86 and others.
  • Supplied with complete, easy-to-read manuals, which include detailed sections on porting.
  • Support for a wide range of processor on-chip USB controllers, external USB controllers such as the ST-Ericsson (NXP) ISP family, Maxim, Synopsys, and OHCI, UHCI and EHCI compliant controllers.




Wide range of consumer and embedded devices that can benefit from USB connectivity.

Contact Information

Micro Digital Inc

2900 Bristol Street
Suite G 204
Costa Mesa, CA, 92626

tele: 714.437.7333
fax: 714.432.0490

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