White Papers

How to Interface a USB Flash Drive to a Microcontroller

How to Design an Embedded System with USB Flash Drive Support

The removable USB flash drive is a key technology in the embedded computing world. Among other things, it can be used to store and transfer logged data, back up a device’s settings, or be a vehicle to update a deployed device’s firmware. When you need to transfer data from a microcontroller-based embedded system to a PC (or vice versa), using a portable memory device, like a USB flash drive, is a convenient method, especially when transferring data over a network is not possible or desirable.

Although USB flash drives are easy to use, designing a microcontroller-based embedded system that supports the use of these devices can be a challenging task, especially when you don't know what you don't know. This 17-page white paper provides embedded systems designers with the key concepts and considerations needed to successfully incorporate a USB host into a microcontroller-based embedded design, such that USB flash drives can be used for a host of applications.

Table of Contents

1. Introduction
2. An Overview of the Universal Serial Bus (USB)
3. Designing the System
   1. Make/Buy
   2. Compliance Testing
   3. Implementation Overview
   4. USB Host Controller Choices
   5. USB Software Support
4. Designing Custom USB Hardware
   1. USB Connectors
   2. Power Supplies
   3. Resets & Brownout
   4. Electromagnetic Interference (EMI)
   5. Controlled Impedance
5. Example Host Controller Solutions
   1. Example Bolt-On Host Controller
   2. Example Built-In Host Controller
6. Implementing the Embedded Firmware
   1. The USB Flash Drive File System
   2. Handling Surprise Removal and Power Loss
   3. File System Licensing
7. About Datakey
8. Conclusion
9. Glossary
10. References