USB-SD-Mux Overview

Theory Of Operation

The USB-SD-Mux multiplexes a micro SD card between a host and a Device under Test (DUT).

The host is a computer that controls the operation of the USB-SD-Mux and is able to access the micro SD card via USB.

The DUT is the embedded board that you want to connect to a Micro SD-Card.

The micro SD card is inserted into the card slot on the USB-SD-Mux. The USB-SD-Mux is inserted into the micro SD card slot on the DUT

+-------+     +--------------+     +-------+
|       |     |              |     |       |
|  DUT  +----->  USB-SD-Mux  <-----+ Host  |
|       |     |              |     |       |
+-------+     +------+-------+     +-------+
                     |
                     |
              +------v-------+
              |              |
              |   SD card    |
              |              |
              +--------------+

When the USB-SD-Mux is switched into host-mode using the control software the following steps are executed:

  • The micro SD card is electrically disconnected from the DUT.

  • The control software waits 1 second for the DUT power down.

  • The micro SD card is electrically multiplexed to the card reader on the USB-SD-Mux and the card-inserted signal on the card reader is toggled.

  • The host system will detect that a micro SD card has been inserted into the USB-SD-Mux's card slot and start detection.

  • On successfull detection the card will be provided as a block device depending on your systems settings.

When the USB-SD-Mux is switched into DUT mode using the control software the following steps are executed:

  • The micro SD card is electrically disconnected from the USB-SD-Mux' card reader.

  • The control software waits 1 second for the DUT power down.

  • The micro SD card is electrically multiplexed to the DUT conntector on the USB-SD-Mux.

Electronics

The following figure shows a rendering of the USB-SD-Mux.

_images/product-operation-overview.svg.png

Front- and Back-View of the USB-SD-Mux

This figure shows the following areas:

  1. This area is the Mico-SD-Card shaped DUT connector of the USB-SD-Mux.

  2. Three status LEDs are arranged in this area:

    • 'DUT' and 'HOST' show to which side the SD card is multiplexed. If both LEDs off signal the SD card being disconnected.

    • The 3rd LED is active when the USB-SD-Mux is powered.

  3. micro SD card slot

  4. Micro USB connector