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 following figure shows a rendering of the USB-SD-Mux.
This figure shows the following areas:
This area is the Mico-SD-Card shaped DUT connector of the USB-SD-Mux.
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.
micro SD card slot
Micro USB connector