user61276: Is it possible to read a microSD card (on a breakout) through the USB port on the arduino? or perhaps another USB port I could attach to the breakout?  Basically, I would like to read data off the card with my laptop without having to go and remove it each time! 

user31105: It would be very useful, but afaik this is not possible, since the Arduino sketch you write communicates to the PC via the serial interface only.
The IDE/Arduino driver can use the USB to write your sketch and use the USB for communicating, but for sketches the USB (as direct medium) is not possible.
The SD card will not show up as a specific drive/map/folder on your PC.
Since you want to read the SD card, write in your sketch code to transmit the file(s) you want to send to the PC, to transfer them by UART, and on the PC write a program that reads the serial port and processes it.

user38721: In general that's possible. But you can't read the sd card through the arduino's usb port. Instead you have to read the sd card via another protocol, e.g. SPI (look for the apropriate library) and send it to the pc via serial. You'll need software on the pc side to write the content that was read from the arduino to a file.
Take a look at the SD card tutorial to see how to read it.

61276: <p>Is it possible to read a microSD card (on a breakout) through the USB port on the arduino? or perhaps another USB port I could attach to the breakout?  Basically, I would like to read data off the card with my laptop without having to go and remove it each time! </p>
 31105: <p>It would be very useful, but afaik this is not possible, since the Arduino sketch you write communicates to the PC via the serial interface only.</p>

<p>The IDE/Arduino driver can use the USB to write your sketch and use the USB for communicating, but for sketches the USB (as direct medium) is not possible.</p>

<p>The SD card will not show up as a specific drive/map/folder on your PC.</p>

<p>Since you want to read the SD card, write in your sketch code to transmit the file(s) you want to send to the PC, to transfer them by UART, and on the PC write a program that reads the serial port and processes it.</p>
 38721: <p>In general that's possible. But you can't read the sd card through the arduino's usb port. Instead you have to read the sd card via another protocol, e.g. SPI (look for the apropriate library) and send it to the pc via serial. You'll need software on the pc side to write the content that was read from the arduino to a file.</p>

<p>Take a look at the <a href="https://randomnerdtutorials.com/guide-to-sd-card-module-with-arduino/" rel="nofollow noreferrer">SD card tutorial</a> to see how to read it.</p>
