Conn_SD Write Protect and Detect Switch Pins?



  • Hi all,
    Here's my problem:
    I'm making a PCB that includes an SD card reader (not microSD) that I plan to connect to the Conn_SD using a 10 pin ribbon wire. I have outlined the specific connection on the duet schematic in green for clarity.

    DuetSDConn.jpg

    Now the reader I plan to use has two additional switches on it: a write protect switch and a detect switch. This picture shows the reader component's PCB pattern. I outlined solder paste locations in gold, and the switches in question in red.

    SDReaderSwitches.jpg

    I'm wondering if the duet needs me to connect either of these switches to a specific pin from the Conn_SD pin array in order for the duet to read/write to the SD. Can I ignore the switches and just worry about tracing the 9 SD pins? Or do I connect VCC to the detect switch and just leave it high?

    Any assistance would be appreciated, thanks.


  • administrators

    RRF doesn't need the card detect or write protect pins for external SD cards. It could support the card detect pin with a small firmware change.



  • @dc42 So in the event I'm using 5V for VCC, the extra pin on the Conn_SD board (since the SD card only needs nine pins) would be the 3.3V?


  • administrators

    @bkolligs said in Conn_SD Write Protect and Detect Switch Pins?:

    @dc42 So in the event I'm using 5V for VCC, the extra pin on the Conn_SD board (since the SD card only needs nine pins) would be the 3.3V?

    Do you mean that your SD card reader includes its own 5V to 3.3V regulator, and you are powering it from 5V? If so, check that your SD card reader doesn't have other electronics on it, such as level-shifters.



  • @dc42 In the event that we did want to allow detect pin functionality what pin would we route that switch to? What firmware change would you need to make?
    I think it'd be nice if the system would prompt the user with a "SD card inserted" type message.



  • @dc42 I will be powering the SD card with 3.3V, so I don't think I'd need to use the 5V pin. Also, I am assuming the duet uses SPI based off the pin names.


  • administrators

    @jckray said in Conn_SD Write Protect and Detect Switch Pins?:

    @dc42 In the event that we did want to allow detect pin functionality what pin would we route that switch to? What firmware change would you need to make?
    I think it'd be nice if the system would prompt the user with a "SD card inserted" type message.

    You would have to pick a pin on the expansion board connector that you were not otherwise using. The card detect pins are listed in file Pins_DuetNG.h.



  • @dc42 So if we did want to do that then we could write our own firmware change to allow the detect functionality?



  • @dc42 Where is that header file located in the git repo? I would like to take a look.


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