Author Topic: What are the recommended pull-up resistors when using an SD card  (Read 14088 times)

Offline mhoneywill

  • Full Member
  • ***
  • Posts: 172
    • View Profile
What are the recommended pull-up resistors when using an SD card
« on: December 20, 2010, 11:34:32 AM »
Hi Mark,

I'm looking at incorporating a micro SD card into a board revision. I've looked at the schematics for the Luminary Eval boards and

1. The LM3S6965 board has pullups on pins 1 and 8 (which are DAT2 and DAT1) this makes sense as they are unused in SPI mode
2. Also the Micro SD card on the IDM_L35_RDK kit has a pull-up on the /CS line
3. You say in this post http://www.utasker.com/forum/index.php?topic=786.msg3486#msg3486 that you also needed to ad a pull up to the MISO line.

So in all I need 4 pull ups does that make sense to you?

Cheers

Martin

Offline mark

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 2955
    • View Profile
    • uTasker
Re: What are the recommended pull-up resistors when using an SD card
« Reply #1 on: December 20, 2010, 02:08:54 PM »
Hi Martin

I would tend to use the 4 pull-ups. Sometimes the unused SD card pins are left open and sometimes it works without MISO pull-up (sometimes I did find this necessary though). Certain ones can always be left off later if they prove to be unnecessary.

Regards

Mark