usrp2: added notes about 3rd party sd cards to docs

1 files changed, 12 insertions, 3 deletions

diff --git a/host/docs/usrp2.rst b/host/docs/usrp2.rst
index f0d1e2744..b617fcbf4 100644
--- a/host/docs/usrp2.rst
+++ b/host/docs/usrp2.rst
@@ -11,9 +11,14 @@ Load the images onto the SD card
 Use the usrp2_card_burner.py with caution. If you specify the wrong device node,
 you could overwrite your hard drive. Make sure that --dev= specifies the SD card.
 
-Use the *--list* option to get a list of possible raw devices.
-The list result will filter out disk partitions and devices too large to be the sd card.
-The list option has been implemented on Linux, Mac OS X, and Windows.
+**Warning!**
+It is possible to use 3rd party SD cards with the USRP2.
+However, certain types of SD cards will not interface with the CPLD:
+
+* Cards can be SDHC, which is not a supported interface.
+* Cards can have unexpected timing characteristics.
+
+For these reasons, we recommend that you use the SD card that was supplied with the USRP2.
 
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 Use the card burner tool (unix)
@@ -28,6 +33,10 @@ Use the card burner tool (unix)
     sudo ./usrp2_card_burner.py --dev=/dev/sd<XXX> --fpga=<path_to_fpga_image>
     sudo ./usrp2_card_burner.py --dev=/dev/sd<XXX> --fw=<path_to_firmware_image>
 
+Use the *--list* option to get a list of possible raw devices.
+The list result will filter out disk partitions and devices too large to be the sd card.
+The list option has been implemented on Linux, Mac OS X, and Windows.
+
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 Use the card burner tool (windows)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^