TX1 SD card signals voltage

On the TX1 OEM data sheet it shows that the internal pullups for the SD card data line are 3.3V/1.8V.

it is also say that for fast data rate you need to have the 1.8V pullups.

how do i change the Sd card data lines to work on the 1.8V ?

i can;t find the info in the datasheets

thank you

Hi, please read Tegra X1 (SoC) Technical Reference Manual in DLC, there is a chapter of SD3.0 Signal Voltage Switching in it. https://developer.nvidia.com/embedded/downloads

Thank you Trumany,
I connected the scope to one of the data line and it looks that the voltage drops from 3.3V to 1.8V as it should

but the larger SD card, 400GB and above does not work.

Is there a reason that larger SD card would not work?

Thank you

Hi, capacity is up to 2TB, it looks more like SD card compatible problem, did you test different brands cards?

Hi, Yes i tried many micro SD cards.

I had the data and clock lines length match in the layout, verify the change from 3.3V to 1.8V and located the SD card connector as close as possible to the TX1 connector.

right now i don’t have too many options left.
my thoughts are that the traces of 4.3 mils are too thin, or that there is some interference from a clock signal on the board.

but i did manage to use 256GB microSD cards with no problem.

i there a way to get the TX1 to sweep the frequencies and write/read speed and output a report ?
i assume that clock speed is different for different card volume.

the other option is a driver issue, but on the evaluation board is works with the full size sd card adapter for the same microSD cards i tested.

any thoughts ?

Thank you

Hi eladeshkol,

If you want to limit to only 1.8v, you could add “only-1-8-v” in your sdhci device tree.

You could refer to below document for those properties. Please download kernel source code and refer it.


Thank you very much WayneWWW