EMC Ratiation fail when micro SD working(R/W)

Autonomous Machines Jetson & Embedded Systems Jetson Xavier NX
1
  1. Micro SD will cause Over 15dB noise when R/W and will be brought out from IO port (GPIO, Audio, USB), there will be no noise when Micro SD does not have R/W
  2. Try to replace the Micro SD card, different brands and capacities, the noise energy is still the same high, in the near field measurement found that when Micro SD R/W, the entire MB can be measured noise
  3. Strengthen the grounding of the Micro SD port, and try to countermeasures under the Micro SD MB end, but the noise does not drop significantly
    4. Using the development board, with the currently used CPU and measuring R/W Micro SD with near-field Radiation, the over noise can still be measured
5

What’s your test standard on RF interference? For NX dev kit, the RF related certification is included in the package: https://developer.nvidia.com/jetson-xavier-nx-developer-kit-regulatory-and-compliance-documents-p3518

A custom design should consider EMC problem as need. The specific layout and shielding design should are good method if necessary.

6

Dear Trumany, as Kimi mentioned that the Xavier EVK has the same problem. How do you think?
Is there any document we can refer to tune the driving parameter for further testing?

7

What’s your test standard? Dev kit can not guarantee passing your test, all its certs are in compliance doc as said.

8

Hi,

Also, if you want to adjust the drive strength in software.

Auto calibration offsets are configured in prods.dtsi.
Prods dtsi has mode specific nodes to set the auto calibration offsets.

Ex. For mode SDR104

prod_c_sdr104 {

                            prod = <0x00000100 0x00FF0000 0x000B0000

                                    0x000001C0 0x0000E000 0x00004000

                                    0x000001E0 0x0000000F 0x00000002

                                    **0x000001E4 0x20007F7F 0x20007A00>;**

                    };

AUTO_CAL_PD_OFFSET = 7A,
AUTO_CAL_PU_OFFSET = 0

Auto-calibration offsets are set in 2’s complement form. To reduce the drive strength, set 2’s complement of negative values for auto calibration offsets

9

And register offset info for you.

SDMMC_AUTO_CAL_CONFIG_0:

14:8 0x0 NONE AUTO_CAL_PD_OFFSET: 2’s complement offset for pull-down value
6:0 0x0 NONE AUTO_CAL_PU_OFFSET: 2’s complement offset for pull-up value

the final drivestrength will be shown in :

SDMMC_AUTO_CAL_STATUS_0

30:24 X AUTO_CAL_PULLDOWN_ADJ: Pulldown code sent to pads
22:16 X AUTO_CAL_PULLUP_ADJ: Pullup code sent to pads