Level Output Voltage of Clock and Data are greater than 3.0V when measure the Single-end signal of H...

Hi All :
When we make a test of HDMI(Transmitter), the Level Output Voltage of Clock and Data are over 3.0V (the requirement is less than 2.9V and greater than 2.7V),see picture1.So I want to ask that may I change the parameter of TX Driver(like swing,post-emphasis or pre-emphasis) to decrease the amplitude of the Single-end signal.
Thank you

Hi, did you follow the OEM DG to do the HDMI design? Please check the HDMI part of OEM DG to confirm no violations, especially on Rs and pull-downs (Rpd).

Hi,we buy the JETSON TX2 board from your company,so I think the design is no problem,and I don’t know the Rs and Rd that design on your board also. I think can we enhance the drive capability of the transmitter driver through the software? Because there’s a current mode circuit in the transmitter driver of HDMI

So you are using the dev kit and no custom carrier board, right? Please check the content of register SOR_NV_PDISP_SOR_LANE_DRIVE_CURRENT in TRM, it can be programmed to configure the drive strength.

Thank you for replying,I’ll try to program the register SOR_NV_PDISP_SOR_LANE_DRIVE_CURRENT to verify later.In addition,I want to ask you that can I increase the swing of the differential signal via programming the register?

Hi Trumany:

I’m software engineer corporate with @weixin-zheng. I want to know how to write value to register SOR_NV_PDISP_SOR_LANE_DRIVE_CURRENT by linux command, such as devmem2…etc. If this value set in file hardware/nvidia/soc/t18x/kernel-dts/tegra186-soc/tegra186-soc-prod.dtsi as following code fragment? thanks!
I also can read the value by “sudo cat /sys/kernel/debug/tegra_sor1/regs”, right?

95                                 /* HDMI prod-settings for fall-back to old DT config
496                                  * when prod_list_hdmi_soc/board are not found */
497                                 prod_c_54M {
498                                         prod = <
499                                                 0x0000058c 0x0f0f0f00 0x05050000
500                                                 0x00000590 0x00f01f00 0x00301F00
501                                                 0x00000598 0xff000ff0 0x38000440
502                                                 0x00000138 0xffffffff 0x333A3A3A
503                                                 0x00000148 0xffffffff 0x00000000
504                                                 0x000005a0 0x0040ff00 0x00000000
505                                                 0x000005a8 0xff000000 0x54000000
506                                         >;
507                                 };
508                                 prod_c_75M {
509                                         prod = <
510                                                 0x0000058c 0x0f0f0f00 0x05050100
511                                                 0x00000590 0x00f01f00 0x00301F00
512                                                 0x00000598 0xff000ff0 0x38000440
513                                                 0x00000138 0xffffffff 0x333A3A3A
514                                                 0x00000148 0xffffffff 0x00000000
515                                                 0x000005a0 0x0040ff00 0x00400000
516                                                 0x000005a8 0xff000000 0x44000000
517                                         >;
518                                 };
519                                 prod_c_150M {
520                                         prod = <
521                                                 0x0000058c 0x0f0f0f00 0x05050300
522                                                 0x00000590 0x00f01f00 0x00301F00
523                                                 0x00000598 0xff000ff0 0x38000440
524                                                 <b>0x00000138 0xffffffff 0x373A3A3A</b>
525                                                 0x00000148 0xffffffff 0x00000000
526                                                 0x000005a0 0x0040ff00 0x00400000
527                                                 0x000005a8 0xff000000 0x34000000
528                                         >;
529                                 };
530                                 prod_c_300M {
531                                         prod = <
532                                                 0x0000058c 0x0f0f0f00 0x05050300
533                                                 0x00000590 0x00f01f00 0x00301F00
534                                                 0x00000598 0xff000ff0 0x38000440
535                                                 0x00000138 0xffffffff 0x333D3D3D
536                                                 0x00000148 0xffffffff 0x00000000
537                                                 0x000005a0 0x0040ff00 0x00404000
538                                                 0x000005a8 0xff000000 0x34000000
539                                         >;
540                                 };

Yes, if you want to modify the swing,post-emphasis or pre-emphasis, please try it in prod setting.

@WayneWWW @Trumany
Hi,we have changed the register SOR_NV_PDISP_SOR_LANE_DRIVE_CURRENT ,but it only optimizes about 30mV (when SOR_NV_PDISP_SOR_LANE_DRIVE_CURRENT is 0x373a3a3a,the single ended low level output voltage of Data0+ is 3.04V,and when we changes the register to the max value 0x47474747,the Vl is 3.01V,and we also change the register to 0x17171717,and the Vl is 3.1V),so is that any other register we can change to make the Vl to 2.7-2.9V.
Also ,I saw the 《TX1/TX2 Developer Kit Carrier Board》,what are the functions of these 600ohm resistors and does they have any influence on the signal level?
Thank you

Those are beads of 600ohm@100Mhz. Please check HDMI part of OEM DG to get more info. Seems you need to adjust value of Rs as said in OEM DG: 0ohm is acceptable if the design passes the HDMI2.0 HF1-9 test. Otherwise, adjust the RS value to ensure the HDMI2.0 tests pass: Eye diagram, Vlow test and HF1-9 TDR test