HOW to Increase GNNS timing module on Xavier?

Autonomous Machines Jetson & Embedded Systems Jetson AGX Xavier
1

Hi,I did not find the 1ppS interface on Xavier，HOW to Increase GNNS timing module?Thank you！

2

Does it about GPS problem? Xavier module didn’t have GPS module.

3

Yes，Can I connect an external GPS module?What kind of interface does Xavier support?1pps or other.Thank you！

4

Can I use the gpio35 of J30 as the PPS interface? Or recommend other interfaces

5

You can use any GPIO till its configured as GPIO for getting any GPIO interrupt. But only AON GPIO has direct timestamping event. For other GPIO, you have to rely on the arch timer.
And there is an existing nvpps dirver which is default not enabled I guss. Check for CONFIG_NVPPS for sample implementation.
You can use any GPS controller over USB

Release 32.3 upcoming will be having AON GPIO timestamping event feature in SW

6

Thank you for your reply！
What does “AON” mean？In which document can I find？

7

For the TX2/Xavier there have two group’s GPIO one is main another call AON.

Have a check below file for the GPIO define.

…/kernel/kernel-4.9/arch/arm/boot/dts/include/dt-bindings/gpio/tegra186-gpio.h

8

AON is always on island of the chip.

9

Hi chengjingbo,

You can use GPIO as PPS interface.

Here are the steps:

  1. Enable CONFIG_PPS and CONFIG_PPS_CLIENT_GPIO configs in kernel
  2. Add Device tree node in kernel dtb anywhere inside dtb like following:
    pps {
    gpios = <&tegra_aon_gpio TEGRA194_AON_GPIO(AA, 0) GPIO_ACTIVE_LOW>;
    compatible = “pps-gpio”;
    assert-falling-edge;
    status = “okay”;
    };
    You can choose any GPIO present on 40-pin (J30) for this purpose.
    Compile, update dtb and flash system with above changes.

After system boots, you will see sysfs node for PPS.
$ ls /sys/class/pps/pps0/
Whenever interrupt occurs on falling edge of signal, timestamp will be captured and seen using:
cat /sys/class/pps/pps0/assert

If you want events to generate on rising edge of signal then remove assert-falling-edge; property from device node.
Let me know if you need any help.

Thanks,
Shubhi Garg

10

Hi, Shubhi, thanks for your pointing out method to activate gps pps signal. Could you please further explain how to access the GPS $GPRMC info? Since there are several groups of uart ports on Xavier, which one should be chosen to connect to the uart-tx of external module, or any of them works fine?

11

Hi,
You can connect to UART present on 40-pin connector. In the UART console of 40-pin /dev/ttyUSBx (x=0,1…) you can access GPS.

12

Hi,

I decompiled my kernel dtb and added the pps block to the gpio@c2f0000 block in my dts file. However, I get an error when I try to recompile into dtb at this line:

gpios = <&tegra_aon_gpio TEGRA194_AON_GPIO(AA, 0) GPIO_ACTIVE_LOW>;

What am I doing wrong?

13

Hi bobsaccamano,

Please open a new topic for your issue. Thanks