TABLE OF CONTENTS

• Overview
• Accessing Sensor Data
• Sensor Data Files
• Interpretation

Overview

The Cardshark’s USB-PD interface allows the system to monitor power delivery parameters through sensor readings provided by a hardware monitoring (hwmon) driver. Once the TPS25762 driver is loaded via jetpack-tools, it creates a hwmon device under the sysfs hierarchy. Note that the specific hwmon device (e.g., hwmon3) may vary between systems.
Identifying the Correct hwmon Device

To determine which hwmon device corresponds to the USB-PD interface, list the devices under /sys/class/hwmon:

ls -l /sys/class/hwmon

A typical output might be:

lrwxrwxrwx 1 root root 0 Feb 19 10:23 hwmon0 -> ../../devices/platform/pwm-fan/hwmon/hwmon0
lrwxrwxrwx 1 root root 0 Feb 19 10:23 hwmon1 -> ../../devices/platform/bus@0/c240000.i2c/i2c-1/1-0040/hwmon/hwmon1
lrwxrwxrwx 1 root root 0 Feb 19 10:23 hwmon2 -> ../../devices/platform/bus@0/39c0000.tachometer/hwmon/hwmon2
lrwxrwxrwx 1 root root 0 Feb 19 10:23 hwmon3 -> ../../devices/platform/bus@0/c240000.i2c/i2c-1/1-0022/hwmon/hwmon3
lrwxrwxrwx 1 root root 0 Feb 19 10:23 hwmon4 -> ../../devices/platform/soctherm-oc-event/hwmon/hwmon4

../../devices/platform/bus@0/c240000.i2c/i2c-1/1-0022/hwmon/...

Accessing Sensor Data

To view the sensor data, you use commands to view their contents such as:

cat /sys/class/hwmon/hwmon3/curr1_input
cat /sys/class/hwmon/hwmon3/curr1_label
cat /sys/class/hwmon/hwmon3/in0_input
cat /sys/class/hwmon/hwmon3/in0_label
cat /sys/class/hwmon/hwmon3/in1_input
cat /sys/class/hwmon/hwmon3/in1_label

Sensor Data Files

Within the correct hwmon device directory (e.g., /sys/class/hwmon/hwmon3), you will typically find the following files:

• curr1_input: Contains the raw current sensor reading (e.g., 184).
• curr1_label: Provides the label for the current sensor (e.g., “Vbus”).
• in0_input: Contains the raw reading for the first voltage sensor (e.g., 5096).
• in0_label: Provides the label for the first voltage sensor (e.g., “Vbus”).
• in1_input: Contains the raw reading for the second voltage sensor (e.g., 16320).
• in1_label: Provides the label for the second voltage sensor (e.g., “Vin”).

Interpretation

Files ending with *_input provide the numeric sensor readings (such as voltage in millivolts or current in milliamps), while the corresponding *_label files offer descriptive names for the sensors. In this example:

• The current sensor reads 184 and is labeled Vbus.
• The first voltage sensor reads 5096 and is labeled Vbus.
• The second voltage sensor reads 16320 and is labeled Vin.
• These readings help monitor the USB-PD interface’s power conditions on the Cardshark.