Hardware Access Guide

epc670 ToF HAT+ provides several low-level hardware interfaces that can be accessed directly from Linux. These interfaces are primarily intended for diagnostics, maintenance, manufacturing, and advanced development.

This guide explains how to access:

On-board temperature sensors via hwmon
On-board SPI NOR flash storage via MTD
Sensor internal temperature via driver hwmon
Sensor registers via debugfs

Temperature Monitoring (Board Sensors via hwmon)

The epc670 ToF HAT+ features two board-level temperature sensors placed near the illumination LEDs. They monitor thermal conditions around heat-generating components.

These sensors are exposed through the Linux hwmon subsystem.

Identify the correct hwmon devices

# List available hwmon devices
ls /sys/class/hwmon/

# Locate the device
grep . /sys/class/hwmon/hwmon*/name

Expected entry:

tmp112

Read current temperatures

cat /sys/class/hwmon/hwmon1/temp1_input
cat /sys/class/hwmon/hwmon2/temp1_input

Values are reported in millidegree Celsius (m°C).

Example:

42125  →  42.125 °C

Temperature Monitoring (Sensor Internal via Driver hwmon)

The epc670 sensor itself integrates multiple internal temperature sensors. These are exposed by the driver through a separate hwmon interface.

Locate the device

grep . /sys/class/hwmon/hwmon*/name

Expected entry:

epc670

Available channels

Channel	Label
0	epc670_temp_sensor_0
1	epc670_temp_sensor_1
2	epc670_temp_sensor_2
2	epc670_temp_sensor_3

Read temperatures

cd /sys/class/hwmon/hwmonX

paste temp*_label temp*_input

For more info, please visit The hwmon Interface

Sensor Register Access (Driver debugfs)

The debugfs interface allows low-level register access to the epc670 sensor for debugging and bring-up.

All epc670 debug files are located at:

/sys/kernel/debug/epc670/

If the directory is missing, mount debugfs:

sudo mount -t debugfs none /sys/kernel/debug

Available interfaces

File	Purpose
read_reg	Read one or more sensor registers
write_reg	Write sensor registers
dump	Dump full register map

Example: Read registers

echo "0xA0 3" | sudo tee /sys/kernel/debug/epc670/read_reg
sudo cat /sys/kernel/debug/epc670/read_reg

Example: Write registers

echo "0xA0 0x12 0x34 0x56" | sudo tee /sys/kernel/debug/epc670/write_reg

Warning

Writing invalid values may damage the device or cause undefined behavior.

For full documentation, see: The DebugFS Interface

Device Nodes Overview 

Path	Purpose
`/dev/videoX`	Frame streaming
`/dev/epc670_subdev`	Sensor control
`/sys/class/hwmon/`	Temperature monitoring
`/sys/kernel/debug/epc670/`	Register debugging
`/mnt/spi_flash`	Block-mapped flash

Runtime Nodes Overview 

Path	Purpose
`/run/epc670/video`	Symlink to correct frame streaming video node
`/run/epc670/media`	Symlink to correct media device node
`/run/epc670/subdev`	Symlink to `/dev/epc670_subdev`, sensor control

When to Use Each Interface 

Task	Interface	Path
Monitor LED board temperature	hwmon (temp112)	`/sys/class/hwmon/hwmonX`
Monitor sensor internal temperature	driver hwmon	`/sys/class/hwmon/hwmonY`
Debug sensor configuration	debugfs	`/sys/kernel/debug/epc670/`
Store calibration data	SPI NOR flash	`/mnt/spi_flash`
Capture frames	V4L2 video node	`/dev/videoX`