Strato Pi Max driver kernel module

Raspberry Pi OS Kernel module for Strato Pi Max.

It gives access to all Strato Pi Max functionalities and configuration options via sysfs virtual files.

Compile and Install

For installation on Ubuntu read this.

Make sure your system is updated:

sudo apt update
sudo apt upgrade

If you are using a 32-bit OS, add to /boot/firmware/config.txt (/boot/config.txt in older versions) the following line: [why?]

arm_64bit=0

Reboot:

sudo reboot

After reboot, install git and the Raspberry Pi kernel headers:

sudo apt install git raspberrypi-kernel-headers

Clone this repo:

git clone --depth 1 https://github.com/sfera-labs/strato-pi-max-kernel-module.git

Make and install:

cd strato-pi-max-kernel-module
make clean
make
sudo make install

Compile the Device Tree and install it:

dtc -@ -Hepapr -I dts -O dtb -o stratopimax.dtbo stratopimax.dts
sudo cp stratopimax.dtbo /boot/overlays/

This overlay, amongst the different peripherals, configures the secondary SD interface to use the sdhost controller, so that sdio is available for WiFi on CM units equipped with it.

To load the driver at boot, add to /boot/firmware/config.txt (/boot/config.txt in older versions) the following line:

dtoverlay=stratopimax

Optionally, to be able to use the /sys/class/stratopimax/ files not as super user, create a new group "stratopimax" and set it as the module owner group by adding an udev rule:

sudo groupadd stratopimax
sudo cp 99-stratopimax.rules /etc/udev/rules.d/

and add your user to the group, e.g. for user "pi":

sudo usermod -a -G stratopimax pi

Reboot:

sudo reboot

Usage

After loading the module, you will find all the available devices under the path /sys/class/stratopimax/.

The following paragraphs list all the devices (directories) and properties (files) coresponding to Strato Pi Max's and its expansion boards' features.

You can write and/or read these files to configure, monitor and control your Strato Pi Max. The kernel module will take care of performing the corresponding GPIO or I2C operations.

Properties with the _config suffix represent configuration parameters that are saved and retained across power cycles.
Configuration parameters marked with the CR attribute (see the attributes table below) take effect immediately when set. Conversely, parameters with the C attribute store the value to be applied during the next power-up by copying it to the corresponding "runtime" property (same name without the _config suffix).

Note

A power-up occurs when:

• the unit is powered on (main power supply connected);
• a power cycle is explicitly initiated via power/down_enabled; or
• a power cycle is initiated by another process configured to do so (e.g. watchdog timeout expiration).

A software reboot of the compute module does not correspond to a power-up.

This enables configuring settings for the next power cycles, whether after a planned or abrupt shutdown. For example, it allows switching the boot SD card while the compute module is off or having a short watchdog timeout during application runtime, which resets to a longer duration after a power cycle to ensure reliable boot and restart.

All properties' attributes are summarized here:

Attribute	Description
R	Readable
W	Writable
RC	Readable. Cleared when read
WF	Writable only when expansion board is off
C	Configuration value, persisted and retained across power cycles, copied to "runtime" counterpart on power-up
CR	Configuration value, persisted and retained across power cycles, effective immediately

System - /sys/class/stratopimax/system/

File	Description	Attr	Value	Value description
fw_version	Firmware version	R	M.m	Major (M) and minor (m) version
config	Configuration commands	W	R	Restore the factory configuration
sys_errs	System errors flags	RC	MLKJxHGFxDCBA	Bitmap (0/1) sequence. A: system setup failure B: RP2040 failure C: RP2040 reset occurred D: configuration loading/saving error F: RP2040 I2C master failure G: RP2040 I2C slave failure H: RP2040 SPI failure J: USB ports fault K: I/O expanders fault (see ioexp_errs) L: accelerometer fault M: UPS fault x: reserved, set to 0
ioexp_errs	I/O expanders errors flags	RC	GFEDCBA	Bitmap (0/1) sequence. A: I/O expander BU17 fault B: I/O expander BU21 fault C: I/O expander BU22 fault D: I/O expander on expansion board in slot 1 fault E: I/O expander on expansion board in slot 2 fault F: I/O expander on expansion board in slot 3 fault G: I/O expander on expansion board in slot 4 fault

Power cycle - /sys/class/stratopimax/power/

File	Description	Attr	Value	Value description
down_enabled	Delayed power cycle enabling	R	0	Disabled
		R W	1	Enabled. Once enabled cannot be interrupted
down_delay_config	Shutdown delay from enabling	R W CR	1 ... 65535	Value in seconds. Default: 60
off_time_config	Power-off duration	R W CR	1 ... 65535	Value in seconds. Default: 5
up_delay_config	Power-up delay configuration	R W CR	1 ... 65535	Value in seconds. Default: 0
up_backup_config	Configuration for enabling power-up when a power cycle occurs while main power is not available (requires UPS expansion board)	R W CR	0	Power-up only when main power is restored (default)
			1	Power-up even if running on backup power source (UPS battery)
sd_switch_config	SDA/SDB switch configuration on power cycle	R W CR	0	Disabled (default)
			1	Enabled
pcie_switch_config	PCIE on/off toggle configuration on power cycle	R W CR	0	Disabled (default)
			1	Enabled

Watchdog - /sys/class/stratopimax/watchdog/

File	Description	Attr	Value	Value description
enabled	Watchdog enabling	R W	0	Disabled
			1	Enabled
enabled_config	Watchdog enabling configuration	R W C	0	Disabled (default)
			1	Enabled
timeout	Watchdog timeout	R W	1 ... 65535	Value in seconds. Default: 60
timeout_config	Watchdog timeout configuration	R W C	60 ... 65535	Value in seconds. Default: 60
down_delay_config	Automatic power cycle delay configuration when watchdog timeout expires	R W CR	0 ... 65535	Value in seconds. Default: 60
sd_switch_config	SDA/SDB switch configuration on watchdog reset	R W CR	0	Disabled (default)
			1	Switching occurs upon each watchdog reset
			2 ... 65535	Number of consecutive resets (with no heartbeat received in between) before switching occurs. Requires watchdog/enabled_config set to 1
pcie_switch_config	PCIE on/off toggle configuration on watchdog reset	R W CR	0	Disabled (default)
			1	Toggling occurs upon each watchdog reset
			2 ... 65535	Number of consecutive resets (with no heartbeat received in between) before toggling occurs. Requires watchdog/enabled_config set to 1
heartbeat	Watchdog heartbeat update	W	1	Update heartbeat
expired	Watchdog timeout state	R	0	Not expired
			1	Expired

Button - /sys/class/stratopimax/button/

File	Description	Attr	Value	Value description
status	Button state	R	0	Not pressed
			1	Pressed
count	Button presses counter	R	0 ... 255	Rolls back to 0 after 255

Buzzer - /sys/class/stratopimax/buzzer/

File	Description	Attr	Value	Value description
beep	Buzzer beep control	W	0	Off
			1	Steady on
			T_ON T_OFF	Continuos beep T_ON milliseconds on, T_OFF milliseconds off
			T_ON T_OFF REPS	Beep REPS times T_ON milliseconds on, T_OFF milliseconds off
tone	Buzzer beep tone	R W	0 ... 65535	Value in Hz

LEDs - /sys/class/stratopimax/led/

File	Description	Attr	Value	Value description
red	Red LED control	W	0	Off
			1	Steady on
			T_ON T_OFF	Continuos blink T_ON milliseconds on, T_OFF milliseconds off
			T_ON T_OFF REPS	Blink REPS times T_ON milliseconds on, T_OFF milliseconds off
green	Green LED control	W	0	Off
			1	Steady on
			T_ON T_OFF	Continuos blink T_ON milliseconds on, T_OFF milliseconds off
			T_ON T_OFF REPS	Blink REPS times T_ON milliseconds on, T_OFF milliseconds off

USB - /sys/class/stratopimax/usb/

File	Description	Attr	Value	Value description
usb1_enabled	USB1 enabling	R W	0	Disabled
			1	Enabled
usb1_enabled_config	USB1 enabling configuration	R W C	0	Disabled
			1	Enabled (default)
usb1_err	USB1 fault	R	0	OK
			1	Fault
usb2_enabled	USB2 enabling	R W	0	Disabled
			1	Enabled
usb2_enabled_config	USB2 enabling configuration	R W C	0	Disabled
			1	Enabled (default)
usb2_err	USB2 fault	R	0	OK
			1	Fault

SD Cards Switch - /sys/class/stratopimax/sd/

File	Description	Attr	Value	Value description
sd_main_enabled	Main SD interface enabling	R W	0	Disabled
			1	Enabled
sd_main_enabled_config	Main SD interface enabling configuration	R W C	0	Disabled
			1	Enabled (default)
sd_sec_enabled	Secondary SD interface enabling	R W	0	Disabled
			1	Enabled
sd_sec_enabled_config	Secondary SD interface enabling configuration	R W C	0	Disabled (default)
			1	Enabled
sd_main_routing	Main SD routing control	R W	A	Main SD interface routed to SDA, secondary SD interface to SDB
			B	Main SD interface routed to SDB, secondary SD interface to SDA
sd_main_routing_config	Main SD routing configuration	R W C	A	Main SD interface routed to SDA, secondary SD interface to SDB (default)
			B	Main SD interface routed to SDB, secondary SD interface to SDA

PCIE interface - /sys/class/stratopimax/pcie/

File	Description	Attr	Value	Value description
enabled	PCIE enabling	R W	0	Disabled
			1	Enabled
enabled_config	PCIE enabling configuration	R W C	0	Disabled
			1	Enabled (default)

Power Supply Input - /sys/class/stratopimax/power_in/

File	Description	Attr	Value	Value description
mon_v	Power supply voltage monitor	R	V	Value in mV
mon_i	Power supply current drain monitor	R	V	Value in mA

Fan - /sys/class/stratopimax/fan/

File	Description	Attr	Value	Value description
temp	Fan controller measured temperature	R	T	Value in °C/100
temp_on	Temperature threshold for fan activation	R W	-12800 ... 12750	Value in °C/100, 0.5°C resolution
temp_off	Temperature threshold for fan deactivation	R W	-12800 ... 12750	Value in °C/100, 0.5°C resolution

Accelerometer - /sys/class/stratopimax/accelerometer/

File	Description	Attr	Value	Value description
accel_x	X-axis acceleration	R	-32768 ... 32767	Raw value (resolution: 14-bit, full scale: ±2 g)
accel_y	Y-axis acceleration	R	-32768 ... 32767	Raw value (resolution: 14-bit, full scale: ±2 g)
accel_z	Z-axis acceleration	R	-32768 ... 32767	Raw value (resolution: 14-bit, full scale: ±2 g)

Secure Element - /sys/class/stratopimax/sec_elem/

File	Description	Attr	Value	Value description
serial_num	Secure element serial number	R	HHHHHHHHHHHHHHHHHH	HEX value

---

Expansion Boards

Expansion Boards configuration - /sys/class/stratopimax/exp_boards/

File	Description	Attr	Value	Value description
sN_enabled	Slot N enabling	R W	0	Disabled
			1	Enabled
sN_enabled_config	Slot N enabling configuration	R W C	0	Disabled
			1	Enabled
sN_type	Slot N expansion board type	R	2	Uninterruptible Power Supply
			3	CAN and dual RS-485
			4	RS-232 and RS-485
			5	Industrial digital I/O

Below are the devices corresponding to each expansion board typology.

For expansion boards that can be installed on multiple slots, devices names have a _s<n> suffix denoting their slot number (1 to 4).

---

Uninterruptible Power Supply (UPS) Expansion Board

UPS - /sys/class/stratopimax/ups/

File	Description	Attr	Value	Value description
enabled	UPS enabling	R W	0	Disabled
			1	Enabled
enabled_config	UPS enabling configuration	R W C	0	Disabled
			1	Enabled (default)
battery_v_config	UPS battery voltage configuration	R W CR	12000	12 V battery (default)
			24000	24 V battery
battery_capacity_config	UPS battery capacity configuration	R W CR	100 ... 60000	Value in mAh. Default: 800
battery_i_max	UPS battery maximum charging current while at maximum voltage	R W	0	Value automatically derived from capacity (default)
			1 ... 65535	Value in mA. The automatically derived limit still applies if lower than this value
battery_i_max_config	UPS battery maximum charging current while at maximum voltage configuration	R W C	0	Value automatically derived from capacity (default)
			1 ... 65535	Value in mA. The automatically derived limit still applies if lower than this value
down_delay_config	Automatic power cycle timeout configuration when main power source not available	R W CR	0	Disabled (default)
			1 ... 65535	Value in seconds
battery	Power source state	R	0	Running on main power
			1	Running on battery
status	UPS status	R	0	Idle
			1	Detecting battery
			2	Battery disconnected
			4	Charging battery
			5	Battery charged
			6	Running on battery
			8	Battery over-voltage error
			9	Battery under-voltage error
			10	Charger damaged
			11	Unstable
charger_mon_v	Battery charger output voltage monitor	R	0 ... 65535	Value in mV
charger_mon_i	Battery charger output current drain monitor	R	0 ... 65535	Value in mA

Power Supply Output - /sys/class/stratopimax/power_out/

File	Description	Attr	Value	Value description
vso_enabled	VSO power supply output control	R W	0	Disabled
			1	Enabled
vso_enabled_config	VSO power supply output configuration	R W C	0	Disabled
			1	Enabled (default)

---

SuperCaps UPS Expansion Board

UPS - /sys/class/stratopimax/ups/

File	Description	Attr	Value	Value description
enabled	UPS enabling	R W	0	Disabled
			1	Enabled
enabled_config	UPS enabling configuration	R W C	0	Disabled
			1	Enabled (default)
down_delay_config	Automatic power cycle timeout configuration when main power source not available	R W CR	0	Disabled (default)
			1 ... 65535	Value in seconds
backup	Power source state	R	0	Running on main power
			1	Running on backup power
status	UPS status	R	0	Idle
			4	Charging
			5	Charged
			6	Running on backup power
			10	Fault
			11	Unstable

---

Industrial Digital I/O Expansion Board

Digital inputs - /sys/class/stratopimax/digital_in_s<n>/

File	Description	Attr	Value	Value description
inN_wb_config	Input N Wire-break detection configuration	R WF CR	0	Disabled (default)
			1	Enabled
inN_filter_config	Input N filter configuration	R WF CR	0	50 µs delay (default)
			1	100 µs delay
			2	400 µs delay
			3	800 µs delay
			4	1.6 ms delay
			5	3.2 ms delay
			6	12.8 ms delay
			7	20 ms delay
			8	Filter bypassed
inN	Input N state	R	0	Low
			1	High
inputs	Inputs state combined	R	SSSSSSS	Concatenation of all 7 inputs states
inN_wb	Input N wire-break	R W	0	Not detected (write to clear)
		R	1	Detected (set until cleared)
inputs_wb	Inputs wire-break combined	R	SSSSSSS	Concatenation of all 7 inputs wire-break states
		W	0	clear
alarm_t1	Inputs temperature alarm 1	R W	0	Not active (write to clear)
		R	1	Active (set until cleared)
alarm_t2	Inputs temperature alarm 2	R W	0	Not active (write to clear)
		R	1	Active (set until cleared)
over_temp	Inputs thermal shutdown	R W	0	Not active (write to clear)
		R	1	Active (set until cleared)
fault	Inputs general fault	R	0	Not active
			1	Active

Digital outputs - /sys/class/stratopimax/digital_out_s<n>/

File	Description	Attr	Value	Value description
outN_pp_config	Output N high-side/push-pull mode configuration	R WF CR	0	High-side mode (default)
			1	Push-pull mode
outN_ol_config	Output N open-load detection configuration (only for high-side mode)	R WF CR	0	Disabled (default)
			1	Enabled
join_l_config	Outputs 1-2 (L side terminal block) join configuration (only for high-side mode)	R WF CR	0	Disabled (default)
			1	Outputs 1-2 joined. Configurations and status for output 1 apply to pair
join_h_config	Outputs 4-5 and 6-7 (H side terminal block) join configuration (only for high-side mode)	R WF CR	0	Disabled (default)
			1	Outputs 4-5 and 6-7 joined. Configurations and status for outputs 4 and 6 apply to respective pairs
watchdog_config	Outputs watchdog configuration	R WF CR	0	Disabled
			1	Enabled (default)
watchdog_timeout_config	Outputs watchdog timeout configuration	R WF CR	0	0.9 s (default)
			1	0.45 s
			2	0.15 s
outN	Output N state	R W	0	Low
			1	High
outputs	Outputs state combined	R W	SSSSSSS	Concatenation of all 7 outputs states
outN_ol	Output N open-load	R W	0	Not detected (write to clear)
		R	1	Detected (set until cleared)
outputs_ol	Outputs open-load combined	R	SSSSSSS	Concatenation of all 7 outputs open-load states
		W	0	clear
outN_ov	Output N over-voltage	R W	0	Not detected (write to clear)
		R	1	Detected (set until cleared)
outputs_ol	Outputs over-voltage combined	R	SSSSSSS	Concatenation of all 7 outputs over-voltage states
		W	0	clear
outN_ot	Output N over-temperature	R W	0	Not detected (write to clear)
		R	1	Detected (set until cleared)
outputs_ot	Outputs over-temperature combined	R	SSSSSSS	Concatenation of all 7 outputs over-temperature states
		W	0	clear
outN_ov_lock	Output N over-voltage protection lock	R	0	Not active
			1	Active
outputs_ov_lock	Outputs over-voltage protection lock combined	R	SSSSSSS	Concatenation of all 7 outputs over-voltage protection lock states
outN_ot_lock	Output N over-temperature protection lock	R	0	Not active
			1	Active
outputs_ot_lock	Outputs over-temperature protection lock combined	R	SSSSSSS	Concatenation of all 7 outputs over-temperature protection lock states

---

RS-485 Expansion Boards

Digital inputs - /sys/class/stratopimax/rs485_s<n>/

File	Description	Attr	Value	Value description
echo_config	RS-485 local echo configuration	R W CR	0	Disabled (default)
			1	Enabled

---

Analog Inputs Expansion Board

Analog inputs - /sys/class/stratopimax/analog_in_s<n>/

File	Description	Attr	Value	Value description
avN_enabled_config	Analog voltage input N enabled configuration	R WF CR	0	Disabled
			1	Enabled (default)
avN_bipolar_config	Analog voltage input N bipolar configuration	R WF CR	0	Unipolar: range 0 ... 20 V (default)
			1	Bipolar: range -10 ... 10 V
avN_differential_config	Analog voltage input N (1 or 3) differential configuration	R WF CR	0	Single-ended: AGND is the voltage reference (default)
			1	Differential: voltage difference between input N and N+1
aiN_enabled_config	Analog current input N enabled configuration	R WF CR	0	Disabled
			1	Enabled (default)
aiN_bipolar_config	Analog current input N bipolar configuration	R WF CR	0	Unipolar: range 0 ... 20 mA (default)
			1	Bipolar: range -10 ... 10 mA
av_filter_config	Analog voltage inputs filter configuration	R WF CR	0	Filter configuration register value. Refer to the AD4112 datasheet for details. Default: 1294 (sinc5 + sinc1 filter, 100.2 SPS data rate)
ai_filter_config	Analog current inputs filter configuration	R WF CR	0	Filter configuration register value. Refer to the AD4112 datasheet for details. Default: 1294 (sinc5 + sinc1 filter, 100.2 SPS data rate)
atN_enabled_config	Temperature probe input N enabled configuration	R WF CR	0	Disabled
			1	Enabled (default)
atN_pt1000_config	Temperature probe N type configuration	R WF CR	0	Pt100 (default)
			1	Pt1000
avN	Analog voltage input N value	R	V	Value in mV/100
			8388607	Overrange value
			-8388607	Underrange value
			-8388608	Error
aiN	Analog current input N value	R	V	Value in µA
			8388607	Overrange value
			-8388607	Underrange value
			-8388608	Error
atN	Temperature probe N value	R	V	Value in °C/100
			8388607	Overrange value
			-8388607	Underrange value
			-8388608	Error
v5_fault	5V output fault	R	0	OK
			1	Fault

---

Analog Outputs Expansion Board

Analog outputs - /sys/class/stratopimax/analog_out_s<n>/

File	Description	Attr	Value	Value description
aoN_mode_config	Analog ouput N mode configuration	R WF CR	V	Voltage (default)
			I	Current
aoN	Analog output N value	R W	V	Value, in mV (voltage mode - range 0...10417) or µA (current mode - range 0...20833)
		R	65535	Error
aoN_errs	Analog output N error flags	R	CLT	Bitmap (0/1) sequence. T: over-temperature error L: load error C: common mode error
v5_fault	5V output fault	R	0	OK
			1	Fault