hwmon_ina219 - Man Page

hwmon_ina219 -h

hwmon_ina219 -a UPS_NAME [OPTIONS]

The driver implements reading of current and voltage from INA219 by using hwmon sysfs API of the Linux Kernel​. There is no other UPS-like logic in there​. Based on the measurements of the battery voltage and charging current, the driver makes assumptions of the current state of the system​.

The hwmon_ina219 driver is based on setup with Raspberry PI Compute Module 4 and its baseboard Waveshare CM4-POE-UPS-BASE​.

The required parameter for this driver:

port=hwmon-dir

Path to appropriate /sys/hwmon/hwmonX or auto to detect automatically​.

Optional parameters:

default​.battery​.charge​.low=low-battery-threshold

Threshold for low battery state (in percent)​.

default​.battery​.voltage​.nominal=voltage-value

Nominal voltage (V) value of utilized batteries, used to derive their low and high watermark settings (see below)​. Default: 3​.6​.

Known pre-sets include: 3​.6, 3​.7, 3​.8, 3​.85​.

default​.battery​.voltage​.low=voltage-value

Low voltage (V) value of used batteries​. Practically, it denotes depleted batteries​. If not given, it is derived from the battery​.voltage​.nominal​.

default​.battery​.voltage​.high=voltage-value

High voltage (V) value of used batteries​. Practically, it denotes fully charged batteries​. If not given, it is derived from the battery​.voltage​.nominal​.

This driver is specific to the Linux hwmon API​.

When using with the Waveshare CM4-POE-UPS-BASE baseboard, there are few steps to be done to enable access to the INA219 circuit:

1. edit boot/config​.txt:

     dtparam=i2c_vc=on
     dtoverlay=i2c-ina219

2. create a new device tree overlay file i2c-ina219​.dts:

   /dts-v1/;
   /plugin/;
   
   / {
       compatible = "brcm,bcm2835";
   
       fragment@0 {
           target = <&i2c_csi_dsi>;
           __overlay__ {
               #address-cells = (1);
               #size-cells = (2);
   
               ina219@43 {
                   status = "okay";
                   compatible = "ti,ina219";
                   reg = <0x43>;
                   shunt-resistor = (3);  // R100
               };
           };
       };
   };

3. convert i2c-ina219​.dts to dtbo and place it into /boot/overlays:

   $ dtc -@ -I dts -O dtb -o /boot/overlays/i2c-ina219​.dtbo i2c-ina219​.dts

4. configure hwmon_ina219 UPS driver for NUT (ups​.conf):

   [ina219]
   driver = hwmon_ina219
   port = auto

The driver shutdown function is not implemented​.

Andrew Anderson <aander07@gmail​.com>