usbhid-ups - Driver for USB/HID UPS equipment


This man page only documents the hardware-specific features of the usbhid-ups driver. For information about the core driver, see nutupsdrv(8).


usbhid-ups brings USB/HID UPS monitoring to NUT on all platforms supporting USB through libusb. It should detect any UPS that uses the HID Power Device Class, but the amount of data will vary depending on the manufacturer and model.

At the present time, usbhid-ups supports:

  • the newer Eaton USB models,

  • all MGE USB models,

  • all Dell USB models,

  • all AMETEK Powervar UPM models,

  • some APC models,

  • some Belkin models,

  • some Cyber Power Systems models,

  • some Powercom models,

  • some PowerWalker models,

  • some TrippLite models.

For a more complete list, refer to the NUT hardware compatibility list, available in the source distribution as data/driver.list, or on the NUT website. You may use the "explore" driver option to gather information from HID UPSes which are not yet supported; see below for details.

This driver is known to work on:

  • most Linux systems,

  • FreeBSD (beta stage) and maybe other *BSD,

  • Darwin / Mac OS X,

  • Solaris 10 and illumos-based distributions.


This driver also supports the following optional settings:

port = string

Some value must be set, typically auto.

This could be a device filesystem path like /dev/usb/hiddev0 but current use of libusb API precludes knowing and matching by such identifiers. They may also be inherently unreliable (dependent on re-plugging and enumeration order). At this time the actual value is ignored, but some port must be there syntactically.

It is possible to control multiple UPS units simultaneously by running several instances of this driver, provided they can be uniquely distinguished by setting some combination of the vendor, product, vendorid, productid, serial, bus and/or device options detailed below.

vendorid = regex
productid = regex
vendor = regex
product = regex
serial = regex

Select a specific UPS, in case there is more than one connected via USB. Each option specifies an extended regular expression (see regex(7) for more information on regular expressions), which must match the UPS’s entire respective vendor/product/serial string (minus any surrounding whitespace), or the whole 4-digit hexadecimal code for vendorid and productid.

Try lsusb(8) or running this NUT driver with -DD command-line argument for finding out the strings to match.


  • -x vendor="Foo.Corporation.*"

  • -x vendorid="051d*" (APC)

  • -x product=".*(Smart|Back)-?UPS.*"

bus = regex

Select a UPS on a specific USB bus or group of buses. The argument is a regular expression that must match the bus name where the UPS is connected (e.g. bus="002" or bus="00[2-3]") as seen in /proc/bus/usb/devices or lsusb(8); including leading zeroes.

device = regex

Select a UPS on a specific USB device or group of devices. The argument is a regular expression that must match the device name where the UPS is connected (e.g. device="001" or device="00[1-2]") as seen in /proc/bus/usb/devices or lsusb(8); including leading zeroes. Note that device numbers are not guaranteed by the OS to be stable across re-boots or device re-plugging.

usb_set_altinterface = bAlternateSetting

Force redundant call to usb_set_altinterface(), especially if needed for devices serving multiple USB roles where the UPS is not represented by the interface number 0 (default).


Set the timer before the UPS is turned off after the kill power command is sent (via the -k switch).

The default value is 20 (in seconds). Usually this must be lower than ondelay, but the driver will not warn you upon startup if it isn’t.

Note that many Cyber Power Systems (CPS) models tend to divide this delay by 60 and round down, so the minimum advisable value is 60 to avoid powering off immediately after NUT sends the shutdown command to the UPS.


Set the timer for the UPS to switch on in case the power returns after the kill power command had been sent, but before the actual switch off. This ensures the machines connected to the UPS are, in all cases, rebooted after a power failure.

The default value is 30 (in seconds). Usually this must be greater than offdelay, but the driver will not warn you upon startup if it isn’t. Some UPSes will restart no matter what, even if the power is (still) out at the moment this timer elapses. In that case, you could see whether setting ondelay = -1 in ups.conf helps.

Note that many CPS models tend to divide this delay by 60 and round down, so the minimum advisable value is 120 to allow a short delay between when the UPS shuts down, and when the power returns.


Set polling frequency for full updates, in seconds. Compared to the quick updates performed every "pollinterval" (the latter option is described in ups.conf(5)), the "pollfreq" interval is for polling the less-critical variables. The default value is 30 (in seconds).


If this flag is set, the driver will not use Interrupt In transfers during the shorter "pollinterval" cycles (not recommended, but needed if these reports are broken on your UPS).


If this flag is set, the driver will treat OL+DISCHRG status as offline. For most devices this combination means calibration or similar maintenance; however some UPS models (e.g. CyberPower UT series) emit OL+DISCHRG when wall power is lost — and need this option to handle shutdowns.


Set to disable fix-ups for broken USB encoding, etc. which we apply by default on certain models (vendors/products) which were reported as not following the protocol strictly. This flag allows to disable the feature in particular device configurations.

It is always possible that the vendors eventually release fixed firmware, or re-use identifiers by which we match suspected broken devices for unrelated products, so processing these fix-ups would be a waste of time there.

It is also always possible that NUT fix-ups cause issues on some devices, whether due to NUT bugs or because the vendor protocol implementation is broken in more than one place.


With this option, the driver will connect to any device, including ones that are not yet supported. This must always be combined with the "vendorid" option. In this mode, the driver will not do anything useful except for printing debugging information (typically used with -DD).


With this option, the driver activates a tweak to workaround buggy firmware returning invalid HID report length. Some APC Back-UPS units are known to have this bug.


If this flag is set, the driver will not poll UPS. This also implies using of INPUT flagged objects. Some Powercom units need this option.


Limit the number of bytes to read from interrupt pipe. For some Powercom units this option should be equal to 8.


The driver automatically tries to reconnect to the UPS on unexpected error. This parameter (in seconds) allows it to wait before attempting the reconnection. The default value is 0.

for instance, it was found that Eaton MGE Ellipse Max 1500 FR UPS firmware stops responding every few hours, which causes usbhid-ups driver to detect an libusb insufficient memory error; in this case, when the usbhid-ups driver tries to reconnect too early, the activity sometimes led the UPS firmware to crash and turn off the load immediately! Setting this parameter to 30 seconds solved this problem (while 20 seconds were not enough).


This driver is not built by default. You can build it by using "configure --with-usb=yes". Note that it will also install other USB drivers.

You also need to install manually the legacy hotplug files (libhidups and libhid.usermap, generally in /etc/hotplug/usb/), or the udev file (nut-usbups.rules, generally in /etc/udev/rules.d/) to address the permission settings problem. For more information, refer to the README file in nut/scripts/hotplug or nut/scripts/udev.


Selecting a specific UPS

As mentioned above, the driver ignores the "port" value in ups.conf. Unlike previous versions of this driver, it is now possible to control multiple UPS units simultaneously with this driver, provided they can be distinguished by setting some combination of the device-matching options. For instance:

        driver = usbhid-ups
        port = auto
        vendorid = 0463
        driver = usbhid-ups
        port = auto
        vendorid = 09ae

USB Polling and Interrupt Transfers

The usbhid-ups driver has two polling intervals. The "pollinterval" configuration option controls what can be considered the "inner loop", where the driver polls and waits briefly for "interrupt" reports. The "pollfreq" option is for less frequent updates of a larger set of values, and as such, we recommend setting that interval to several times the value of "pollinterval".

Many UPSes will respond to a USB Interrupt In transfer with HID reports corresponding to values which have changed. This saves the driver from having to poll each value individually with USB Control transfers. Since the OB and LB status flags are important for a clean shutdown, the driver also explicitly polls the HID paths corresponding to those status bits during the inner "pollinterval" time period. The "pollonly" option can be used to skip the Interrupt In transfers if they are known not to work.


Repetitive timeout and staleness

Some models tends to be unresponsive with the default polling frequency. The result is that your system log will have lots of messages like:

usb 2-1: control timeout on ep0in
usb 2-1: usbfs: USBDEVFS_CONTROL failed cmd usbhid-ups rqt 128 rq 6 len 256
ret -110

In this case, simply modify the general parameter "pollinterval" to a higher value (such as 10 seconds). This should solve the issue.

Note that if you increase "pollinterval" beyond 10 or 15 seconds, you might also want to increase "pollfreq" by the same factor.

Got EPERM: Operation not permitted upon driver startup

You have forgotten to install the hotplug files, as explained in the INSTALLATION section above. Don’t forget to restart hotplug so that it applies these changes.

Unattended shutdowns

The hardware which was used for development of this driver is almost certainly different from what you have, and not all manufacturers follow the USB HID Power Device Class specifications to the letter. You don’t want to find out that yours has issues here when a power failure hits your server room and you’re not around to manually restart your servers.

If you rely on the UPS to shutdown your systems in case of mains failure and to restart them when the power returns, you must test this. You can do so by running upsmon -c fsd. With the mains present, this should bring your systems down and then cycle the power to restart them again. If you do the same without mains present, it should do the same, but in this case, the outputs shall remain off until mains power is applied again.

UPS cuts power too soon

Note that many Cyber Power Systems (CPS) models tend to divide offdelay by 60 and round down, so the minimum advisable value is 60 (seconds) to avoid powering off immediately after NUT sends the shutdown command to the UPS.

UPS does not set battery.charge.low but says OK

Note that many Cyber Power Systems (CPS) models tend to allow only certain values for battery.charge.low and anything outside of the set of allowed values are rounded or ignored.

A shell loop like this can help you map out the allowed values:

for i in `seq 90 -1 0`; do echo "set to $i"; \
    upsrw -s battery.charge.low=$i -u * -p * cps-big; \
    sleep 1; upsc cps-big battery.charge.low; echo ""; \

For example, for CPS PR1000LCDRTXL2U model, the only allowed values are [60,55,50,45,40,35,30,25,20] and in some cases, your UPS may effectively not support a value of 10 for the battery.charge.low setting.


This driver, formerly called newhidups, replaces the legacy hidups driver, which only supported Linux systems.


Originally sponsored by MGE UPS SYSTEMS.

Now sponsored by Eaton

  • Arnaud Quette

  • Peter Selinger

  • Arjen de Korte


The core driver

Internet resources

The NUT (Network UPS Tools) home page: