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blazer_usb - Man Page

Driver for Megatec/Q1 protocol USB based UPS equipment


blazer_usb -h

blazer_usb -a UPS_NAME [OPTIONS]


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


Please note that this driver is deprecated and will not receive new development. If it works for managing your devices — fine, but if you are running it to try setting up a new device, please consider the newer nutdrv_qx(8) instead, which should handle all Q* protocol variants for NUT.

Please do also report if your device works with this driver, but nutdrv_qx(8) would not actually support it with any subdriver!

Supported Hardware

The blazer driver is known to work with various UPSes from Blazer, Energy Sistem, Fenton Technologies, General Electric, Mustek and many others. The NUT compatibility table lists all the known supported models. Keep in mind, however, that other models not listed there may also be supported, but haven’t been tested.

All devices with a serial interface (use the blazer_ser driver) and many with a USB interface (use the blazer_usb driver) are supported.

Extra Arguments

You may need to override or provide defaults for some values, depending on the make and model of your UPS. The following are the ones that most likely will need changing (see ups.conf(5)):

default.battery.voltage.high = value

Maximum battery voltage that is reached after about 12 to 24 hours charging. If you want the driver to report a guesstimated battery.charge, you need to specify this (see Battery Charge Guesstimation).

default.battery.voltage.low = value

Minimum battery voltage just before the UPS automatically shuts down. If you want the driver to report a guesstimated battery.charge, you need to specify this (see Battery Charge Guesstimation).

default.battery.voltage.nominal = value, override.battery.voltage.nominal = value

Some devices show a wrong nominal battery voltage (or none at all), so you may need to override or set a default value.

override.battery.packs = value

Some devices report a part of the total battery voltage. For instance, if battery.voltage.nominal is 24 V, but it reports a battery.voltage of around 2 V, the number of battery.packs to correct this reading would be 12. The driver will attempt to detect this automatically, but if this fails somehow, you may want to override this value.

ondelay = value

Time to wait before switching on the UPS (minutes). Note that a value below 3 minutes, may cause earlier firmware versions to not switch on automatically, so it defaults to 3 minutes. The acceptable range is 0..9999 minutes.

offdelay = value

Time to wait before shutting down the UPS (seconds). This value is truncated to units of 6 seconds (less than 60 seconds) or 60 seconds (more than 60 seconds). Defaults to 30 seconds. The acceptable range is 12..600 seconds.


Some UPSes will lock up if you attempt to read rating information from them. Setting this flag will make the driver skip this step.


Some UPSes will lock up if you attempt to read vendor information from them. Setting this flag will make the driver skip this step.

protocol = string

Skip autodetection of the protocol to use and only use the one specified. Supported values megatec, megatec/old, mustek and zinto.

runtimecal = value,value,value,value

Parameter used in the (optional) runtime estimation. This takes two runtimes at different loads. Typically, this uses the runtime at full load and the runtime at half load. For instance, if your UPS has a rated runtime of 240 seconds at full load and 720 seconds at half load, you would enter

runtimecal = 240,100,720,50

The first load should always be higher than the second. If you have values available for loads other than 100 and 50 % respectively, you can use those too, but keep them spaced apart as far as reasonably possible. Just don’t get too close to no load (prediction of runtime depends more on idle load for the battery then).

chargetime = value

The time needed to fully recharge the battery after being fully discharged. If not specified, the driver defaults to 43200 seconds (12 hours). Only used if runtimecal is also specified.

idleload = value

Minimum battery load used by the driver to estimate the runtime. If not specified, the driver defaults to 10%. Only used if runtimecal is also specified.

USB Interface Only

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 syntactically some port configuration must still be there.

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. For devices or operating systems that do not provide sufficient information, the allow_duplicates option can be of use (limited and risky!)

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 on Linux in /sys/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 on Linux in /sys/bus/usb/devices or lsusb(8); including leading zeroes.

device numbers are not guaranteed by the OS to be stable across re-boots or device re-plugging.

busport = regex

If supported by the hardware, OS and libusb on the particular deployment, this option should allow to specify physical port numbers on an USB hub, rather than logical device enumeration values, and in turn — this should be less volatile across reboots or re-plugging. The value may be seen in the USB topology output of lsusb -tv on systems with that tool, for example.

this option is not practically supported by some NUT builds (it should be ignored with a warning then), and not by all systems that NUT can run on.


If you have several UPS devices which may not be uniquely identified by the options above (e.g. only VID:PID can be discovered there), this flag allows each driver instance where it is set to take the first match if available, or proceed to try another.

Normally the driver initialization would abort at this point claiming "Resource busy" or similar error, assuming that the otherwise properly matched device is unique — and some other process already handles it.

This feature is inherently non-deterministic! The association of driver instance name to actual device may vary between runs!

If you only care to know that at least one of your no-name UPSes is online, this option can help.

If you must really know which one, it will not!

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).

usb_config_index, usb_hid_rep_index, usb_hid_desc_index, usb_hid_ep_in, usb_hid_ep_out

Force use of specific interface, endpoint, descriptor index etc. numbers, rather than defaulting to 0 (rarely other values in certain drivers for some devices known to use non-zero numbers). Specified as a hexadecimal number.

As a rule of thumb for usb_hid_desc_index discovery, you can see larger wDescriptorLength values (roughly 600+ bytes) in reports of lsusb or similar tools.

subdriver = string

Select a serial-over-USB subdriver to use. You have a choice between phoenix, ippon, cypress, and krauler. When using this option, it is mandatory to also specify the vendorid and productid.

langid_fix = value

Apply the language ID workaround to the krauler subdriver. This is mandatory for some devices to work (LDLC, Dynamix and others). You must to provide value (0x409 or 0x4095), according to your device entry in NUT hardware compatibility list (HCL).

Ups Commands

This driver supports some instant commands (see upscmd(8)):


Toggle the UPS beeper. (Not available on some hardware.)


Turn on the load immediately.


Turn off the load immediately (see Known Problems).


Turn off the load and return when power is back. Uses the timers defined by ondelay and offdelay.


Turn off the load and remain off (see Known Problems). Uses the timer defined by offdelay.


Stop a shutdown in progress.


Perform a long battery test (Not available on some hardware.)


Perform a (10 second) battery test.

test.battery.start value

Perform a battery test for the duration of value minutes.


Stop a running battery test (not available on some hardware.)

Battery Charge Guesstimation

Due to popular demand, this driver will report a guesstimated battery.charge value and optionally battery.runtime, provided you specified a couple of the Extra Arguments listed above.

If you specify both battery.voltage.high and battery.voltage.low in ups.conf(5), but don’t enter runtimecal, it will guesstimate the state of charge by looking at the battery voltage alone. This is not reliable under load, as this only gives reasonably accurate readings if you disconnect the load, let the battery rest for a couple of minutes and then measure the open cell voltage. This just isn’t practical if the power went out and the UPS is providing power for your systems.

                     battery.voltage - battery.voltage.low
battery.charge =  ------------------------------------------ x 100 %
                  battery.voltage.high - battery.voltage.low

There is a way to get better readings without disconnecting the load, but this requires one to keep track on how much (and how fast) current is going in- and out of the battery. If you specified the runtimecal, the driver will attempt to do this. Note however, that this heavily relies on the values you enter and that the UPS must be able to report the load as well. There are quite a couple of devices that report 0% (or any other fixed value) at all times, in which case this obviously doesn’t work.

The driver also has no way of determining the degradation of the battery capacity over time, so you’ll have to deal with this yourself (by adjusting the values in runtimecal). Also note that the driver guesses the initial state of charge based on the battery voltage, so this may be less than 100%, even when you are certain that they are full. There is just no way to reliably measure this between 0 and 100% full charge.

This is better than nothing (but not by much). If any of the above calculations are giving you incorrect readings, remember that you are the one who put in the values in ups.conf(5), so don’t complain to the author. If you need something better, consider buy an UPS that reports battery.charge and battery.runtime all by itself without the help of a NUT driver.

Notes for the Previous User of Megatec Drivers

The blazer drivers having replaced the megatec ones, some configuration changes may be required by users switching to blazer.

Part of this, the following megatec options, in ups.conf, have to be changed:


You need to use default.battery.voltage.high and default.battery.voltage.low

dtr and rts

You need to use cablepower


This parameter can simply be discarded, since it was a wrong understanding of the specification.

Known Problems

Some UPS commands aren’t supported by all models. In most cases, the driver will send a message to the system log when the user tries to execute an unsupported command. Unfortunately, some models don’t even provide a way for the driver to check for this, so the unsupported commands will silently fail.

Both the load.off and shutdown.stayoff instant commands are meant to turn the load off indefinitely. However, some UPS models don’t allow this.

Some models report a bogus value for the beeper status (will always be enabled or disabled). So, the beeper.toggle command may appear to have no effect in the status reported by the driver when, in fact, it is working fine.

The temperature and load value is known to be bogus in some models.


See Also

blazer_ser(8), nutupsdrv(8), upsc(8), upscmd(8), upsrw(8)

Internet Resources

Referenced By

belkin(8), belkinunv(8), blazer_ser(8), nutdrv_qx(8), nutupsdrv(8), riello_ser(8), riello_usb(8), upsd(8).

07/03/2024 Network UPS Tools 2.8.2. NUT Manual