Your company here — click to reach over 10,000 unique daily visitors

socomec_jbus - Man Page

Driver for Socomec JBUS UPS with RS-232 serial Modbus connection.


socomec_jbus -h

socomec_jbus -a DEVICE_NAME [OPTIONS]


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

Supported Hardware

This driver supports Socomec JBUS series, online (double conversion) UPS with the following characteristics.

  1. Single phase and 3-phase UPS
  2. Connection: RS-232

These are typically provided with a Netvision WEB/SNMP management card / external box that would be better served by the snmp-ups(8) driver. In case netvision isn’t available, you can hook up the UPS directly via the serial port and use this driver.

Currently, it has only been tested on the following model.

In theory, any Socomec JBUS model should work. It should be discovered as “Unknown Socomec JBUS” with a numeric id that I’ll need to add it to the list of supported UPSs.

Sadly, Socomec document only mentions DELPHYS MX and DELPHYS MX elite and I have the id of my own DIGYS, so chances are, your model will not be recognized but will probably mostly work. Please report successful or unsuccessful results to the bug tracker or the mailing list. Make sure to include the full model number of your UPS manually in your report.

socomec_jbus uses the libmodbus project, for Modbus implementation.


The UPS has an RS-232 port which should be connected with a NULL-modem cable to a PC serial port. The UPS tested has a female DB9 connector, so if you construct the cable yourself, make note of the connector type to avoid using gender changers.

RS-232 is supported on all operating systems, either via a built-in serial port on your computer, or by using an external USB-to-RS-232 converter. If you plan to use an USB-to-RS-232 converter, make sure it’s supported by your operating system.


This driver should be built by default if libmodbus and development headers are available. You can force the configure script to build it with the following arguments:

configure --with-serial=yes --with-modbus=yes

You also need to give proper (R/W) permissions on the local serial device file to allow the NUT driver run-time user to access it. This may need additional setup for start-up scripting, udev or upower rules, to apply the rights on every boot — especially if your device nodes are tracked by a virtual filesystem.

For example, a USB-to-serial converter can be identified as /dev/ttyACM0 or /dev/ttyUSB0 on Linux, or /dev/ttyU0 on FreeBSD (note the capital "U"). A built-in serial port can be identified as /dev/ttyS0 on Linux or one of /dev/cua* names on FreeBSD.

Instant Commands

This driver does not (yet?) support sending commands to the UPS.


This driver does not support writable runtime variables (see upsrw(8)): for the same reasons. Both should be trivial to implement, but since I’ve already found one or two inconsistencies in the documentation, I’m withholding from trying them.

Known Issues and Bugs

Well, it is an alpha release at best, but so far appears to report the UPS status reliably. Mostly based on the work of Yifeng Li <tomli@tomli.me> on the huawei-ups2000 in that very same source tree.

Read failure on some JBUS addresses

The driver polls all documented JBUS addresses and it is quite possible that your UPS model does not support one of them (e.g. the Digys does not support address 0x1020 which should provide the current UPS status). This should be logged with LOG_ERR from modbus_read_input_registers() along with the address that produced the error.

Data stale

Under certain circumstances, some registers can return invalid values and trigger a "data stale" error. Once a data stale error has occurred, you should see error messages similar to the example below in the system log.

socomec_jbus: modbus_read_input_registers(addr:XXXX, count:Z):
    Illegal data address
upsd: Data for UPS [socomec] is stale - check driver
upsd: UPS [socomec] data is no longer stale

So far all known problems have been fixed by the author, but an unknown one cannot be ruled out. If you have encountered "data stale" problems during normal uses, please file a bug report with full logs attached.

Before troubleshooting or reporting a problem, it’s important to check your dmesg log for USB connect and disconnect events to avoid wasting time on the NUT driver when the actual problem is USB. For example, if someone yanks the cable out of the USB port, or if a new USB device is plugged into a USB host/hub that is struggling to power its ports (common on single-board computers like Raspberry Pi), or if you have flaky cabling or EMI noise, the serial converter can get disconnected from USB, at least briefly. This creates a permanent data stale, the driver must be restarted (plugging the USB back won’t fix it, since the driver is still using the nonexistent serial device). These USB problems usually have nothing to do with NUT. If it’s the case, you should solve the underlying USB problem - check the cable, check the converter, try a powered USB hub, try a full-speed USB isolator, etc.


Thanos Chatziathanassiou <tchatzi@arx.net>

See Also

The core driver


Internet resources

Referenced By

nutupsdrv(8), upsd(8).

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