Frequently Asked Question

Firmware fix for module not detected issues for ALL SiteMonitor Expansion Modules (Including SyncInjectors) (08-Jan-2015)
Last Updated 5 years ago

We have discovered a bug where certain Revision H expansion modules will not be reliably detected by the SiteMonitor Base Unit.   The attached firmware files fix this bug in all Revision H devices.

This bug is triggered primarily in a situation where the expansion bus is already carrying traffic while the expansion module is booting.  If a module sees data on the expansion bus before it is fully booted, it will often cause the communications hardware used to talk on the expansion bus to lock up.  In the previous version of the firmware, this state was neither detected nor cleared correctly, causing the expansion module to simply cease listening to *any* messages on the bus, until such time as that module is rebooted.

The two most common causes of this issue are as follows:
  • At initial power on, in which case a quickly-booting base unit may send messages before a slower-booting expansion module is ready for them, causing the slow-booting expansion module's communication hardware to lock up.   This will often only present itself with certain combinations of base units and expansion modules, due to the normal variation of bootup speeds from one device to another.
  • During normal operations, when an expansion module reboots for some reason (intermittent cable, esd event, etc) while the expansion bus is busy with traffic for it or for other modules. 
The firmware files provided below will resolve this issue in all revision H and later modules.   Earlier devices appear to be immune from this bug.

To apply this firmware, you will need to follow the instructions at  Unfortunately, the an early step in this procedure is to ensure the modules are detected and active, which can be a challenge with modules which are currently exhibiting this bug.   There are two different procedures we have developed which seem to reliably cause the expansion module to be detected for sufficient time for the upgrade to be performed.  They are described below.

Option 1:  Upgrade Base II unit to latest (currently beta) version. 

The beta base unit firmware available at waits a bit longer at boot time to permit the expansion modules to reboot.  This should greatly improve reliability of detection of modules with this bug in firmware.  We believe this firmware is stable and ready for production use, but we simply do not have enough in-field use to be sure of this, so there is a bit more risk, than option #2 below. 

One caveat:  certain modules have a secondary power source other than the base unit (most notably our SyncInjector products).   These modules will continue to operate through a base unit reboot without themselves rebooting, and as such will not be power cycled and will still not be able to talk on the bus. For these modules, if they are not detected after a reboot, you will still need to remove power from both the base unit and the expansion module simultaneously in order for them to be detected.  Once this has been done they should appear in the list of attached modules. Where the modules share a common power source, removing the common power source (such as unplugging a shared power supply) and reconnecting it should be sufficient to cause a detection - the important factor being that *all* sources of power powering either the base unit or the expansion modules be removed simultaneously.
For this reason, the steps to complete this option are as follows:

1.  Upgrade all expansion modules which are currently listed as available in the expansion module tab, following the instructions at
2.  Upgrade the Base II to the latest beta firmware from
3.  Check for any available and not-upgraded modules in the expansion module tab and upgrade any you find.
4.  If there are any expansion modules which still remain not detected and not upgraded, remove power from both the expansion modules and from the base unit.  Wait a few seconds, and reconnect the power.  This will reset the additional expansion modules, permitting them to be ugpgraded. Upgrade the final expansion modules. 

Option 2:  Prevent base unit from transmitting on the bus while the units are rebooted.

This procedure is a bit more involved:

  1. Upgrade all detected modules with the latest firmware.
  2. Detach all secondary power sources from the expansion modules.  This primarily applies to SyncInjectors, 5 Channel PDU's, and Single Port Gigabit PoE Injectors.   These modules are powered by both the base unit and the power input on the device, and need to have the power removed from the power input on the device itself in order to be rebooted.
  3. In the SiteMonitor Base II web interface, go to the Binary I/O, and set the value for expansion power to '0'.  This will turn off expansion power.   If this is not a Base II, either switch to a Base II temporarily (highly recommended for this procedure) or contact us for a significantly higher risk procedure which may work.
  4. In the SiteMonitor Base II, go into the Expansion Units tab.  Make note of the serial numbers of all devices so you can restore them in order later.
  5. Click on each serial number, and enter '0'.   When you are done, all serial numbers should be listed as '0'.
  6. Click on Rescan.  This should clear out all modules *other* than the base unit, and prevent the base unit from attempting to reach modules on the expansion bus.  If there are *any* modules other than the base unit listed, go back to step 3 and repeat until only the base unit is listed.
  7. Go back to the Binary I/O tab, and set the value for expansion power back to '1'.  This will turn the expansion unit back on.  Wait several seconds for the unit to reboot fully.
  8. Go back into the Expansion Units tab, and click on rescan.   The modules should appear in the list of expansion modules.
  9. Upgrade the detected modules with the latest firmware.
  10. If not all modules are detected, you may want try to  connect only the non-detected module to the Base II and start over at step 3.
  11. Once you have all the modules upgraded, reattach them and their power, and go into the expansion tab.   Enter the serial numbers you recorded in step 4 in order on the screen.   Click on rescan and the devices should reattach in the order you specified.
Firmware Files:

Firmware for 2 Relay 3 Switch Modules (20150108)
Firmware for 2 Shunt 4 Voltmeter Modules (20150108)
Firmware for 3 Shunt 3 Voltmeter Modules (20150108)
Firmware for 6 Voltmeter Modules (20150108)
Firmware for 5 Channel PDU Modules - Obtain the updated file from
Firmware for Single Port Gigabit PoE Injectors (Airfiber, etc) (20150108)
Firmware for Intelligent Temperature Controllers (RevH Only) (20150108)
Firmware for 4 Port PoE Injectors (RevH Only) (20150108)
Firmware for 8 Port PoE Injectors (RevH Only) (20150108)
Firmware for 4 Port Gigabit PoE Injectors (20150108)
Firmware for 8 Port Gigabit PoE Injectors (20150108)
Firmware for 4 Relay Output Modules (RevH Only) (20150108)
Firmware for 6 Switch Input Modules (RevH Only) (20150108)
Firmware for APC Smart UPS Modules (RevH Only) (20150108)
Firmware for SunsaverMPPT (Meterbus) Modules (RevH Only) (20150108)
Firmware for TriStarMPPT (Serial) Modules (RevH Only) (20150108)
Firmware for TriStar (Non-MPPT, Serial) Modules (RevH Only) (20150108)
Firmware for all Revision H, H0 or H1 SyncInjectors - Obtain the updated file from

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