USB HID Compliance - SMT750C

[kevinwc]

Hello,

I am developing software to communicate with a SMT750C Smart-UPS (firmware ID 1060) using USB HID. Can you confirm that the SMT750C firmware ID 1060 complies with the USB HID details in Application Note 178? The reported usage pages and report IDs from the device do not align with the details in the application note.

Here are the details of the USB HID report descriptor:

Spoiler

American Power Conversion Smart-UPS 750 FW:UPS 02.0 / ID=1060 (VID 1309, PID 4, version 0.1)
Report Descriptor:

05 00 09 01 A1 01 85 89 06 86 FF 09 FD 15 00 25 FF 35 00 45 00 65 00 55 00 75 08 95 3F 81 02 85 90 09 FC 91 02 85 96 09 F1 B1 22 85 8D 09 F7 95 02 B1 22 25 01 45 01 75 01 96 E8 01 B1 03 85 92 09 F4 25 FF 45 00 75 08 95 02 B1 23 25 01 45 01 75 01 96 E8 01 B1 03 85 93 09 F3 25 FF 45 00 75 08 95 02 B1 22 25 01 45 01 75 01 96 E8 01 B1 03 85 94 09 F2 25 FF 45 00 75 08 95 02 B1 23 25 01 45 01 75 01 96 E8 01 B1 03 85 8E 09 F6 25 FF 45 00 75 08 95 04 B1 23 25 01 45 01 75 01 96 D8 01 B1 03 C1 00 (164 bytes)

Interpretation:  
UsagePage 0

  Usage 1

  Collection 1

    ReportID 137

    UsagePage 65414

    Usage 253

    LogicalMinimum 0

    LogicalMaximum 255

    PhysicalMinimum 0

    PhysicalMaximum 0

    Unit 0

    UnitExponent 0

    ReportSize 8

    ReportCount 63

    Input 2

    ReportID 144

    Usage 252

    Output 2

    ReportID 150

    Usage 241

    Feature 34

    ReportID 141

    Usage 247

    ReportCount 2

    Feature 34

    LogicalMaximum 1

    PhysicalMaximum 1

    ReportSize 1

    ReportCount 488

    Feature 3

    ReportID 146

    Usage 244

    LogicalMaximum 255

    PhysicalMaximum 0

    ReportSize 8

    ReportCount 2

    Feature 35

    LogicalMaximum 1

    PhysicalMaximum 1

    ReportSize 1

    ReportCount 488

    Feature 3

    ReportID 147

    Usage 243

    LogicalMaximum 255

    PhysicalMaximum 0

    ReportSize 8

    ReportCount 2

    Feature 34

    LogicalMaximum 1

    PhysicalMaximum 1

    ReportSize 1

    ReportCount 488

    Feature 3

    ReportID 148

    Usage 242

    LogicalMaximum 255

    PhysicalMaximum 0

    ReportSize 8

    ReportCount 2

    Feature 35

    LogicalMaximum 1

    PhysicalMaximum 1

    ReportSize 1

    ReportCount 488

    Feature 3

    ReportID 142

    Usage 246

    LogicalMaximum 255

    PhysicalMaximum 0

    ReportSize 8

    ReportCount 4

    Feature 35

    LogicalMaximum 1

    PhysicalMaximum 1

    ReportSize 1

    ReportCount 472

    Feature 3

  EndCollection 0

If you can share any additional documentation for communicating with this device using USB HID, it would be most appreciated. Thank you for your time.

-Kevin C.

[KarimEissa]

Hello,

USB port on the back of the UPS ,you only Use this port to connect to a computer for monitoring or gracefully shutting down the UPS using
PowerChute software as per the attachment

So we recommends only communicate with the UPS using PCSS software with the supplied USB or serial cables provided with the UPS and we do not encourage to use any third party software tool or any smart signaling cables as they would be a risk for UPS control board corruption and may causes  UPS sudden shutdown or premature  damage to the controller

please refer to PCSS documentation for your references

https://www.se.com/uk/en/product-range/137943580-powerchute-serial-shutdown/#documents

and these are the recommended cables to be used with unit for powerchute signaling are shown below :

940-0504 (USB A to USB A)
940-0625A or 940-1525A (smart signaling serial)
940-0128D (simple signaling serial)

and refer to the below FAQ to install PCSS for UPS monitoring and server shutdown

https://www.se.com/uk/en/faqs/FA338817/

Regards,

Karim

[fredkm · Accepted solution]

That Application Note dates from 2013. I have an old SMT750I where the report descriptor matches the HID elements from the Note. My report descriptor is 1623 bytes, while yours is only 164 bytes and misses most of the usages. So, to me it looks like your newer SMT750C doesn't comply with USB HID details from Application Note.

Probably not surprising as these units use a proprietary protocol for communicating with the UPS. USB HID is only used for device discovery and setup.

[kevinwc]

Hi Fred,

I did eventually receive the expected descriptors and can acquire status information using HID. I wish I knew exactly what changed with my setup between receiving the report descriptor I originally posted and receiving the expected one, but I don't have a clear answer. Could have been something as simple as power cycling everything.

Thanks for looking into it - I appreciate it.