phase_fault_detection.md

phase_fault_detection

Description

Specifies how to detect and log redundant phase faults in a voltage regulator.

A voltage regulator is sometimes called a "phase controller" because it controls one or more phases that perform the actual voltage regulation.

A regulator may have redundant phases. If a redundant phase fails, the regulator will continue to provide the desired output voltage. However, a phase fault error should be logged warning the user that the regulator has lost redundancy.

The technique used to detect a phase fault varies depending on the regulator hardware. Often a bit is checked in a status register. The status register could exist in the regulator or in a related I/O expander.

Phase fault detection is performed every 15 seconds. A phase fault must be detected two consecutive times (15 seconds apart) before an error is logged. This provides "de-glitching" to ignore transient hardware problems.

Phase faults are detected and logged by executing actions:

• Use the if action to implement the high level behavior "if a fault is detected, then log an error".
• Detecting the fault
  • Use a comparison action like i2c_compare_bit to detect the fault. For example, you may need to check a bit in a status register.
• Logging the error
  • Use the i2c_capture_bytes action to capture additional data about the fault if necessary.
  • Use the log_phase_fault action to log a phase fault error. The error log will include any data previously captured using i2c_capture_bytes.

The actions can be specified in two ways:

• Use the "rule_id" property to specify a standard rule to run.
• Use the "actions" property to specify an array of actions that are unique to this regulator.

The default device for the actions is the voltage regulator. You can specify a different device using the "device_id" property. If you need to access multiple devices, use the set_device action.

Properties

Name	Required	Type	Description
comments	no	array of strings	One or more comment lines describing the phase fault detection.
device_id	no	string	Unique ID of the device to access. If not specified, the default device is the voltage regulator.
rule_id	see notes	string	Unique ID of the rule to execute.
actions	see notes	array of actions	One or more actions to execute.

Notes

• You must specify either "rule_id" or "actions".

Examples

{
  "comments": ["Detect phase fault using I/O expander"],
  "device_id": "io_expander",
  "rule_id": "detect_phase_fault_rule"
}

{
  "comments": [
    "Detect N phase fault using I/O expander.",
    "A fault occurred if bit 3 is ON in register 0x02.",
    "Capture value of registers 0x02 and 0x04 in error log."
  ],
  "device_id": "io_expander",
  "actions": [
    {
      "if": {
        "condition": {
          "i2c_compare_bit": { "register": "0x02", "position": 3, "value": 1 }
        },
        "then": [
          { "i2c_capture_bytes": { "register": "0x02", "count": 1 } },
          { "i2c_capture_bytes": { "register": "0x04", "count": 1 } },
          { "log_phase_fault": { "type": "n" } }
        ]
      }
    }
  ]
}