A. Example PLDM Command and Response Messages
This section provides an example command to read the board temperatures through PLDM over MCTP SMBus.
Use the following commands to read the board temperatures:
- GetPDR
- GetSensorReading
GetPDR
Run the GetPDR command with the board temperature PDR record handle (13) to get the board sensor ID, and temperature conversion formula. You can also observe threshold values set for the board temperature sensor.
GetPDR Request Command (0x51):
The length of the write data is 25.
Below is the representation of the GetPDR command arranged in their respective SMBUS, MCTP, PLDM header location.
Figure 4. GetPDR Command Packet Fields
To decode the PLDM message payload, refer to DSP0248_1.2.0 spec.
| GetPDR Request Data | Value |
|---|---|
| recordHandle | 0x0000_000D – PDR handle for board temperature is 13 |
| dataTransferHandle | 0x0000_0000 |
| transferOperationFlag | 0x01 |
| requestCount | 0x0080 (128 bytes) |
| recordChangeNumber | 0x0000 |
GetPDR Response:
The length of the received data is 131 bytes.
Below is the presentation of the of the above command arranged in their respective SMBUS, MCTP, PLDM header location
Figure 5. GetPDR Response Message Packet Fields
PLDM response message payload for GetPDR:
To decode the PLDM message payload, refer to DSP0248_1.2.0 specification:
| GetPDRResponse Data | Value |
|---|---|
| Completion code | 0x00 |
| nextRecordHandle | 0x0000_0002 |
| nextDataTransferHandle | 0x0000_0000 |
| transferFlag | 0x05 |
| responseCount | 0x0069 = 105 bytes |
| recordData | 0x00 |
| Common PDR Header Format | Value |
|---|---|
| recordHandle | 0x0000_0001 |
| PDRHeaderVersion | 0x01 |
| PDRType | 0x02 |
| recordChangeNumber | 0x0000 |
| dataLength | 0x005F = 95 bytes |
| Numeric Sensor PDR Format | Value |
|---|---|
| PLDMTerminusHandle | 0x1234 |
| sensorID | 0x0001 |
| entityType | 0x003E |
| entityInstanceNumber | 0x0001 |
| containerID | 0x0123 |
| sensorInit | 0x00- noInit |
| sensorAuxiliaryNamesPDR | 0x01 - False |
| baseUnit | 0x02 - units -Degrees C |
| unitModifier | 0x00 |
| rateUnit | 0x00 |
| baseOEMUnitHandle | 0x00 |
| auxUnit | 0x00 |
| auxUnitModifier | 0x00 |
| auxrateUnit | 0x00 |
| rel | 0x00 |
| auxOEMUnitHandle | 0x00 |
| isLinear | 0x01 |
| sensorDataSize | 0x05 -Sint32 |
| resolution | 0x3F00_0000 (IEEE754 conversion is 0.5) |
| offset | 0x00 (IEEE 754 conversion is 0.0) |
| accuracy | 0x00 |
| plusTolerance | 0x02 |
| minusTolerance | 0x02 |
| hysteresis | 0x0000_0014 |
| supportedThresholds | 0x05 |
| thresholdAndHysteresisVolatility | 0x06 |
| stateTransitionInterval | 0x4040_0000 (IEEE 754 conversion is 3.0) |
| updateInterval | 0x4040_0000 (IEEE 754 conversion is 3.0) |
| maxReadable | 0x0000_00FE |
| minReadable | 0x0000_0000 |
| rangeFieldFormat | 0x05 - Sint32 |
| rangeFieldSupport | 0x0010_0000 |
| nominalValue | 0x0000_0000 |
| normalMax | 0x0000_0000 |
| normalMin | 0x0000_0000 |
| warningHigh | 0x0000_0055 = 85 units |
| warningLow | 0x0000_0000 |
| criticalHigh | 0x0000_0000 |
| criticalLow | 0x0000_0000 |
| fatalHigh | 0x0000_0064 = 100 units |
| fatalLow | 0x0000_0000 |
| PEC | 0xF2 |
You can observe the following values from the above table:
- The sensor ID for board temperature is 0x0001
- Upper Warning high value is 85 °C
- Upper Fatal high value is 100 °C
- The reading conversation formula is Y= (m*X+B) where,
- Y= Converted reading in units
- X= Reading from sensor obtained by running GetSensorReading command
- m= Resolution from PDR in units (0.5)
- B = Offset from PDR in units (0.0)
GetSensorReading
Run the GetSensorReading command to get the raw sensor reading of the board temperature.
GetSensorReading Command (0x11):
the length of the write data is 15.
Below is the of the above command arranged in their respective SMBUS, MCTP, PLDM header location.
Figure 6. GetSensorReading Command Packet Fields
To decode the PLDM message payload, refer to DSP0248_1.2.0 specification.
| GetSensorReading Requestdata | Value |
|---|---|
| sensorID | 0x0001 |
| rearmEventState | 0x00 |
GetSensorReading Response:
The length of the received data is 24.
Figure 7. GetSensorReading Response Message Packet Fields
To decode the PLDM message Payload, refer to DSP0248_1.2.0 specification.
| GetSensorReading Response | Value |
|---|---|
| CompletionCode | 0x00 |
| SensorDataSize | 0x05 - sint32 |
| SensorOperationalState | 0x00 -enabled |
| SensorEventMessageEnable | 0x00 |
| presentState | 0x01 - Normal |
| previousState | 0x00 - unknown |
| eventState | 0x01- Normal |
| presentReading | 0x0000_0045 = 69 units |
You can observe the following values from the above table:
- The raw data value of board temperature is 69 °C
- Find the actual temperature using the conversion formula, Y=(m*X+B)
- Actual Board temperature value = (69*0.5+0.0)= 34.5 °C