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MCF8329A: How does MotorStudio measure the rotation speed for MCF8329A

Alex Kiselev
Prodigy 20 points
Part Number: MCF8329A
Other Parts Discussed in Thread: MOTORSTUDIO

Tool/software:

Hello, I'm using MCF8329A to control a BLDC motor. Everything works fine so far, but the value for the Speed FDBK in MotorStudio window is about 4 times higher than a real speed value which I observe.

My BLDC Motor has 4 pole pairs (or 8 poles), so I guess the difference is related to this.

I don't find any pole settings in the datasheet except of FG_DIV in CLOSED_LOOP1 register, I tried to configure it there but without any changes of the measured values.

Where does this Speed FDBK value come from? How can i set something up so that it shows the correct value?

  • 0
    TI__Expert 6011 points

    Hi Alex,

    Thanks for reaching out. Could you read the FG_SPEED_FDBK instead, after setting FG_DIV appropriately. 

    Do note that this variable is refreshed much slower compared to SPEED_FDBK.

    Regards,

    Sachin S

  • 0
    TI__Mastermind 23202 points

    Hi Alex,

    Speed FDBK is per unit value, how are you converting? This is signed value.

    FG Feed back provided cycles , you can verify that as well.

    Can you share JSON and RSHUNT value?

    Thanks and Best Regards

    Venkatadri S

  • 0 in reply to Venkatadri Shantaram84961
    Prodigy 20 points

    Hello Venkatadri,

    here is my JSON file, Rshunt is 1mOhm. Actually I don't convert the feedback value, I am working with MotorStudio, the question is how MotorStudio does measure this feedback. I can see, that FG_DIV can be configured for different amount of pole pairs, but does it affect another feedbacks?

    {
"signature":"oneui-register-data",
"data":[
[
{
"idx":0,
"id":"ISD_CONFIG",
"value":"0x65A2D4E1",
"addr":"0x00000080"
},
{
"idx":1,
"id":"REV_DRIVE_CONFIG",
"value":"0x48300000",
"addr":"0x00000082"
},
{
"idx":2,
"id":"MOTOR_STARTUP1",
"value":"0x086650C0",
"addr":"0x00000084"
},
{
"idx":3,
"id":"MOTOR_STARTUP2",
"value":"0x2B81C007",
"addr":"0x00000086"
},
{
"idx":4,
"id":"CLOSED_LOOP1",
"value":"0x157181B8",
"addr":"0x00000088"
},
{
"idx":5,
"id":"CLOSED_LOOP2",
"value":"0x0AAD123A",
"addr":"0x0000008A"
},
{
"idx":6,
"id":"CLOSED_LOOP3",
"value":"0x50800000",
"addr":"0x0000008C"
},
{
"idx":7,
"id":"CLOSED_LOOP4",
"value":"0x485204B0",
"addr":"0x0000008E"
},
{
"idx":8,
"id":"REF_PROFILES1",
"value":"0x00000000",
"addr":"0x00000094"
},
{
"idx":9,
"id":"REF_PROFILES2",
"value":"0x00000000",
"addr":"0x00000096"
},
{
"idx":10,
"id":"REF_PROFILES3",
"value":"0x00000004",
"addr":"0x00000098"
},
{
"idx":11,
"id":"REF_PROFILES4",
"value":"0x00000000",
"addr":"0x0000009A"
},
{
"idx":12,
"id":"REF_PROFILES5",
"value":"0x00000000",
"addr":"0x0000009C"
},
{
"idx":13,
"id":"REF_PROFILES6",
"value":"0x00000000",
"addr":"0x0000009E"
}
],
[
{
"idx":0,
"id":"FAULT_CONFIG1",
"value":"0x465A31A6",
"addr":"0x00000090"
},
{
"idx":1,
"id":"FAULT_CONFIG2",
"value":"0x71422888",
"addr":"0x00000092"
}
],
[
{
"idx":0,
"id":"INT_ALGO_1",
"value":"0x0A86037D",
"addr":"0x000000A0"
},
{
"idx":1,
"id":"INT_ALGO_2",
"value":"0x020082E3",
"addr":"0x000000A2"
}
],
[
{
"idx":0,
"id":"PIN_CONFIG",
"value":"0x40032308",
"addr":"0x000000A4"
},
{
"idx":1,
"id":"DEVICE_CONFIG1",
"value":"0x20100002",
"addr":"0x000000A6"
},
{
"idx":2,
"id":"DEVICE_CONFIG2",
"value":"0x03E8C00C",
"addr":"0x000000A8"
},
{
"idx":3,
"id":"PERI_CONFIG1",
"value":"0x2A9845C0",
"addr":"0x000000AA"
},
{
"idx":4,
"id":"GD_CONFIG1",
"value":"0x0100807B",
"addr":"0x000000AC"
},
{
"idx":5,
"id":"GD_CONFIG2",
"value":"0x00000400",
"addr":"0x000000AE"
}
],
[
{
"idx":0,
"id":"GATE_DRIVER_FAULT_STATUS",
"value":"0x00000000",
"addr":"0x000000E0"
},
{
"idx":1,
"id":"CONTROLLER_FAULT_STATUS",
"value":"0x00000000",
"addr":"0x000000E2"
}
],
[
{
"idx":0,
"id":"ALGO_STATUS",
"value":"0x0B610004",
"addr":"0x000000E4"
},
{
"idx":1,
"id":"MTR_PARAMS",
"value":"0x00000000",
"addr":"0x000000E6"
},
{
"idx":2,
"id":"ALGO_STATUS_MPET",
"value":"0x00000000",
"addr":"0x000000E8"
}
],
[
{
"idx":0,
"id":"ALGO_CTRL1",
"value":"0x20000000",
"addr":"0x000000EA"
}
],
[
{
"idx":0,
"id":"ALGO_DEBUG1",
"value":"0x80000000",
"addr":"0x000000EC"
},
{
"idx":1,
"id":"ALGO_DEBUG2",
"value":"0x00000018",
"addr":"0x000000EE"
},
{
"idx":2,
"id":"CURRENT_PI",
"value":"0x00280236",
"addr":"0x000000F0"
},
{
"idx":3,
"id":"SPEED_PI",
"value":"0x01480048",
"addr":"0x000000F2"
},
{
"idx":4,
"id":"DAC_1",
"value":"0x00000000",
"addr":"0x000000F4"
}
],
[
{
"idx":0,
"id":"ALGORITHM_STATE",
"value":"0x00000000",
"addr":"0x00000196"
},
{
"idx":1,
"id":"FG_SPEED_FDBK",
"value":"0x00BEE3B6",
"addr":"0x0000019C"
},
{
"idx":2,
"id":"BUS_CURRENT",
"value":"0x00000000",
"addr":"0x0000040E"
},
{
"idx":3,
"id":"PHASE_CURRENT_A",
"value":"0xFFFC0000",
"addr":"0x0000043C"
},
{
"idx":4,
"id":"PHASE_CURRENT_B",
"value":"0x00080000",
"addr":"0x0000043E"
},
{
"idx":5,
"id":"PHASE_CURRENT_C",
"value":"0xFFFC0000",
"addr":"0x00000440"
},
{
"idx":6,
"id":"CSA_GAIN_FEEDBACK",
"value":"0x00000000",
"addr":"0x00000450"
},
{
"idx":7,
"id":"VOLTAGE_GAIN_FEEDBACK",
"value":"0x00000000",
"addr":"0x00000458"
},
{
"idx":8,
"id":"VM_VOLTAGE",
"value":"0x040B0000",
"addr":"0x0000045C"
},
{
"idx":9,
"id":"PHASE_VOLTAGE_VA",
"value":"0x02D93181",
"addr":"0x00000460"
},
{
"idx":10,
"id":"PHASE_VOLTAGE_VB",
"value":"0x02D93181",
"addr":"0x00000462"
},
{
"idx":11,
"id":"PHASE_VOLTAGE_VC",
"value":"0x02DCA850",
"addr":"0x00000464"
},
{
"idx":12,
"id":"SIN_COMMUTATION_ANGLE",
"value":"0x06AD19F0",
"addr":"0x000004AA"
},
{
"idx":13,
"id":"COS_COMMUTATION_ANGLE",
"value":"0x04635970",
"addr":"0x000004AC"
},
{
"idx":14,
"id":"IALPHA",
"value":"0xFFD10000",
"addr":"0x000004CC"
},
{
"idx":15,
"id":"IBETA",
"value":"0x000AF83B",
"addr":"0x000004CE"
},
{
"idx":16,
"id":"VALPHA",
"value":"0xFFB79D69",
"addr":"0x000004D0"
},
{
"idx":17,
"id":"VBETA",
"value":"0x00393012",
"addr":"0x000004D2"
},
{
"idx":18,
"id":"ID",
"value":"0xFFEE7B0D",
"addr":"0x000004DC"
},
{
"idx":19,
"id":"IQ",
"value":"0x002CEAAA",
"addr":"0x000004DE"
},
{
"idx":20,
"id":"VD",
"value":"0x00080AD3",
"addr":"0x000004E0"
},
{
"idx":21,
"id":"VQ",
"value":"0x005C063E",
"addr":"0x000004E2"
},
{
"idx":22,
"id":"IQ_REF_ROTOR_ALIGN",
"value":"0x00000000",
"addr":"0x0000051A"
},
{
"idx":23,
"id":"SPEED_REF_OPEN_LOOP",
"value":"0x00000000",
"addr":"0x00000532"
},
{
"idx":24,
"id":"IQ_REF_OPEN_LOOP",
"value":"0x02665D58",
"addr":"0x00000542"
},
{
"idx":25,
"id":"SPEED_REF_CLOSED_LOOP",
"value":"0x00000000",
"addr":"0x000005D0"
},
{
"idx":26,
"id":"ID_REF_CLOSED_LOOP",
"value":"0x00000000",
"addr":"0x0000060A"
},
{
"idx":27,
"id":"IQ_REF_CLOSED_LOOP",
"value":"0x00000000",
"addr":"0x0000060C"
},
{
"idx":28,
"id":"ISD_STATE",
"value":"0x00000005",
"addr":"0x000006B0"
},
{
"idx":29,
"id":"ISD_SPEED",
"value":"0x00000295",
"addr":"0x000006BA"
},
{
"idx":30,
"id":"IPD_STATE",
"value":"0x00000000",
"addr":"0x000006E4"
},
{
"idx":31,
"id":"IPD_ANGLE",
"value":"0x00000000",
"addr":"0x0000071A"
},
{
"idx":32,
"id":"ED",
"value":"0x00000000",
"addr":"0x0000075C"
},
{
"idx":33,
"id":"EQ",
"value":"0x00000000",
"addr":"0x0000075E"
},
{
"idx":34,
"id":"SPEED_FDBK",
"value":"0x00000000",
"addr":"0x0000076E"
},
{
"idx":35,
"id":"THETA_EST",
"value":"0x00000000",
"addr":"0x00000774"
}
]
]
}

  • 0 in reply to Sachin S
    Prodigy 20 points

    Hello Sachin,

    does it mean that SPEED_FDBK value is reported in MotorStudio as Speed FDBK? Does FG_DIV affect this value then?

  • +1 in reply to Alex Kiselev
    TI__Expert 6011 points

    Hi Alex,

    You are right, SPEED_FDBK is reported as Speed FDBK in MotorStudio. FG_DIV does not affect this value.

    Regards,
    Sachin S

  • 0 in reply to Sachin S
    TI__Expert 6011 points

    Also FG_DIV affects the FG pin output frequency too.

  • 0 in reply to Sachin S
    Prodigy 20 points

    Hello Sachin, thanks for your reply, now I understand what I observe. So if I want to get a right value, I have to divide it in my software and there is no possibility to compensate it internally?

  • 0 in reply to Alex Kiselev
    TI__Expert 6011 points

    Hi Alex,

    For SPEED_FDBK yes, but for FG_SPEED_FDBK you can use the FG_DIV to compensate as I mentioned before

    Alex Kiselev said:
    o if I want to get a right value, I have to divide it in my software and there is no possibility to compensate it internally
  • 0 in reply to Sachin S
    Prodigy 20 points

    Hello Sachin, thank you for the clarification!

  • 0 in reply to Alex Kiselev
    TI__Expert 6011 points

    Alex, I was referring to the MOTORSTUDIO charts. The actual value of FG_SPEED_FDBK does not change. Apologies for the wrong information previously. 

    Sachin S said:

    Thanks for reaching out. Could you read the FG_SPEED_FDBK instead, after setting FG_DIV appropriately. 

    Do note that this variable is refreshed much slower compared to SPEED_FDBK.