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Use second QEP, build own custom hardware (PCB)

ThomasV
Intellectual 640 points

Other Parts Discussed in Thread: MOTORWARE

Dear all,

I am using a DRV8301 inverter board with a F28069M Piccolo MCU. If I want to add a second encoder to my system, can this be done directly by connecting it to J10 ('Hall interface')? I doubt this, because in the datasheet of the F2806xM microcontrollers, the GPIOs connected to J10 don't mention eQEP, opposed to the GPIOs from J4 ('Encoder'). Looking at this datasheet, it would be possible to connect a QEP to GPIOs 54-55-56, but these are not used on the DRV8301 board.

I am going to build a custom PCB to make available some unused GPIOs and ADCs anyway, so this can be done, but it would be a lot easier to be able to connect the second encoder directly to the DRV8301 board.

Second thing I am wondering about, would it be possible to control a second motor with this board? Because there are 8 PWM units, and only 3 are used to control one motor.

Third: I see that IA-FB, IB-FB and IC-FB are assigned to two ADC channels each. In what way is this necessary? Is it possible to bring out three of these channels with my custom hardware, in order to read the outputs of extra sensors I want to add?

Lastly, I need two input voltages of 5V and three of 3.3V for the sensors. Is it possible to get these from anywhere from the board?

Thanks in advance.

  • 0
    TI__Guru** 119680 points

    ThomasV said:
    If I want to add a second encoder to my system, can this be done directly by connecting it to J10 ('Hall interface')?

    No.

    ThomasV said:
    I am going to build a custom PCB to make available some unused GPIOs and ADCs anyway, so this can be done, but it would be a lot easier to be able to connect the second encoder directly to the DRV8301 board.

    Not possible.  We have a new Launchpad that will have the 69M and both encoders brought out. Available in January.

    ThomasV said:
    Second thing I am wondering about, would it be possible to control a second motor with this board? Because there are 8 PWM units, and only 3 are used to control one motor.

    From a peripheral / pin perspective yes, the 69M device has enough feedback to control two motors. However, we have not released a software project that shows how to do this in the MotorWare framework. It is possible, and we have products in the market that are doing this....but we have not wrapped up an example into MotorWare, mostly because we didn't have a kit to support the example. This new Launchpad will allow us to show this, but it will take some time before we release the software example. It won't be shown in January.

    If you aren't using InstaSPIN you can make this work pretty quickly.  We have a very old kit that shows two sensorless FOC control loops on F28035 - TMDS2MTRPFCKIT. In fact, some of the third party companies who use graphical development tools already have the new 69M Launchpad and were able to rapidly show operation of two motors under control using their own software blocks....but the InstaSPIN / MotorWare portion will take more time for us.

    ThomasV said:
    Third: I see that IA-FB, IB-FB and IC-FB are assigned to two ADC channels each. In what way is this necessary? Is it possible to bring out three of these channels with my custom hardware, in order to read the outputs of extra sensors I want to add?

    We did this for flexibility on the EVM so it would be possible to sample two pairs of currents at the same instant by using multiple ADC channels. A-B, A-C, B-C. Practically almost no one does this though and so in InstaSPIN solutions we just sample sequentially and we use some logic to decide which samples to ignore if we are in a high modulation area.

    ThomasV said:
    Lastly, I need two input voltages of 5V and three of 3.3V for the sensors. Is it possible to get these from anywhere from the board?

    I honestly don't recall....I think there should be 5V available at the Hall or QEP translators though...