TMS320F280025: AIO as trip zone

Emma Wang

Expert 5290 points

Part Number: TMS320F280025

hi expert，

by the appnote，https://www.ti.com/lit/an/spracp6/spracp6.pdf

we know it is a way to save GPIO by using AIO as trip zone.

And we also give the design method.

But it is not really clear.

Now customer want to use it on F280025.

Here are two questions:

1.how high dv/dt is the upper limit?

2.what value of the series resistor do you recommend in the system?

Emma

over 5 years ago

0 Santosh Jha over 5 years ago

TI__Guru 50611 points

Hi Emma,

Due to US holiday, Frank is out of office this week. We will respond by Dec 1st. Sincere apology for inconvenience.

0 Joseph Casuga over 5 years ago in reply to Santosh Jha

TI__Mastermind 40330 points

Hi Emma,

On the F280025 part, we performed an evaluation where ADC is converting a 100KHz sine signal while another AIO is driven with a 3.77KHz square wave. We did not notice any significant degradation on the AC specs (SNR, THD, ENOB). This is probably the same scenario compared to when AIO used as a trip indicator. In our evaluation setup, we used the datasheet recommended supply capacitors. This is important as supply capacitors would also help reduce noise coupling from the input pins to the supply rails.

Regards,

Joseph

0 Emma Wang over 5 years ago in reply to Joseph Casuga

TI__Expert 5290 points

Hi Josepe,

thanks for your reply. It is helpful.

Besides the HW design, I also have a SW question.

In the same document, we give the example code, and it uses TRIP4.

// enable digital mode for AIO243(B5)
GPIO_setAnalogMode(243, GPIO_ANALOG_DISABLED);
GPIO_setPinConfig(GPIO_243_GPIO243);
GPIO_setDirectionMode(243, GPIO_DIR_MODE_IN);
GPIO_setPadConfig(234U, GPIO_PIN_TYPE_STD);
//Configure AIO243 as INPUT X-BAR 1
XBAR_setInputPin(XBAR_INPUT1, 243);
// Configure INPUT X-BAR 1 as EPWM X-BAR TRIP4
XBAR_setEPWMMuxConfig(XBAR_TRIP4, XBAR_EPWM_MUX01_INPUTXBAR1);
XBAR_enableEPWMMux(XBAR_TRIP4, XBAR_MUX01);

My question is, if I want to use TRIP1-3, should I just delete the last two code line, since input x-bar1-3 is connecting to TRIP1-3 by hardware.

//XBAR_setEPWMMuxConfig(XBAR_TRIP4, XBAR_EPWM_MUX01_INPUTXBAR1);
//XBAR_enableEPWMMux(XBAR_TRIP4, XBAR_MUX01);

Emma

0 Jason Whiles over 5 years ago in reply to Emma Wang

TI__Expert 5840 points

Emma,

This is correct, you do not need to configure the EPWM XBAR for TRIP3.

Best regards,

Jason

0 Emma Wang over 5 years ago in reply to Jason Whiles

TI__Expert 5290 points

Jason,

Thanks, I test myself and it did work.

at the begining, I went into an error when connecting debugger.

void __error__(char *filename, uint32_t line)
{
    //
    // An ASSERT condition was evaluated as false. You can use the filename and
    // line parameters to determine what went wrong.
    //
    ESTOP0;
}

I click 'step return' then I found it is located at XBAR_setInputPin function.

XBAR_setInputPin(uint32_t base, XBAR_InputNum input, uint16_t pin)
{
    //
    // Check the argument.
    //
    ASSERT((pin <= XBAR_GPIO_AIO_MAX_CNT) ||
          ((pin >= XBAR_NON_GPIO_MIN_CNT) && (pin <= XBAR_NON_GPIO_MAX_CNT)));
    ASSERT(XBAR_isBaseValid(base));

    //
    // Write the requested pin to the appropriate input select register.
    //
    EALLOW;

    HWREGH(base + XBAR_O_INPUT1SELECT + (uint16_t)input) = pin;

    EDIS;
}

and I found pin should below XBAR_GPIO_MAX_CNT(46U) so I changed to XBAR_GPIO_AIO_MAX_CNT by myself.

Then everything goes right.

Emma

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TMS320F280025: AIO as trip zone