TMS570LS1224: Controlling an N2HET PWM signal

Hi,

I am trying to control a PWM signal generated using the N2HET.

So far I am able to see a PWM signal with a fixed frequency and a duty cycle of 25%, but I don't seem able to control this on-the-fly. I am assuming that my HalCoGen settings are valid in order to see any output at all.

As a basic test (on a LaunchpadXL board) I am programming an ADC to obtain a modifiable value, scaled to 0-100%, and I am trying to feed this into a pwmSetSignal() function to control the duty cycle.

My very simple code is:

    adcData_t adc_data;
    adcData_t *adc_data_ptr = &adc_data;
    unsigned int value;
    unsigned int duty_cycle;
    hetSIGNAL_t het_sig;

    het_sig.duty=50;
    het_sig.period = 1.000;        /* 1us := 1MHz */

    hetInit();
    adcInit();
 
    pwmStart(hetRAM1, pwm0);

    while(1)
    {
        /* Get modifiable value from ADC */
        adcStartConversion(adcREG1, adcGROUP1);
        while(!adcIsConversionComplete(adcREG1, adcGROUP1));
        adcGetData(adcREG1, 1U, adc_data_ptr);
        value = (unsigned int)adc_data_ptr->value;

        /* Relate the value (0-4095) to a percentage (0-100) for the PWM duty cycle */
        /* The value/41 gives the duty cycle percentage, with a maximum of 99 */
        duty_cycle = value / 41;

        /* Update duty cycle with value from ADC */
        het_sig.duty=duty_cycle;
//        pwmSetSignal(hetRAM1, pwm4, het_sig);
    }

When I run this code I call see on a 'scope that there is a 175.7kHz PWM signal with a 25% duty cycle.

My HalCoGen settings for pwm0 are: Period = 0.1, Duty Cycle = 10. What I am seeing bears no relation to the HalCoGen settings.

When I uncomment the call to pwmSetSignal(), the PWM output is killed completely.

My ultimate objective is to produce a PWM signal at the highest possible frequency, but (most importantly) with a controllable duty cycle over the range 0 to 99%.

Questions:

1. Can you advise where my code is incorrect and/or inadequate, please, and what is required to acchieve my objective?

2. By stepping through the code I start seeing the PWM output as soon as pwmInit() has executed. Do I need to call pwmStart()? If so why?

3. I have trawled the web to find this information so would you also point me to where I can find this (for TMS570LS1224 and N2HET and PWM)?

4. What is the best result that I can expect, in terms of maximum PWM frequency and Duty Cycle?

TIA