Using Asymmetric Mode to generate two phase-shifted waves

[ihottenrott]

I am trying to create two phase-shifted PWM waves on an STM32L4 TIM1 using asymmetric mode. From what I understand, I have to:

enable output on GPIO channels 1 and 3
enable output compare 1,2,3,4 and output compare 1,2,3,4 as asymmetric PWM mode
Then, I set
CCR1 = 0, CCR2 = ARR, and CCR3 and CCR4 to the outputs provided by the function below.

Then I only enable channel 1 and channel 3 as outputs..?
So output compare 1 and 2 work together to produce the first PWM on channel 1. And output compare 3 and 4 work to produce the second PWM on channel 3.

This is what I understand from the graph on page 754 in the RM. But it is not allowing me to change the phase shift while still maintaining 50 % duty cycle on both waves. When I print my CCR3 and CCR4 values, they are exactly ARR apart, which would make me think that they should produce a 50% duty cycle wave. But they don't. 
I'd appreciate any help!

static void tim_phase_shift(uint32_t ARR, float phase_deg, uint32_t *CCR3, uint32_t *CCR4)
{
    uint32_t halfwave = ARR + 1U;
    uint32_t period = 2*halfwave;

    float phase_ticks_f = (phase_deg / 360.0f) * (float)period;
    uint32_t phase_ticks = (uint32_t)(phase_ticks_f + 0.5f); // round

    if (phase_ticks >= period)
        phase_ticks -= period;

    // start of the 50% window, wrapped into [0, halfwave-1]
    uint32_t start = phase_ticks;

    // end of the 50% window is half a virtual period later
    uint32_t stop  = (phase_ticks + halfwave);

    *CCR3 = start;
    *CCR4 = stop;
    printf("ARR = %d\n", ARR);
    printf("CCR3 = %d\n", start);
    printf("CCR4 = %d\n", stop);
}

[TDK]

Are you trying to duplicate this?

Note that CCR3 and CCR4 are not ARR apart.

Should select CCR3 to get the desired phase offset and then set CCR4 = ARR - CCR3.