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drivers: pwm: add support for inverted PWM signals

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Add support for requesting an inverted PWM pulse (active-low) when
setting up the period and pulse width of a PWM pin. This is useful
when driving external, active-low circuitry (e.g. an LED) with a PWM
signal.

All in-tree PWM drivers is updated to match the new API signature, but
no driver support for inverted PWM signals is added yet.

All in-tree PWM consumers are updated to pass a flags value of 0
(0 meaning default, which is normal PWM polarity).

Fixes #21384.

Signed-off-by: Henrik Brix Andersen <hebad@vestas.com>
This commit is contained in:
Henrik Brix Andersen 2019-11-13 14:46:37 +01:00 • committed by Carles Cufí
commit db611e6781
24 changed files with 152 additions and 38 deletions
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8
drivers/pwm/pwm_nrfx.c
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@ -123,7 +123,8 @@ static bool any_other_channel_is_active(u8_t channel,
}
static int pwm_nrfx_pin_set(struct device *dev, u32_t pwm,
u32_t period_cycles, u32_t pulse_cycles)
u32_t period_cycles, u32_t pulse_cycles,
pwm_flags_t flags)
{
/* We assume here that period_cycles will always be 16MHz
* peripheral clock. Since pwm_nrfx_get_cycles_per_sec() function might
@ -134,6 +135,11 @@ static int pwm_nrfx_pin_set(struct device *dev, u32_t pwm,
struct pwm_nrfx_data *data = dev->driver_data;
u8_t channel;
if (flags) {
/* PWM polarity not supported (yet?) */
return -ENOTSUP;
}
/* Check if PWM pin is one of the predefiend DTS config pins.
* Return its array index (channel number),
* or NRF_PWM_CHANNEL_COUNT if not initialized through DTS.