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microbit: modified the behaviour of pwm allocation

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Dynamic pwm previously didn't round robin transient pwm channels,
and would therefore bias towards the first transient channel it found.
This update ensures that there is now an equal opportunity for all
channels to be considered for redirection.
This commit is contained in:
James Devine 2016-01-08 18:29:48 +00:00
parent 68474c5e58
commit 643f408ed2
1 changed files with 28 additions and 24 deletions
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52
source/DynamicPwm.cpp
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@ -11,9 +11,9 @@ uint8_t DynamicPwm::lastUsed = NO_PWMS+1; //set it to out of range i.e. 4 so we
* @param pin The pin to start running PWM on
* @param oldPin The pin to stop running PWM on
* @param channel_number The GPIOTE channel being used to drive this PWM channel
*/
*/
void gpiote_reinit(PinName pin, PinName oldPin, uint8_t channel_number)
{
{
// Connect GPIO input buffers and configure PWM_OUTPUT_PIN_NUMBER as an output.
NRF_GPIO->PIN_CNF[pin] = (GPIO_PIN_CNF_SENSE_Disabled << GPIO_PIN_CNF_SENSE_Pos)
| (GPIO_PIN_CNF_DRIVE_S0S1 << GPIO_PIN_CNF_DRIVE_Pos)
@ -37,14 +37,14 @@ void gpiote_reinit(PinName pin, PinName oldPin, uint8_t channel_number)
__NOP();
__NOP();
__NOP();
NRF_TIMER2->CC[channel_number] = 0;
NRF_TIMER2->CC[channel_number] = 0;
}
/**
* An internal constructor used when allocating a new DynamicPwm representation
* @param pin the name of the pin for the pwm to target
* @param persistance the level of persistence for this pin PWM_PERSISTENCE_PERSISTENT (can not be replaced until freed, should only be used for system services really.)
* @param persistance the level of persistence for this pin PWM_PERSISTENCE_PERSISTENT (can not be replaced until freed, should only be used for system services really.)
* or PWM_PERSISTENCE_TRANSIENT (can be replaced at any point if a channel is required.)
* @param period the frequency of the pwm channel in us.
*/
@ -64,15 +64,15 @@ DynamicPwm::DynamicPwm(PinName pin, PwmPersistence persistence) : PwmOut(pin)
* @endcode
*/
void DynamicPwm::redirect(PinName pin)
{
gpiote_reinit(pin, _pwm.pin, (uint8_t)_pwm.pwm);
{
gpiote_reinit(pin, _pwm.pin, (uint8_t)_pwm.pwm);
this->_pwm.pin = pin;
}
/**
* Retrieves a pointer to the first available free pwm channel - or the first one that can be reallocated.
* @param pin the name of the pin for the pwm to target
* @param persistance the level of persistence for this pin PWM_PERSISTENCE_PERSISTENT (can not be replaced until freed, should only be used for system services really.)
* @param persistance the level of persistence for this pin PWM_PERSISTENCE_PERSISTENT (can not be replaced until freed, should only be used for system services really.)
* or PWM_PERSISTENCE_TRANSIENT (can be replaced at any point if a channel is required.)
*
* Example:
@ -90,29 +90,33 @@ DynamicPwm* DynamicPwm::allocate(PinName pin, PwmPersistence persistence)
lastUsed = i;
pwms[i] = new DynamicPwm(pin, persistence);
return pwms[i];
}
}
}
//no blank spot.. try to find a transient PWM
for(int i = 0; i < NO_PWMS; i++)
int channelIterator = (lastUsed + 1 > NO_PWMS - 1) ? 0 : lastUsed + 1;
while(channelIterator != lastUsed)
{
if(pwms[i]->flags & PWM_PERSISTENCE_TRANSIENT && i != lastUsed)
if(pwms[channelIterator]->flags & PWM_PERSISTENCE_TRANSIENT)
{
lastUsed = i;
pwms[i]->flags = persistence;
pwms[i]->redirect(pin);
return pwms[i];
}
lastUsed = channelIterator;
pwms[channelIterator]->flags = persistence;
pwms[channelIterator]->redirect(pin);
return pwms[channelIterator];
}
channelIterator = (channelIterator + 1 > NO_PWMS - 1) ? 0 : channelIterator + 1;
}
//if we haven't found a free one, we must try to allocate the last used...
if(pwms[lastUsed]->flags & PWM_PERSISTENCE_TRANSIENT)
{
pwms[lastUsed]->flags = persistence;
pwms[lastUsed]->redirect(pin);
return pwms[lastUsed];
}
}
//well if we have no transient channels - we can't give any away! :( return null
return (DynamicPwm*)NULL;
}
@ -130,9 +134,9 @@ void DynamicPwm::release()
{
//free the pwm instance.
NRF_GPIOTE->CONFIG[(uint8_t) _pwm.pwm] = 0;
pwmout_free(&_pwm);
pwmout_free(&_pwm);
this->flags = PWM_PERSISTENCE_TRANSIENT;
//set the pointer to this object to null...
for(int i =0; i < NO_PWMS; i++)
if(pwms[i] == this)
@ -153,7 +157,7 @@ void DynamicPwm::release()
*/
PinName DynamicPwm::getPinName()
{
return _pwm.pin;
return _pwm.pin;
}
/**
@ -164,7 +168,7 @@ PinName DynamicPwm::getPinName()
* DynamicPwm* pwm = DynamicPwm::allocate(PinName n);
* pwm->setPeriodUs(1000); // period now is 1ms
* @endcode
*
*
* @note The display uses the pwm module, if you change this value the display may flicker.
*/
void DynamicPwm::setPeriodUs(int period)