ADC triger on PWM edge

[Bogdan]

Posted on January 25, 2017 at 22:27

Hello,

On a STM32F407VE device   i have a timer2 which reads 3 hall sensors from a bldc motor,  this timer is feeding the trigger signal into a advanced timer1 which generates 6pwm's for the transistor bridge.

The  reading of the hall sensors and the comutation step configs,  are made inside  the timer2 cc1 irq handler.

The FET signals are TIM_OCMode_PWM1 for high side channels ( CH1, CH2,CH3)    and for low side channel ( CH1N, CH2N, CH3N) its just regular low/high state  

Till here everything is ok, the signals have the corect phase

But i was thinking to ad a current measurement feature  using one ADC channel ( ADC_Channel_14 on PC4 pin) which reads a shunt resistor between low side FET's and ground(GND).

Since i use pwm I was wondering if there is any method using ADC to sync the aquisition trigger on the 'on state' of  the pwm signals?

Do i need DMA for this? since i work only with one physical adc channel

What is.. lets say common practice to configure ADC to capture in sync with pwm 'on time'? Maybe a code reference would be also fit well.

Thank you

[waclawek.jan]

Posted on January 25, 2017 at 22:48

TIM1_CH1/CH2/CH3 can trigger regular conversions, TIM1_CH4 and TIM1_TRGO (which can be set to any channel's compare output) can trigger injected conversions. See Figure 44 in RM0090 rev.13.

JW

[Bogdan]

Posted on January 26, 2017 at 07:54

Hello,

thank you for the information... i have done the following code for ADC initialization

ADC_StructInit(&ADC_InitStructure);

ADC_CommonStructInit(&ADC_CommonInitStructure);ADC_Cmd(ADC1, DISABLE);ADC_DeInit();

NVIC_InitStructure.NVIC_IRQChannel = ADC_IRQn;

NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 4; NVIC_InitStructure.NVIC_IRQChannelSubPriority = 4; NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; NVIC_Init(&NVIC_InitStructure); ADC_CommonInitStructure.ADC_Mode = ADC_Mode_Independent; ADC_CommonInitStructure.ADC_Prescaler = ADC_Prescaler_Div2; ADC_CommonInitStructure.ADC_DMAAccessMode = ADC_DMAAccessMode_Disabled; ADC_CommonInitStructure.ADC_TwoSamplingDelay = ADC_TwoSamplingDelay_5Cycles; ADC_CommonInit(&ADC_CommonInitStructure);

ADC_InitStructure.ADC_Resolution = ADC_Resolution_12b;

ADC_InitStructure.ADC_ScanConvMode = ENABLE; ADC_InitStructure.ADC_ContinuousConvMode = DISABLE; ADC_InitStructure.ADC_ExternalTrigConvEdge = ADC_ExternalTrigConvEdge_Rising; ADC_InitStructure.ADC_ExternalTrigConv = ADC_ExternalTrigConv_T1_TRGO; // external trigger from timer1 TRGO  ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right; ADC_InitStructure.ADC_NbrOfConversion = 1; // 1 channel in total ADC_Init(ADC1, &ADC_InitStructure); ADC_TempSensorVrefintCmd(ENABLE); ADC_InjectedSequencerLengthConfig(ADC1, 0);// Set injected sequencer length ADC_InjectedChannelConfig(ADC1, ADC_Channel_14, 1, ADC_SampleTime_3Cycles); ADC_ExternalTrigInjectedConvConfig(ADC1, ADC_ExternalTrigInjecConv_T1_TRGO); // ADC_ExternalTrigInjectedConvCmd(ADC1, ENABLE); ADC_AutoInjectedConvCmd(ADC1, ENABLE); ADC_ITConfig(ADC1, ADC_IT_JEOC, ENABLE);// Enable injected end of conversion interrupt ADC_Cmd(ADC1, ENABLE); // enable adc

And bellow is the ADC IRQ Handler using the JEOC  IT

void ADC_IRQHandler(void){

if(ADC_GetITStatus(ADC1,ADC_IT_JEOC)){ // end of conversion event

GPIO_ToggleBits(GPIOC, GPIO_Pin_15); // toggle for trace on logic analyzer GPIO_ToggleBits(GPIOC, GPIO_Pin_15); 

// toggle for trace on logic analyzer

value=ADC_GetInjectedConversionValue(ADC1, ADC_InjectedChannel_1);

ADC_ClearITPendingBit(ADC1, ADC_IT_JEOC);// Clear ADC1 JEOC pending interrupt bit }

On the logic analyzer i can see its toggles , but  i tryied to read and convert the value in voltage, and i get 3.2v,  2.6V,  and 0.2V ...  

As seen this on the logic capture, i fear that the adc is trigerd at every hall event, and not at the midle of a pwm ''on cycle''. How to overcome this?

Since i am not familiar with usage of adc injecte mode, i fear i am doing something wrong