Issues with timer driven ADC which results in improper readings
ADC conversion of 3 channels (where DMA requests are performed in continuous mode) is triggered by Timer 3 Trigger out event. Timer 3 is made to follow a PWM generated by Timer 17 by assigning Timer 17 CCR1 to Timer 3 ARR. To validate the ADC readings, we tried varying Timer 17 PWM from 100 to lower values like 20. While doing so, I noticed that ADC readings are not proper and it varies in opposite direction after crossing a certain duty cycle of 50.
I have configured the ADC and timers using CubeMX and later used HAL library.
Your help and support is greatly appreciated.
Relevant code:
ADC initialization
hadc1.Instance = ADC1;
hadc1.Init.ClockPrescaler = ADC_CLOCK_SYNC_PCLK_DIV4;
hadc1.Init.Resolution = ADC_RESOLUTION_12B;
hadc1.Init.DataAlign = ADC_DATAALIGN_RIGHT;
hadc1.Init.ScanConvMode = ADC_SCAN_ENABLE;
hadc1.Init.EOCSelection = ADC_EOC_SEQ_CONV;
hadc1.Init.LowPowerAutoWait = DISABLE;
hadc1.Init.LowPowerAutoPowerOff = DISABLE;
hadc1.Init.ContinuousConvMode = DISABLE;
hadc1.Init.NbrOfConversion = 3;
hadc1.Init.DiscontinuousConvMode = DISABLE;
hadc1.Init.ExternalTrigConv = ADC_EXTERNALTRIG_T3_TRGO;
hadc1.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_RISING;
hadc1.Init.DMAContinuousRequests = ENABLE;
hadc1.Init.Overrun = ADC_OVR_DATA_PRESERVED;
hadc1.Init.SamplingTimeCommon1 = ADC_SAMPLETIME_160CYCLES_5;
hadc1.Init.SamplingTimeCommon2 = ADC_SAMPLETIME_1CYCLE_5;
hadc1.Init.OversamplingMode = DISABLE;
hadc1.Init.TriggerFrequencyMode = ADC_TRIGGER_FREQ_HIGH;
Timer 3 initialization
htim3.Instance = TIM3;
htim3.Init.Prescaler = 1600 - 1;
htim3.Init.CounterMode = TIM_COUNTERMODE_UP;
htim3.Init.Period = 1;
htim3.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
htim3.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;
if (HAL_TIM_Base_Init(&htim3) != HAL_OK)
{
Error_Handler();
}
sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
if (HAL_TIM_ConfigClockSource(&htim3, &sClockSourceConfig) != HAL_OK)
{
Error_Handler();
}
if (HAL_TIM_OnePulse_Init(&htim3, TIM_OPMODE_SINGLE) != HAL_OK)
{
Error_Handler();
}
sMasterConfig.MasterOutputTrigger = TIM_TRGO_UPDATE;
sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
Timer 17 initialization
htim17.Instance = TIM17;
htim17.Init.Prescaler = 1600 - 1;
htim17.Init.CounterMode = TIM_COUNTERMODE_UP;
htim17.Init.Period = 100 - 1;
htim17.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
htim17.Init.RepetitionCounter = 0;
htim17.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;
if (HAL_TIM_Base_Init(&htim17) != HAL_OK)
{
Error_Handler();
}
if (HAL_TIM_PWM_Init(&htim17) != HAL_OK)
{
Error_Handler();
}
sConfigOC.OCMode = TIM_OCMODE_PWM1;
sConfigOC.Pulse = 0;
sConfigOC.OCPolarity = TIM_OCPOLARITY_HIGH;
sConfigOC.OCNPolarity = TIM_OCNPOLARITY_HIGH;
sConfigOC.OCFastMode = TIM_OCFAST_DISABLE;
sConfigOC.OCIdleState = TIM_OCIDLESTATE_RESET;
sConfigOC.OCNIdleState = TIM_OCNIDLESTATE_RESET;
if (HAL_TIM_PWM_ConfigChannel(&htim17, &sConfigOC, TIM_CHANNEL_1) != HAL_OK)
{
Error_Handler();
}
sBreakDeadTimeConfig.OffStateRunMode = TIM_OSSR_DISABLE;
sBreakDeadTimeConfig.OffStateIDLEMode = TIM_OSSI_DISABLE;
sBreakDeadTimeConfig.LockLevel = TIM_LOCKLEVEL_OFF;
sBreakDeadTimeConfig.DeadTime = 0;
sBreakDeadTimeConfig.BreakState = TIM_BREAK_DISABLE;
sBreakDeadTimeConfig.BreakPolarity = TIM_BREAKPOLARITY_HIGH;
sBreakDeadTimeConfig.BreakFilter = 0;
sBreakDeadTimeConfig.AutomaticOutput = TIM_AUTOMATICOUTPUT_DISABLE;
if (HAL_TIMEx_ConfigBreakDeadTime(&htim17, &sBreakDeadTimeConfig) != HAL_OK)
{
Error_Handler();
}
This was implemented in STM32G030F6P6.
