Hi,
i have a custom design with a STSPIN32G4 SoC. However, I think my question does refer to the internal microcontroller (STM32G431VBTx) and not the motor controller.
- Timer TIM3 does trigger an interrupt every 10 ms.
- The Interrupt starts a conversion of ADC2, which reads the channels IN3 (single ended), IN4 (signle ended), IN8 (single ended), and VOPAMP3 channel
- A single conversation should take about 60 µs (ADC_CLK = 170 MHz / 4; 640.5 Cycles per Channel; 4 * 640.5 / 42.5 MHz = 60 µs)
- VOPAMP3 is configured as PGA Internally Connected with a gain factor of 32.
- The measured voltages of IN3, IN4, and IN8 are ok.
- The output voltage of VOPAMP3 is different than expected.
- According to the datasheet of the microcontroller (5.3.22 Operational amplifiers characteristics) the OPV has
- an input common mode range from 0 to VDDA
- a maximum offset Voltage of 3 mV over the entire temperature range
- the low saturation voltage is at 100 mV
-
- I would expect the maximum measured output voltage to be somewhere around 3 mV * 32 (PGA gain) = 96 mV
- The adc reads a voltage of 450 mV.
Do you have any ideas what can cause this issue?
I initialize the OPV with CubeMX generated Code:
hopamp3.Instance = OPAMP3;
hopamp3.Init.PowerMode = OPAMP_POWERMODE_NORMALSPEED;
hopamp3.Init.Mode = OPAMP_PGA_MODE;
hopamp3.Init.NonInvertingInput = OPAMP_NONINVERTINGINPUT_IO0;
hopamp3.Init.InternalOutput = ENABLE;
hopamp3.Init.TimerControlledMuxmode = OPAMP_TIMERCONTROLLEDMUXMODE_DISABLE;
hopamp3.Init.PgaConnect = OPAMP_PGA_CONNECT_INVERTINGINPUT_NO;
hopamp3.Init.PgaGain = OPAMP_PGA_GAIN_32_OR_MINUS_31;
hopamp3.Init.UserTrimming = OPAMP_TRIMMING_FACTORY;
if (HAL_OPAMP_Init(&hopamp3) != HAL_OK)
{
Error_Handler();
}
I initialize the ADC with CubeMX generated Code:
hadc2.Instance = ADC2;
hadc2.Init.ClockPrescaler = ADC_CLOCK_SYNC_PCLK_DIV4;
hadc2.Init.Resolution = ADC_RESOLUTION_12B;
hadc2.Init.DataAlign = ADC_DATAALIGN_RIGHT;
hadc2.Init.GainCompensation = 0;
hadc2.Init.ScanConvMode = ADC_SCAN_ENABLE;
hadc2.Init.EOCSelection = ADC_EOC_SINGLE_CONV;
hadc2.Init.LowPowerAutoWait = DISABLE;
hadc2.Init.ContinuousConvMode = ENABLE;
hadc2.Init.NbrOfConversion = 4;
hadc2.Init.DiscontinuousConvMode = DISABLE;
hadc2.Init.ExternalTrigConv = ADC_SOFTWARE_START;
hadc2.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE;
hadc2.Init.DMAContinuousRequests = DISABLE;
hadc2.Init.Overrun = ADC_OVR_DATA_PRESERVED;
hadc2.Init.OversamplingMode = DISABLE;
if (HAL_ADC_Init(&hadc2) != HAL_OK)
{
Error_Handler();
}
/** Configure Regular Channel
*/
sConfig.Channel = ADC_CHANNEL_3;
sConfig.Rank = ADC_REGULAR_RANK_1;
sConfig.SamplingTime = ADC_SAMPLETIME_640CYCLES_5;
sConfig.SingleDiff = ADC_SINGLE_ENDED;
sConfig.OffsetNumber = ADC_OFFSET_NONE;
sConfig.Offset = 0;
if (HAL_ADC_ConfigChannel(&hadc2, &sConfig) != HAL_OK)
{
Error_Handler();
}
/** Configure Regular Channel
*/
sConfig.Channel = ADC_CHANNEL_4;
sConfig.Rank = ADC_REGULAR_RANK_2;
if (HAL_ADC_ConfigChannel(&hadc2, &sConfig) != HAL_OK)
{
Error_Handler();
}
/** Configure Regular Channel
*/
sConfig.Channel = ADC_CHANNEL_8;
sConfig.Rank = ADC_REGULAR_RANK_3;
if (HAL_ADC_ConfigChannel(&hadc2, &sConfig) != HAL_OK)
{
Error_Handler();
}
These are the functions I use to read out the adc. Before I do anything with the peripherals I give the MCU 100 ms to settle.
HAL_OPAMP_SelfCalibrate(&hopamp3);
HAL_OPAMP_Start(&hopamp3);
HAL_ADCEx_Calibration_Start(&hadc2, ADC_SINGLE_ENDED);
// Retriggered in TIM3 Callback
HAL_ADC_Start_DMA(&hadc2, (uint32_t*)&adc_buffer, 4);
Best regards.
