ADC STM32F0 DISCO shows big noise

[entwicklung]

Posted on June 11, 2014 at 09:04

Edit: Ok, I used the scope and measured the signals. Actually there is a lot of noise on the inputs. Also connecting the pins directly to ground isn't a good idea as well.

So, I guess this threat can be closed. I'm using the STM32F0308-DISCO and sample data with the ADC at Ports PA4...PA7. It seems like the values are very inacurate and alternating a lot. I connected the pins to ground and got values between 0...2D or similar. If I attach some external voltage the values are getting even worse (for example 2V). I get valuese betweet 0...255 for the low byte. I think there is something wrong with the DMA, because this can't be a hardware issue.

// STM32 ADC 4 Channel DMA/TIM USART2 STM32F0-Discovery sourcer32@gmail.com
#include ''stm32f0xx.h''
//**************************************************************************************
#define SAMPLES 4
volatile uint16_t RegularConvData[SAMPLES];
uint16_t ADC1ConvertedValue1 = 0, ADC1ConvertedValue1_low = 0, ADC1ConvertedValue1_high = 0;
void ADC_TIM_DMA_Configuration(void)
{
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
TIM_OCInitTypeDef TIM_OCInitStructure;
ADC_InitTypeDef ADC_InitStructure;
DMA_InitTypeDef DMA_InitStructure;
/* ADC1 DeInit */
ADC_DeInit(ADC1);
/* ADC1 Periph clock enable */
RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1 | RCC_APB2Periph_TIM1, ENABLE);
/* DMA1 clock enable */
RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);
/* TIM2 Configuration */
TIM_DeInit(TIM1);
/* Time base configuration */
TIM_TimeBaseStructInit(&TIM_TimeBaseStructure);
TIM_TimeBaseStructure.TIM_Prescaler = (SystemCoreClock / 1000000) - 1; // 1 MHz, from 48 MHz
TIM_TimeBaseStructure.TIM_Period = 1000 - 1; // 1 KHz
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseStructure.TIM_ClockDivision = 0;
TIM_TimeBaseStructure.TIM_RepetitionCounter = 0;
TIM_TimeBaseInit(TIM1, &TIM_TimeBaseStructure);
/* Output Compare PWM Mode configuration */
TIM_OCStructInit(&TIM_OCInitStructure);
TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1; /* low edge by default */
TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
TIM_OCInitStructure.TIM_Pulse = 1;
TIM_OC4Init(TIM1, &TIM_OCInitStructure);
/* TIM1 enable counter */
TIM_Cmd(TIM1, ENABLE);
/* Main Output Enable */
TIM_CtrlPWMOutputs(TIM1, ENABLE);
/* DMA1 Channel1 Config */
DMA_DeInit(DMA1_Channel1);
DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)&ADC1->DR;
DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)&RegularConvData[0];
DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;
DMA_InitStructure.DMA_BufferSize = SAMPLES;
DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord;
DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;
DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;
DMA_InitStructure.DMA_Priority = DMA_Priority_High;
DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
DMA_Init(DMA1_Channel1, &DMA_InitStructure);
/* DMA1 Channel1 enable */
DMA_Cmd(DMA1_Channel1, ENABLE);
/* ADC DMA request in circular mode */
ADC_DMARequestModeConfig(ADC1, ADC_DMAMode_Circular);
/* Enable ADC_DMA */
ADC_DMACmd(ADC1, ENABLE);
/* Initialize ADC structure */
ADC_StructInit(&ADC_InitStructure);
/* Configure the ADC1 in continous mode withe a resolutuion equal to 12 bits */
ADC_InitStructure.ADC_Resolution = ADC_Resolution_12b;
ADC_InitStructure.ADC_ContinuousConvMode = DISABLE;
ADC_InitStructure.ADC_ExternalTrigConvEdge = ADC_ExternalTrigConvEdge_Rising;
ADC_InitStructure.ADC_ExternalTrigConv = ADC_ExternalTrigConv_T1_CC4;
ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;
ADC_InitStructure.ADC_ScanDirection = ADC_ScanDirection_Upward;
ADC_Init(ADC1, &ADC_InitStructure);
/* Convert the ADC_Channnel_0 with 7.5 Cycles as sampling time */
ADC_ChannelConfig(ADC1, ADC_Channel_4 , ADC_SampleTime_1_5Cycles);
/* Convert the ADC_Channnel_1 with 7.5 Cycles as sampling time */
ADC_ChannelConfig(ADC1, ADC_Channel_5 , ADC_SampleTime_1_5Cycles);
/* Convert the ADC_Channnel_2 with 7.5 Cycles as sampling time */
ADC_ChannelConfig(ADC1, ADC_Channel_6 , ADC_SampleTime_1_5Cycles);
/* Convert the ADC_Channnel_3 with 7.5 Cycles as sampling time */
ADC_ChannelConfig(ADC1, ADC_Channel_7 , ADC_SampleTime_1_5Cycles);
/* ADC Calibration */
ADC_GetCalibrationFactor(ADC1);
/* Enable ADC1 */
ADC_Cmd(ADC1, ENABLE);
/* Wait the ADCEN flag */
while(!ADC_GetFlagStatus(ADC1, ADC_FLAG_ADEN));
/* ADC1 regular Software Start Conv */
ADC_StartOfConversion(ADC1);
}
//**************************************************************************************
void GPIO_Configuration(void)
{
GPIO_InitTypeDef GPIO_InitStructure;
/* GPIOA Periph clock enable */
RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA, ENABLE);
/* Configure ADC Channels as analog input - might conflict */
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_4 | GPIO_Pin_5 | GPIO_Pin_6 | GPIO_Pin_7;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AN;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
GPIO_Init(GPIOA, &GPIO_InitStructure);
/* Configure USART pins */
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2 | GPIO_Pin_3;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
GPIO_Init(GPIOA, &GPIO_InitStructure);
GPIO_PinAFConfig(GPIOA, GPIO_PinSource2, GPIO_AF_1); // USART2_TX
GPIO_PinAFConfig(GPIOA, GPIO_PinSource3, GPIO_AF_1); // USART2_RX
}
//**************************************************************************************
void USART_Configuration(void)
{
USART_InitTypeDef USART_InitStructure;
RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART2,ENABLE);
/* USART2 9600 8N1 */
USART_InitStructure.USART_BaudRate = 115200;
USART_InitStructure.USART_WordLength = USART_WordLength_8b;
USART_InitStructure.USART_StopBits = USART_StopBits_1;
USART_InitStructure.USART_Parity = USART_Parity_No;
USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;
USART_Init(USART2, &USART_InitStructure);
USART_Cmd(USART2, ENABLE);
}
//**************************************************************************************
char USART_GetChar(void)
{
while(USART_GetFlagStatus(USART2, USART_FLAG_RXNE) == RESET); // Wait For input character
return((char)USART_ReceiveData(USART2));
}
//**************************************************************************************
void USART_PutChar(char ch)
{
while(USART_GetFlagStatus(USART2, USART_FLAG_TXE) == RESET); // Wait for holding buffer empty
USART_SendData(USART2, ch);
}
//**************************************************************************************
void USART_PutString(char *s)
{
while(*s)
USART_PutChar(*s++);
}
//**************************************************************************************
void USART_PutDecimal(unsigned int i)
{
char String[16];
char *s = String + sizeof(String);
*--s = 0; // NUL
do
{
*--s = '0' + (char)(i % 10);
i /= 10;
}
while(i);
USART_PutString(s);
}
//**************************************************************************************
int main(void)
{
GPIO_Configuration();
ADC_TIM_DMA_Configuration();
USART_Configuration();
while(1)
{
char ch;
ch = USART_GetChar();
if (ch == '#')
{
ADC1ConvertedValue1 = RegularConvData[0];
ADC1ConvertedValue1_low = ADC1ConvertedValue1&0xFF;
ADC1ConvertedValue1_high = ADC1ConvertedValue1>>8;
USART_PutChar(ADC1ConvertedValue1_low); // PA7
USART_PutChar(ADC1ConvertedValue1_high);
ADC1ConvertedValue1 = RegularConvData[1]&0xFF;
USART_PutChar(ADC1ConvertedValue1); // PA4
ADC1ConvertedValue1 = RegularConvData[1]>>8;
USART_PutChar(ADC1ConvertedValue1); }
ADC1ConvertedValue1 = RegularConvData[2]&0xFF;
USART_PutChar(ADC1ConvertedValue1); // PA5
ADC1ConvertedValue1 = RegularConvData[2]>>8;
USART_PutChar(ADC1ConvertedValue1);
ADC1ConvertedValue1 = RegularConvData[3]&0xFF;
USART_PutChar(ADC1ConvertedValue1); // PA6
ADC1ConvertedValue1 = RegularConvData[3]>>8;
USART_PutChar(ADC1ConvertedValue1);
}
}
//**************************************************************************************
#ifdef USE_FULL_ASSERT
/**
* @brief Reports the name of the source file and the source line number
* where the assert_param error has occurred.
* @param file: pointer to the source file name
* @param line: assert_param error line source number
* @retval None
*/
void assert_failed(uint8_t* file, uint32_t line)
{
/* User can add his own implementation to report the file name and line number,
ex: printf(''Wrong parameters value: file %s on line %d\r\n'', file, line) */
/* Infinite loop */
while (1)
{}
}
#endif