Posted on June 12, 2015 at 12:02Hi All,
I am learning how the ADCs modes are working on the ST32F4 MCU (using Olimex board). I got operational ADCs (running independently) in
a single a and continuous mode.
The next step is to get a coherent sampling from two ADCs (for all cases I am explicitly polling measurements within my program).
The multimode configuration is presented below. I would like to read the data from both (ADC1 and ADC2) converters into an
array of samples using the following function (S1, S2 are for debugging purposes only):
void Get_RawSamples( __IO uint16_t Ch1[], __IO uint16_t Ch2[], int NumSamples)
{
int16_t i, S1,S2 ;
__IO uint32_t S12;
for (i = 0; i < NumSamples; i++)
{
ADC_SoftwareStartConv(ADC1);
while(ADC_GetFlagStatus(ADC1, ADC_FLAG_EOC) == RESET);
S1 = ADC_GetConversionValue(ADC1);
Ch1[i] = S1;
S2 = ADC_GetConversionValue(ADC2);
Ch2[i] = S2;
}
} /* end Get_RawSamples */
According to the documentation, to retrieve samples from multiple ADCs I should use the
ADC_GetMultiModeConversionValue() function.
When I call the ADC_GetConvertionValue function for each ADC, I am getting correct values (connected a 1.5 V battery, and checked
against the digital multimeter measurements).
When I replace the content of the loop with:
ADC_SoftwareStartConv(ADC1); //this is the master
while(ADC_GetFlagStatus(ADC1, ADC_FLAG_EOC) == RESET);
S12 = ADC_GetMultiModeConversionValue();
and run/debug it, the value of S12 is always zero.
So, I have some questions:
1. If I call ADC_GetConversionValue for each ADC separately do I get coherent measurements ?
2. Why the value of S12 is zero? Is there any special way of dealing with the multimode data conversion?
After getting the ADCs in the polling mode working, I will switch to the DMA approach with timers to control sampling rate.
Thanks in advance for your help.
Cheers,
Darek
P.S. I have noticed that calling:
ADC_EOCOnEachRegularChannelCmd(ADC1, ENABLE)
(or ADC_EOCOnEachRegularChannelCmd(ADC1, DISABLE) for tests)
in the configuration of the ADCs does not have any influence on the behaviour of my code.
/* ADC Configuration */
void Configure_ADCs(void)
{
ADC_InitTypeDef ADC_InitStructure;
ADC_CommonInitTypeDef ADC_CommonInitStructure;
ADC_CommonInitStructure.ADC_Mode = ADC_DualMode_RegSimult;
ADC_CommonInitStructure.ADC_TwoSamplingDelay = 0;
ADC_CommonInitStructure.ADC_DMAAccessMode = ADC_DMAAccessMode_Disabled;
ADC_CommonInitStructure.ADC_Prescaler = ADC_Prescaler_Div2;
ADC_CommonInit(&ADC_CommonInitStructure);
ADC_InitStructure.ADC_Resolution = ADC_Resolution_12b;
ADC_InitStructure.ADC_ContinuousConvMode = DISABLE;
ADC_InitStructure.ADC_ScanConvMode = DISABLE;
ADC_InitStructure.ADC_ExternalTrigConvEdge = ADC_ExternalTrigConvEdge_None;
ADC_InitStructure.ADC_ExternalTrigConv = ADC_ExternalTrigConv_T2_TRGO;
ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;
ADC_InitStructure.ADC_NbrOfConversion = 1;
ADC_Init(ADC1,&ADC_InitStructure);
ADC_Init(ADC2,&ADC_InitStructure);
ADC_RegularChannelConfig(ADC1, ADC_Channel_5,1, ADC_SampleTime_3Cycles);
ADC_RegularChannelConfig(ADC2, ADC_Channel_6,1, ADC_SampleTime_3Cycles);
ADC_Cmd(ADC1,ENABLE);
ADC_Cmd(ADC2,ENABLE);
ADC_EOCOnEachRegularChannelCmd(ADC1, ENABLE);
} /* end Configure_ADCs */
