adc problem

canta76 · ‎2011-08-24

Posted on August 25, 2011 at 01:35

Hi all,

I'm trying to work with the ADC of the Discovery board but I've some problem.

At the end of my test I can only read something from an4 to an9.

There is no way to read the first 4 channel, from an0 to an3.

If I connect the pins from ain0 to ain3 to gnd or vcc then the value read is always a random value, the same that I have if I leave the pin floating.

Please help to find a solution......

Here below some lines of my code:

main:

GPIO_DeInit(GPIOE);

GPIO_DeInit(GPIOB);

GPIO_Init(GPIOE, GPIO_PIN_6, GPIO_MODE_IN_FL_NO_IT); //ain9

GPIO_Init(GPIOE, GPIO_PIN_7, GPIO_MODE_IN_FL_NO_IT); //ain8

GPIO_Init(GPIOB, GPIO_PIN_ALL, GPIO_MODE_IN_FL_NO_IT); //ain0-ain7

ADC1_DeInit();

ADC1_Init(ADC1_CONVERSIONMODE_CONTINUOUS,

ADC1_CHANNEL_9,

ADC1_PRESSEL_FCPU_D2,

ADC1_EXTTRIG_TIM,

DISABLE,

ADC1_ALIGN_LEFT,

ADC1_SCHMITTTRIG_ALL,

DISABLE);

ADC1_ScanModeCmd(ENABLE); //ENABLE

ADC1_ITConfig(ADC1_IT_EOCIE,ENABLE);

ADC1_Cmd(ENABLE);

ADC1_StartConversion();

ADC1_ISR:

for(i=0; i<=9;i++)

Conversion_Values[i] = ADC1_GetBufferValue(i);

csr_temp = ADC1->CSR;

csr_temp &= (uint8_t)~ADC1_IT_EOC;

csr_temp |= (uint8_t)(ADC1_CHANNEL_9);

ADC1->CSR = csr_temp;

ADC1_StartConversion();

brazov22 · ‎2011-08-25

Posted on August 25, 2011 at 09:37

1. Check cpu clock frequency and adc prescaler settings. ADC clock max frequency can't be exceeded (see datasheet).

2. Try to replace last part of your code with the following one:

// Wait until the conversion is done (no timeout => ... to be done)

while ( ADC1_GetFlagStatus(ADC1_FLAG_EOC) == RESET );

// EOC <- 1 then retrieves data from ADC buffers

for (i=0; i<9; i++)

Conversion_Values [9+i] = (unsigned int)ADC1_GetBufferValue(i); // 10 bit

// SW Clear the EOC flag to get the ADC ready for the next start conversion command

ADC1_ClearFlag(ADC1_FLAG_EOC);

ADC1_StartConversion();

brazov2