Impossible to use ADC on several channels (repost)

[bruno239955_stm1_stmicro]

Posted on October 06, 2009 at 13:19

Impossible to use ADC on several channels (repost)

[bruno239955_stm1_stmicro]

Posted on May 17, 2011 at 15:05

Hi,

Something goes wrong with the forum. Please discard my previous message and read this one:

I am writing an application with STM8S208RB on the Raisonance REva evaluation board. I read analog values from entries IN1, IN2, potentiometer and temperature sensor (on PF4-7).

I use single conversion, no IT, no Schmidt trigger. Everything is simple, except that I need to be able to read any one of the entries above when I need it.

I wrote a simple application that does just that, but the values that I read from the ADC change in an inconsistent manner. I spent quite some time trying to understand what happens, and the ST library examples work well.

Following is the faulty code. I attach a zip file with the Ride7 project so that you can experiment wil the full project.

Can anyone see what is the problem?

Thanks for your Help,

Bruno

#include

#include ''stm8s.h''

/**

* Analog I/Os are as follows on the STM8S208 daughterboard:

* IN1 PF.4 - External analog input

* IN2 PF.5 - External analog input

* TEMP PF.6 - Temperature sensor analog input

* POT PF.7 - Potentiometer analog input, min=0V, max=VDD

*/

#define CHANNEL_IN1 ADC2_CHANNEL_12

#define CHANNEL_IN2 ADC2_CHANNEL_13

#define CHANNEL_TEMP ADC2_CHANNEL_14

#define CHANNEL_POT ADC2_CHANNEL_15

#define MAX_ADC_VAL 0x3FF /* 10-bit ADCs */

/**

* Voltage (in mV) of the Vcc of the Daughterboard.

* This (global) variable is used in the voltage conversions from the ADC

* for the conversion between the ADC range to the required voltage.

* The default value is 4700 (4.7V).

*/

unsigned short VDDmV = 4700;

/**

* @brief Initializes ADC2 inputs for PF.4-7

* @param None

* @retval None

*/

void ADC_Init(void)

{

/* Init GPIO for ADC2 */

GPIO_Init(GPIOF, GPIO_PIN_4 | GPIO_PIN_5 | GPIO_PIN_6 | GPIO_PIN_7, GPIO_MODE_IN_FL_NO_IT);

/* ADC2 configuration */

ADC2_DeInit();

/* Disable interrupts */

ADC2_ITConfig(DISABLE);

}

/**

* Read the value from a given channel

* @param channel The channel number to read from

* @retval The analog value read (in mV)

*/

unsigned short ADC_ReadChannel(unsigned char channel)

{

unsigned short val;

/* Configure ADC2 for a single capture on given channel */

ADC2_Init(ADC2_CONVERSIONMODE_SINGLE,

channel,

ADC2_PRESSEL_FCPU_D2,

ADC2_EXTTRIG_TIM,

DISABLE,

ADC2_ALIGN_RIGHT,

channel,

DISABLE);

ADC2_Cmd(ENABLE);

ADC2_StartConversion();

/* Wait for end of conversion */

while(ADC2_GetFlagStatus() == RESET)

;

val = ADC2_GetConversionValue();

ADC2_Cmd(DISABLE);

ADC2_ClearFlag();

return val;

}

void main(void)

{

ADC_Init();

while(1)

{

printf(''I1 = %04x '', ADC_ReadChannel(CHANNEL_IN1));

printf(''I2 = %04x '', ADC_ReadChannel(CHANNEL_IN2));

printf(''POT = %04x '', ADC_ReadChannel(CHANNEL_POT));

printf(''TEMP = %04x\n'', ADC_ReadChannel(CHANNEL_TEMP));

}

}