TivaC sample ADC code problem

[nesslersreagent 0]

Hi,

 

I've recently upgraded my Energia IDE to the latest release 0101E0011. I'm using the Stellaris Launchpad with lm4f120h5qr.
My sample ADC code doesn't seem to work right. Worked well in the previous release of Energia.

The code compiles properly but does not produce the right output.

The only changes made were to change "ADC_BASE" to "ADC0_BASE" as required.
 

I've added Serial output code for debugging purposes.

The serial output produced is:

1

2

3

Code:

#include "Energia.h"
#include "driverlib/sysctl.h"
#include "driverlib/adc.h"

void setup()
{
  Serial.begin(115200);
  
  Serial.println("1");
  //enable the adc0 peripherial.
  SysCtlPeripheralEnable(SYSCTL_PERIPH_ADC0);
  Serial.println("2");
  //set the speed to 1msps.
  SysCtlADCSpeedSet(SYSCTL_ADCSPEED_1MSPS);
  Serial.println("3");
  //set the auto avergage to 64.
  ADCHardwareOversampleConfigure(ADC0_BASE, 64);
  Serial.println("4");
  //before setting up I must disable the sequence 3.
  ADCSequenceDisable(ADC0_BASE, 3);
  Serial.println("5");
  //set the sequence to use (adc0 sequence 3).
  ADCSequenceConfigure(ADC0_BASE, 3, ADC_TRIGGER_PROCESSOR, 0);
  Serial.println("6");
  //set up the sequence step.
  //set up the last step and start an interrupt when the conversion it's over.
  ADCSequenceStepConfigure(ADC0_BASE, 3, 0, ADC_CTL_TS | ADC_CTL_IE | ADC_CTL_END);
  Serial.println("7");
  //enable the sequence again!
  ADCSequenceEnable(ADC0_BASE, 3);
  Serial.println("8");
}

void loop()
{
}

[energia 485]

I don't have access to hardware right now but as soon as I do I will give this a try. Just for kicks, what happens if you stick the code into the loop() and do a while(1) at the end?

[Lyon 3]

Hi,

Two problems with your code:

1) First, you should have a GPIO peripheral enabled and a specific pin configured as analog input pin. 

2) In this function call
    ADCSequenceStepConfigure(ADC0_BASE, 3, 0, ADC_CTL_TS | ADC_CTL_IE | ADC_CTL_END);

the pin selected for conversion is still the internal temperature sensor (ADC_CTL_TS) - replace it with your analog pin declared above. Also, you don't need to declare ADC_CTL_IE if you do not use ADC interrupts.

 

L

[nesslersreagent 0]

Hi,

I have modified the code as per Lyon's suggestions and it works! Thanks.

Also I've realised that the ADC speed must be changed before the ADC peripheral is enabled. This was the prime cause of all my troubles.

 

Output:

1

2

3

4

5

6

7

8

 

Code:

#include "Energia.h"
#include "driverlib/sysctl.h"
#include "driverlib/adc.h"

void setup()
{
  Serial.begin(115200);
  
  Serial.println("1");
  //set the speed to 1Msps.
  SysCtlADCSpeedSet(SYSCTL_ADCSPEED_1MSPS);
  //enable the adc0 peripherial.
  Serial.println("2");
  SysCtlPeripheralEnable(SYSCTL_PERIPH_ADC0);
  SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOE);
  GPIOPinTypeADC(GPIO_PORTE_BASE, GPIO_PIN_0 | GPIO_PIN_1 | GPIO_PIN_2 | GPIO_PIN_3);
  Serial.println("3");
  //set the auto avergage to 64.
  ADCHardwareOversampleConfigure(ADC0_BASE, 64);
  Serial.println("4");
  //before setting up I must disable the sequence 3.
  ADCSequenceDisable(ADC0_BASE, 3);
  Serial.println("5");
  //set the sequence to use (adc0 sequence 3).
  ADCSequenceConfigure(ADC0_BASE, 3, ADC_TRIGGER_PROCESSOR, 0);
  Serial.println("6");
  //set up the sequence step.
  //set up the last step and start an interrupt when the conversion it's over.
  ADCSequenceStepConfigure(ADC0_BASE, 3, 0, ADC_CTL_CH0 | ADC_CTL_END);
  Serial.println("7");
  //enable the sequence again!
  ADCSequenceEnable(ADC0_BASE, 3);
  Serial.println("8");
}

void loop()
{
}

[Lyon 3]

Hi,

You need to know also this:

http://e2e.ti.com/support/microcontrollers/tiva_arm/f/908/t/293858.aspx

Also, if Adc speed needed is 1M, then this is default at startup and can be omitted from setings.

L

[energia 485]

Thanks @@Lyon for solving this one!

[nesslersreagent 0]

Thanks Lyon for your help. Most helpful.

[rnightbane 0]

Hi!

 

How do you access the result of the ADC? Given that you put an input analog signal on the GPIO pin...

[energia 485]

uint16_t value[1];
ROM_ADCSequenceDataGet(ADC0_BASE, 3, (unsigned long*) value)

Also see wiring_analog.c for examples.

 

If you do not need special sequencing, etc then use the build in analogRead().

 

Robert

[rnightbane 0]

#include "Energia.h"

#include "driverlib/sysctl.h"

#include "driverlib/adc.h"

#define A3 PE_0

 

 

void setup()

{

 

  Serial.begin(512000);

  

  SysCtlADCSpeedSet(SYSCTL_ADCSPEED_1MSPS);

  

  SysCtlPeripheralEnable(SYSCTL_PERIPH_ADC0);

  

  SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOE);

  

  GPIOPinTypeADC(GPIO_PORTE_BASE, GPIO_PIN_0);

  

  ADCHardwareOversampleConfigure(ADC0_BASE, 64);

  

  ADCSequenceDisable(ADC0_BASE, 3);

  

  ADCSequenceConfigure(ADC0_BASE, 3, ADC_TRIGGER_PROCESSOR, 0);

  

  ADCSequenceStepConfigure(ADC0_BASE, 3, 0, ADC_CTL_CH0 | ADC_CTL_END);

  

  ADCSequenceEnable(ADC0_BASE, 3);

  

}

 

void loop()

{

  int f;

  

  ADCProcessorTrigger(ADC0_BASE, 3);

  

  f = analogRead(A3);

 

  Serial.write(f);

  

}

 

thanks for answering my question...

 

i modified a bit of his code, and placed analogRead() in place of AnalogSequenceGet(), so is my pin for analogRead() right? Since I assumed that PE_0 is the ADC pin used...

[energia 485]

You do not need to setup the ADC when using analogRead(). The Sketch below should do what you are looking for. PE_0 is indeed ADC channel 3 as per the pin map posted here: http://energia.nu/Guide_StellarisLaunchPad.html

#include "Energia.h"

void setup()
{
  Serial.begin(512000);
}
 
void loop()
{
  int f;
  f = analogRead(A3);

  Serial.write(f);
}

[rnightbane 0]

I see, but what if I want to change the ADC speed, how do I change it if analogRead() already has its ADC set up as it is? And how many bits does the ADC transfer to UART?