Stellaris LM4F120XL assigning ADC to GPIO

Quickly - several things:

 a) appears you've correctly enabled the ports bearing potential ADC channels - but never enable the ADC Peripheral itself!  (i.e. SysCtlPeripheralEnable(SYSCTL_PERIPH_ADC0);  // one suspects ADC0 is reasonable choice

b) #include "driverlib/adc.h" should make some appearance - its absence notable...

c) ADC seeks 16MHz System Clock - minimum.  Are you in compliance?

d) your early code does not yet, "ADCSequenceConfigure(), nor ADCSequenceStepConfigure(), nor ADCSequenceEnable()" - all likely required to properly transact w/the ADC.

Such "mixed signal devices" (your MCU) have a fairly complex input circuit arrangement in which a "holding capacitor" charges w/ sampling voltage - which may result from any/all channels which see a voltage introduction.  Thus - your report of some "voltage presence" - upon a "potential" ADC input pin - may not be cause for alarm.

Perhaps a better test would be to complete the ADC initialization process.   (single-ended.c) w/in Examples\Peripherals\ADC\ (my suggestion)  Insure that any/all external voltages you apply are w/in ADC input min/max range - and ideally arise/fall with application of proper power to your MCU...

Thanks, but I initialise the ADC in another part of code before I initialise the GPIO.

int main(void) {
State = Waiting;

// Enable lazy stacking for interrupt handlers. This allows floating-point
// instructions to be used within interrupt handlers, but at the expense of
// extra stack usage.

ROM_FPULazyStackingEnable ();
ROM_FPUEnable ();

//Set up system clock to run at 50MHz
SysClockInit();

//--Initialise screen and display test image
ScreenInit();

//initialise UART0
UARTinit();

//initialise ADC0
ADCinit();

//initialise GPIO peripheral
GPIOinit2();

With GPIO PD0 it's as if there is already a voltage on it before initialisation.

I have just noticed that 3.3V appears on the PD0 pin after I initialise the UART. The code for the UART initialisation is below. I don't see how this should affect pin PD0.

It's all very confusing.

#include "inc/hw_types.h"
#include "inc/hw_ints.h"
#include "inc/hw_memmap.h"
#include "driverlib/sysctl.h"
#include "driverlib/gpio.h"
#include "driverlib/rom.h"
#include "utils/uartstdio.h"
#include "inc/hw_uart.h"
#include "driverlib/interrupt.h"
#include "driverlib/uart.h"
extern char OutBuf[80];
#define byte unsigned char
extern byte OutPtr;

//#define GPIO_PA0_U0RX 0x00000001
//#define GPIO_PA1_U0TX 0x00000401

void UARTinit(void)
{

//initialise UART0
SysCtlPeripheralEnable(SYSCTL_PERIPH_UART0);
SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOA);

GPIOPinConfigure(GPIO_PA0_U0RX);
GPIOPinConfigure(GPIO_PA1_U0TX);
GPIOPinTypeUART(GPIO_PORTA_BASE, GPIO_PIN_0 | GPIO_PIN_1);

SysCtlPeripheralEnable (SYSCTL_PERIPH_GPIOF);
UARTConfigSetExpClk (UART0_BASE, ROM_SysCtlClockGet (), 115200,
(UART_CONFIG_WLEN_8 | UART_CONFIG_STOP_ONE | UART_CONFIG_PAR_NONE));

UARTFIFOLevelSet(UART0_BASE, UART_FIFO_TX4_8, UART_FIFO_RX4_8); // FIFO 8 chars
UARTFIFOEnable(UART0_BASE); //enable FIFOs

IntEnable(INT_UART0); //enable UART interrupt

UARTIntEnable(UART0_BASE, UART_INT_TX);

UARTStdioInit(0); //tells uartstdio functions to use UART0
}

No I wasn't aware of this.

I recant my last note about the UART. It's coming from the step before this, the Initialisation of the Display boosterpack. I'll need to see if the display is already using this pin for something.

Thanks for your help.

Crawford

Your board schematic - identifying the "cross pin" connections (2 of them) should not avoid your attention.

Real thanks results from tick of Verify Answer...  (atop my earlier post - beneficial to future posters who "re-visit" your issue)

Update: 10:56 CST - Verify duly received - acknowledged - and appreciated.  Merci mon ami...