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TM4C123GH6PGE: ADC peripheral address defined in code but not datasheet

Michael Michel
Prodigy 30 points
Part Number: TM4C123GH6PGE

Some basics first:

IDE: CCS 7.3

OS: Windows 10

Data Sheet: Tiva™ TM4C123GH6PGE Microcontroller -15033.2672

Board: TM4C123GH6PGE

Code base: TivaWare_C_Series-2.1.4.178

 Problem: I am trying something really simple but its not working (yet).

Here is my diagram:

Here is code I am using. It is taken from :

C:\ti\TivaWare_C_Series-2.1.4.178\examples\peripherals\adc\single_ended.c

 

The only changes I made were to set GPIO_PIN_6 (originally  GPIO_PIN_3).

 

At lines 252 the peripheral is enabled using ip arg “SYSCTL_PERIPH_ADC0”.

It is defined in C:\ti\TivaWare_C_Series-2.1.4.178\driverlib\sysctl.h as

#define SYSCTL_PERIPH_ADC0      0xf0003800  // ADC 0

Question1: But there is no mention , no 0xf0003800 (or even 3800) that I can find in the datasheet. I verified the ADC0 base address but not this “peripheral” address. Where is it?

 

Question2: At line #75 SYSCTL_PERIPH_GPIOE is defined at address 0xf0000804.

Where is it’s corresponding value in the datasheet?

One last thing:

On Page 699, is Register 18 “GPIO Digital Enable (GPIODEN), offset 0x51C”.

It states “By default, all GPIO signals except those listed

below are configured out of reset to be undriven (tristate). Their digital function is disabled…”

Please confirm whether or not I need to set this register

 

  • 0
    TI__Guru 72500 points

    Question1: But there is no mention , no 0xf0003800 (or even 3800) that I can find in the datasheet. I verified the ADC0 base address but not this “peripheral” address. Where is it?

    The value 0xf0003800 is not an address. It is a value used in the function SysCtlPeripheralEnable(). In this case that function writes a "1" to address 0x400FE638  bit 0 to enable ADC0.

    void
SysCtlPeripheralEnable(uint32_t ui32Peripheral)
{
    //
    // Check the arguments.
    //
    ASSERT(_SysCtlPeripheralValid(ui32Peripheral));

    //
    // Enable this peripheral.
    //
    HWREGBITW(SYSCTL_RCGCBASE + ((ui32Peripheral & 0xff00) >> 8),
              ui32Peripheral & 0xff) = 1;
}

    Question2: At line #75 SYSCTL_PERIPH_GPIOE is defined at address 0xf0000804. Where is it’s corresponding value in the datasheet?

    Again, that is not an address.

    On Page 699, is Register 18 “GPIO Digital Enable (GPIODEN), offset 0x51C”. It states “By default, all GPIO signals except those listed below are configured out of reset to be undriven (tristate). Their digital function is disabled…” Please confirm whether or not I need to set this register

    To use a pin as an analog input it is not necessary to set the GPIODEN bit for that pin.

  • 0 in reply to Bob Crosby
    Guru 27665 points

    Bob Crosby said:
    The value 0xf0003800 is not an address.

    Bob Crosby said:
    Again, that is not an address.

    uint32_t for everything strikes again.

    Seriously, this passes up an easy safety check with no gain for not implementing it.

    Robert

  • 0 in reply to Robert Adsett
    Prodigy 30 points
    Hello Robert
    Thank you for the prompt reply.
    Sorry about posting this twice it was late night and after submitting the first post
    I got impatient when there was no response after it was submitted, hence the repeat post.


    Of course you are right about 0xf0003800 not being an address. I need to RTFM (i.e. source code) and driver library better.

    Now is it correct to assume that the example code "single_ended.c" has actually been tested to work on the TIVA DK-TM4C123G?

    I understand slight changes have to be made to verify the correct Port (E) and GPIO 6 (AIN21) pin is used, so can you suggest other aspects of the code that could have been overlooked?

    As of now the ADC code is displays mostly 0's and occasional 1's.

    Thanks

    Mike
  • 0 in reply to Michael Michel
    Guru 27665 points

    Well, my reply was simply to remark that I think the API could use some work with regards to the types used and the effect that has on the ability to detect errors. However you might want to look at your sequence configuration step and check what channel(s) you are configuring.

    Robert