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Thread: XMC1100 ADC Problem with setting Gain

  1. #1
    New Member New Member Samuel is on a distinguished road
    Join Date
    Jan 2019

    XMC1100 ADC Problem with setting Gain

    Hello everyone,

    I have a XMC1100 Boot Kit (KIT_XMC11_BOOT_001) and would like to use its ADC with a gain of 12.
    I have tried to configure the ADC with Dave and added an ADC_MEASURMENT APP, but there is no option for setting gain there.
    So i tried it without gain at first and the measurement works, but I do need the gain.
    So after that I found the function "XMC_VADC_GLOBAL_SHS_SetGainFactor" in the xmc_vadc module and tried using that, but when stepping into the function in debug mode i noticed that writing to the Gain control register GNCTR00 doesnt seem to work. The value of the register (in the "Expressions" window of Dave) doesnt change.
    Specifically, i am using: XMC_VADC_GLOBAL_SHS_SetGainFactor(GLOBAL_ADC_0.glo bal_shs_ptr, 3, XMC_VADC_GROUP_INDEX_0, 2);
    I also tried directly setting the GNCTR00 register this way: GLOBAL_ADC_0.global_shs_ptr->GNCTR00 |= ((uint32_t)3 << 8);
    But neither of those change the value in GNCTR00.
    So i took a look at the datasheet and found that the gain control register is supposed to be at the memory address 0x48034180. I entered that address into the memory watch window and found out that the contents of this register are as follows:
    Address 0 - 3 4 - 7 8 - B C - F
    48034180 ???????? ???????? ???????? ????????
    As far as i know, this means that there is nothing at this register. That would explain why i cant successfully write to it, but the Datasheet says that there should be something there, so i am a bit confused.
    So what am i missing here? Does the Chip not have settable gain after all? Am i just looking at the wrong function, or using it incorrectly?

    Best regards,

    EDIT: Nevermind, I got it to work after all.
    I added the line:
    SHS0->GNCTR00 |= ((uint32_t)3 << 8);
    at line 231 of xmc_vadc.c
    and tested it by applying the same voltage to two different ADC channels, which gave different results by the expected factor.
    I´d still like to know how to write to that register from my main file, but its not that important now.
    Last edited by Samuel; Jan 4th, 2019 at 11:29 AM.

  2. #2

    Infineon Employee
    Infineon Employee
    jferreira will become famous soon enough
    Join Date
    Oct 2012

    Actually the structure member global_shs_ptr is not initialized properly by the APP in the case of XMC11
    We will fix it in the next release.

    The views expressed here are my personal opinions, have not been reviewed or authorized by Infineon and do not necessarily represent the views of Infineon.

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