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AM3354 ADC interface

Andy Pont
Intellectual 380 points
Other Parts Discussed in Thread: AM3354

I am working on a software implementation for a custom hardware platform using the latest Timesys Linux BSP which is derived from the Linux SDK 7.00 release (kernel 3.12).

Could someone explain the difference between the drivers for the ADC interface that can be found as:

Device Drivers -> Multifunction Device Drivers -> TI ADC / Touch Screen Chip Support

and

Device Drivers -> Industrial IO Support -> Analog to Digital converters -> TI's AM335x ADC driver

Also, the company designing the hardware have stated that ADC0 and ADC1 can be configured and used as analogue outputs but I can't find anything in respect of this in either device driver code or documentation.  Have I missed something or have they?

Thanks,

Andy.

  • 0
    TI__Mastermind 25235 points

    Hi Andy,

    Regarding your first question, the ADC driver (TI_AM335X_ADC) and the TSC driver (TOUCHSCREEN_TI_AM335X_TSC) relies on the MFD TSC ADC driver (MFD_TI_AM335X_TSCADC), which enables support for Texas Instruments series of Touch Screen / ADC chips. Check the diagram here: http://processors.wiki.ti.com/index.php/Sitara_TSC_ADC_Driver_Overview

    Best regards,
    Miroslav

  • 0 in reply to Miroslav Kiradzhiyski XID
    TI__Guru 63525 points

    What do you mean by ADC0 and ADC1 in your post?

    AM335x only has one ADC with an 8 to 1 analog multiplexer which allows it to be connected to any one of 8 analog inputs while performing a conversion.

    Is your reference to ADC0 and ADC1 referencing analog inputs AIN0 and AIN1?

    The hardware designer is partially correct. AIN[2:0] can be configured to operate like open-source outputs and AIN[4:1] can be configured to operate like open-drain outputs.  The open-source outputs can source 1.8 volts from the VDDA_ADC terminal and the open-drain outputs can be grounded to the VSSA_ADC terminal  to support touch screen operation.

    See the Analog Front End (AFE) Functional Block Diagram in the TRM.

    Regards,
    Paul

  • 0 in reply to peaves
    Intellectual 380 points

    Hi Paul,

    peaves said:

    What do you mean by ADC0 and ADC1 in your post?

    ...

    Is your reference to ADC0 and ADC1 referencing analog inputs AIN0 and AIN1?

    Sorry for the confusion. I read the signal names off the schematics rather than the pin names from the AM3354 symbol.  Your assumption that ADC0 = AIN0 and ADC1 = AIN1 is correct.

    Thanks for the other information.  I will check that this is the use case the hardware designer was envisaging.

    Andy.