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AM335x TSC TRM Clarification -- ADC Value Data Format

Hi!

What is the output data format of the TSC_ADC Subsystem?  I know I am about to find out the hard way, but for the sake of future programmers, the answer to the following question is NOT covered in the TRM at all.  There are no (documented) register bits to SET the output data format (the first time I have run into that), nor is there any documentation about what the data format is.

For the sake of future guys like me who are setting up touch-screen and/or other ADC applications, does anyone know the bit pattern to expect from the ADC conversion into the FIFO?  12-bit obviously, but signed?   Unsigned?

Kind regards,
Vic

  • The ADC output is positive binary weighted data ranging from 0 to (2^12 - 1). When configured for single-ended mode, ADC output data values 0 to (2^12 - 1) represents a corresponding input voltage that ranges from the ADC negative reference (REFM) voltage to the ADC positive reference (REFP) voltage. When configured for differential mode, ADC output data values 0 to ((2^12/2) - 1) represents a corresponding negative differential input voltage that ranges from the ADC REFP voltage to the ADC REFM voltage and output data values (2^12/2) to (2^12 - 1) represents a corresponding positive differential input voltage that ranges from the ADC REFM voltage to the ADC REFP voltage.

    You may find additional information, like the information inserted above, in the ADC1 chapter of the AM437x TRM. I was responsable for creating this chapter and tried to clarify some points that were missing from previous versions published in the Touchscreen Controller chapter of AM335x and ADC0 chapter of AM437x.

    Regards,
    Paul

  • Hi, Paul!

    Oustanding and very helpful! And that's great advice too on the AM437x TRM. I didn't even know they were similar. Well done on helping to get the gaps filled in.

    Kind regards,
    Vic