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TMS320F28P550SJ: Certain F28P55x AGPIO pins are not accessible

Sumukh Ananth
Prodigy 140 points
Part Number: TMS320F28P550SJ
Other Parts Discussed in Thread: SYSCONFIG

There are AGPIOs present in P55x, that require the registers AGPIOCTRLx and GPxAMSEL register bits to be set for them to be used as analog pins:
   
However, say I want to use the A15 ADC channel that is a AGPIO pin as shown:
image.png
I cannot use this ADC, as the corresponding bit in AGPIOCTRLx register is Reserved for AGPIO233, and hence not accessible/exposed:
image.png
So, the only way this AGPIO pin can be used as is as a GPIO and not an analog pin, as the GPyAMSEL bit for it is still accessible:
image.png
and is available on the P55x controlCard (no A15 on the Launchpad):
image.png

So, is my understanding correct that AGPIO233 cannot be used as an analog pin and thereby as an ADC, since it's corresponding bit in AGPIOCTRLx register is not accessible?

  • 0
    Prodigy 140 points

    Let me know if you need more info.

  • 0 in reply to Sumukh Ananth
    TI__Expert 4790 points

    Hi Sumukh,

    Apologies for the late reply! Many team members are out of the office this time of year.

    A15 is a valid ADC-capable pad on F28P55x in the packages where it’s bonded out. On AGPIO-type analog pads, the ADC will only see the external signal if the analog path for that pad is connected (AGPIOCTRL bit = 1), and the pad is kept in analog mode (GPxAMSEL = 1).

    So, if you are using a package/board where A15 is actually routed (as you mentioned on the controlCARD), then AGPIO233 should be usable as an ADC input. you just need the right enable sequence.

    There have been known inconsistencies between datasheet/TRM/header files for some of the higher-numbered (analog-shared) GPIOs on F28P55x. You can check the SysConfig for the correct GPIO list while docs/headers get corrected in later releases.

    Best Regards,

    Masoud