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MSP430FR2355: ADCMSC A1 and A4?

Steve Wenner
Genius 3240 points
Part Number: MSP430FR2355


Looking to use the SEEED connector on the EVM.  It is connected to A1 and A4.

First question....Does this particular MSP offer the ability to do repeated conversions on multiple channels that are not ordered?  for instance A1, A4, A2?  I know some of the MSP offer the ability to stack A/Ds in an order that is different than A1, A2, A3, A4, etc.....  It appears not

Question two.....If I cannot just sample A1 and A4 WITHOUT A2 and A3....how am I to configure P1.2 and P1.3 as analog or digital?....Seems that I would be prohibited from using the SEEED connection in analog and I2C (P1.2 / P1.3) at the same time if I cannot ONLY configure A1 and A4 as analog

  • 0
    Guru 100785 points

    1) No. The FR2 ADC (CONSEQ=1/3) always counts down from INCH->A0, in your case A4->A0.

    2) If you use a sequence, including A2/A3, the ADC will sample those pins. The pin schematic in data sheet (SLASEC4D) Fig 6-4 shows that the ADC always has access to the pin. Setting P1SEL=11 doesn't attach the pin to the ADC, it merely conditions the pin for analog. Generally the small sips of current the ADC takes aren't enough to affect digital function.

    One thing to keep in mind about MSC=1 in the FR2 series: There's no DMA, and only one MEM register. If the samples are coming fast, it's difficult to catch one before the next arrives. One solution is to slow the sequence down (using a slow clock or MSC=0 with a timer trigger). But with 5 channels, only 2 of which you're interested in, it might be quicker to just do 2 separate ADC operations (on your schedule) with CONSEQ=0.

  • 0 in reply to Bruce McKenney
    Genius 3240 points

    Thanks...

    Yes most likely I will have to sample A1 then A4 without MSC....I have a switch with pulldown connected to P1.2 (A2) and the schematic shows me using PxSEL will wreak havoc on that....

  • 0 in reply to Steve Wenner
    Guru 100785 points

    Just to be clear: In the sequence case you wouldn't change P1SEL for A2/A3 from what you're doing now. 

    I (still) suspect two individual ADC operations will be better. 

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