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MSP430FR5724IRGET Layout for SPI, I2C and VRef

Mobile Wave
Prodigy 130 points
Other Parts Discussed in Thread: MSP430FR5724

Hi,

I am relatively new at using MSP430. My experience with embedded programming so far has been restricted to simple and turnkey Arduino type boards. For my current project, I have to use an MSP430 (FR5724IRGE) as SPI master to control some peripherals, process and output data in I2C and generate a 2.5V reference voltage as reference voltage for peripheral devices. As I am going through the documentation of this device, I need to know the answer to the following questions as I have to create the first rev of PCB pretty soon. I am hoping answers on this forum will help me channelize my research.

1. Do I need an external crystal. In my final application, I need the MSP430 on a small PCB controlling one SPI slave only. My understanding is that it comes with an internal clock that is sufficient for my purpose, but wanted to confirm this.

2. Does this part have a Vref output. The pin out has a Vref+ and Vref- in pins 1&2. I am not sure if these are output or input reference.

3. Which i/o pins should I be using for SPI and I2C. Based on table on page 11 and 12 of the following datasheet, pins 1.6 and 1.7 are to be used for I2C and pins 2.0, 2.1 and 2.2 for SPI data and CLK. 

Thanks a lot for your help.

  • 0
    Guru 74080 points

    1.) No, you do not need an external crystal. For using SPI or I²C the clock accuracy is unimportant. The internal DCO works fine for that.

    2.) This device only has an internal reference with voltages of 1.5, 2.0 and 2.5V - but this is for internal use only and not routed out for external use. The pins 1 and 2 are VeREF- and VeREF+. This "e" means "external" - you can apply a voltage reference to these pins.

    3.) For SPI the pins of UCA0 at P1.5 (CLK), P2.0 (SIMO) and P2.1 (SOMI) are suitable. UCB0 can be used for SPI as well. Here it is P2.2 (CLK), P1.6 (SIMO) and P1.7 (SOMI). When using I²C, then only UCB0 can be used. Then it is P1.6 (SDA) and P1.7 (SCL). And of course you could emulate both in software using any pin of the device.

  • 0 in reply to Dennis Eichmann
    Prodigy 130 points
    Thanks a lot Dennis.

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