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MSP430FR5738: MCLK, SMCLK and ACLK

Ali Aljumaili
Prodigy 250 points
Part Number: MSP430FR5738
Other Parts Discussed in Thread: MSP-FET

Hi,

I have a question about outputting MCLK, SMCLK and ACLK to pins that are already connected to something else (LED or SPI_CS).

I am using the MSP430FR5738 microcontroller (28 pin QFN package), these GPIOS are currently connected to LEDs (each 50-ohm resistor and a LED). I am setting them as output using the select register with the actual PIN.

Using my oscilloscope, I cannot see any output frequency other than a stable VCC without any oscillation.

Does have a resistor, and a LED connected to that port affect the functionality of being able to output the frequencies? If so how can I check all 3 clock frequencies without physically outputting them to a port?

I am using the MSP-FET and SPY-BI-Wire to debug the MSP430FR5738.


Thanks in advance for answering my beginer question. I also have the schematics attached for reference.

  • 0
    TI__Genius 13215 points
    Hi Ali,

    Sure, the resistor and LED connected to that port affect the functionality of being able to output the frequencies. You should remove the components before measure the frequency on the ports.
    Meanwhile, you should configure the ports for SMCLK/MCLK/ACLK functions instead of GPIO output if you want to measure the clock from the ports. Please find the Peripherals Example for how to configure the ports as clock output, with codes named MSP430FR57xx_CS_0x.c
    dev.ti.com/.../node

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