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MSP430F2274 question about setting clock for SD Card and USB

ForzaJuve
Intellectual 275 points

Other Parts Discussed in Thread: MSP430F2274, TUSB3410, CC2500

Hi,

I am using MSP430F2274 interfaces with a SD card, I want to write something on the card and read back through USB display the data on Hyper Terminal.

I found SD card and USB share the same clock, which is SMCLK, but using different frequency and baud rate, there's seems a conflict between these two, therefore Hyper Terminal cannot recieve anything from MSP.

Is it possible to make these two work well by using the same clock, same baud rate?

Thank you.

regards.

  • 0
    Guru 17650 points

    Hi ForzaJuve,

    MSP430F2274 has NO USB interface! What you probably mention is the UART connection to the TUSB3410 which is on the eZ430 (the 'debugger part' of the eZ430-RF2500 tool).

    Rgds
    aBUGSworstnightmare 

  • 0 in reply to Joerg Quinten
    Intellectual 275 points

    Yes yes, what I mean is UART and SPI [:P]

    How to make them work together without conflict?

  • 0 in reply to ForzaJuve
    TI__Guru 65060 points

    The MSP430F2274 has 1 USCI peripheral which has 2 ports, the USCI_A0 and USCI_B0.  As you are aware, the USCI_A0 can support UART and SPI, and the USCI_B0 can support SPI and I2C.  Although these 2 portions of the USCI can run at the same time, they do share a common clock.

    Therefore you need to design to the more restrictive interface which would be UART as it requires timing recovery, etc.  The clock into the USCI would need to support an appropriate frequency to generate the right baud rate for the UART interface.  This will then dictate the frequency of the SD card interface using SPI mode.
    Since the MSP430F2274 is the SPI master for the SD card interface, it can dictate the frequency.

  • 0 in reply to BrandonAzbell
    Prodigy 40 points

    If you are using the MSP430F2274 on the EZ430-RF2500, be aware that one of the ports (SPI) is used with the CC2500 and you'll have to alternate between them (using CSn).

    You can't communicate with both at the same time.

     

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