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Using SPI mode to interface msp430 with RF transciever and SD card

  1. Aug 14, 2009 #1
    Hi,

    I am planning to use SPI mode to interface a eZ430-RF2500 with a Sandisk Secure Digital Card. The eZ430-RF2500 includes a MSP430 microcontroller and a CC2500 RF transceiver. According to the schematic, the RF transceiver interfaces the MSP430 utilizing the SPI mode, using the SOMI, SIMO, SCK, STE(for chip selecting) pins of MSP430.

    The problem is can I connect the MSP430 with SD card using the same set of input wires(SOMI, SIMO, SCK, STE)? In this case, I suppose MSP430 is the master, both RF transceiver and SD card are slaves. If it is possible, how to use the STE signal to perform slave selecting. ALL the information I've got is that the chip selecting can be done by using the STE, but no detailed examples to demonstrate it.

    Thanks
     
    Last edited: Aug 14, 2009
  2. jcsd
  3. Aug 18, 2009 #2
    You can do daisy chained SPI, although I don't think that is possible in this case.
    I think you can use the STE pin to select between the SD and the CC2500. You have to use a not gate and make sure only one slave is selected at a time.
    connect STE directly to chip select/slave select of cc2500. Use a not gate to connect STE to chip select pin of SD.
    This is not recommended though coz whenever cc2500 is not selected, SD is selected. If you are not aware and send some clk pulses you might end up receiving data from SD.
    Try to use another line to slave select of SD.
     
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