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Wrong feedback of CC2550 working

Slava Apter
Prodigy 40 points
Other Parts Discussed in Thread: MSP430F2111, CC2550

Hi.

I have a system with msp430f2111 and cc2550 ,which is connected by SPI. At the start, i pull low CS line(to enable the transmitter) and i am expecting to receive SO line pull low too, but what i get is opposite thing.SO is going up from 0 to 1.Somebody have any idea, why it happens?

  • 0
    Mastermind 8170 points

    After CS goes low the power is turned on causing SO to go high.  SO then goes low after the XOSC is stable  as a chip ready flag. This is typically tested with a  "while not SO;" loop becuase once it drops it may remain low for a very short time depending on the state of the chip and the following lines of code.  Unless you have a o'scope or logic analyzer on SO you will likely miss it.