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MSP430-F169 - I2C communication to ADC - need to generate a NACK to the slave

Paul15755
Prodigy 10 points

Hello to all,

I'm using a MSP430-F169 and a MAX127 ADC connected via I2C-Bus.

Its easy to read the first correct value from the ADC (two bytes) - but once only. The following received values are all wrong, till I reset the CPU.

From Datasheet ADC:

"After receiving the acknowledge, the slave issues the second byte followed by a NOT acknowledge from the master to indicate that the last data byte has been received. Finally, the master issues a STOP condition, ending the read cycle."

I know, how to generate a STOP condition, but I don't know how to generate a  NOT acknowledge.

Probably this is the reason why it only works once.

Someone knows what to do?

Thanks for your time!

 

 

  • 0
    TI__Guru*** 125430 points

    Use it in the mode where I2CRM=0.  In this setup the I2C peripheral uses the I2CNDAT register to count the number of bytes being received.  The I2C spec requires that a master receiver NACK the last byte received so this will be done by the peripheral automatically.

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