I want to make an ATmega (master) talk to another ATmega (slave) over SPI. Since there is only one slave I can get away without using a slave select pin, and simply connecting the slave's SS pin to ground. This saves me a pin on the master device since I don't need a separate pin to drive the slave's SS pin. I tried both implementations and they both work but I was wondering whether they are the same performance wise. In Atmel's AVR151 application note (http://www.atmel.com/images/doc2...) it says "When SS is held low, the SPI is activated and MISO becomes output if configured so by the user." What does it mean for the SPI to become activated in terms of power consumption? Will the slave draw more current when SS is 0 than when it is 1? In this case it might make sense for me to use an extra pin on the master to make sure the SPI is only activated when I want to send or receive data to/from the slave.
Joined: Wed. Oct 8, 2014
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