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Altera_Forum
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14 years ago

Arduino SPI interface with Cyclone Voltage Issue

Hello guys, I want to interface arduino uno (http://arduino.cc/en/main/arduinoboarduno) via SPI with Altera Cyclone. Arduino can receive Logic VOltage levels of 3.3 with success (mini...
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Altera_Forum
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14 years ago

You do not explain it very well, but I take it from your comment:

(minimum logic '1' is 0.6*5volts(Vcc))

that the Cyclone is actually being operated at 5V.

If the Arduino 3.3V SPI pins are not 5V tolerant (check the PCB design and the Arduino processor datasheet), then you need to drop the voltage on the Cyclone 5V output SPI_MISO. The SPI_SEL and SPI_MOSI from the Arduino will be 3.3V so they will interface to the 5V Cyclone just fine.

How you drop the voltage on the Cyclone 5V output is up to you. If you're just trying to get things working, then a voltage divider is simple. If you are creating an interface board, then you can use a 5V tolerant 3.3V buffer, eg. Tinylogic (from TI, Fairchild, and others). Use Google and you'll find lots of solutions for 5V to 3.3V level translation.

Cheers,

Dave