I have an arduino Uno WiFi Rev2 (ATMEGA4809) and am looking to use the Sparkfun Wireless Motor Driver Shield with it. All my sensors are at a 3.3 volt logic level. If I connected the shield’s IOREF to the Arduino’s 3.3V pin instead of the Arduino’s IOREF, would this cause any problems? I am hoping that I can then use the power and ground supplied to each digital pin for my sensors. And would I need to use a logic level converter in adition to this? or would this replace the need for a logic level converter? Or should I just abandon this idea and use logic level converters for all of the sensors?
Hi clorr.
The IOREF switch is just for the power rail on the shield, it won’t change the voltage the Arduino’s I/O pins run at. You would need logic level converters for your 3.3 volt parts.
Hey Chris, I am also a Chris. Thanks for the reply. If I use a logic level converter for the clock line and use 3.3v instead of IOREF as described previously, I should be able to use the shield’s analogue pins for power, ground, and signal without a converter,correct? Though I realize I would be sacrificing some sensitivity on the inputs, I would be able to get things running ASAP without shelling out $$ for overnight shipping on a second converter.
-Chris
Hello Chris.
IOREF is supposed to tell the shield what voltage the Arduino is using for it’s I/O voltage and then the shield is supposed to setup it’s I/O in accordance but the shield itself doesn’t use IOREF in a standard way. Connecting IOREF to 3.3 volts won’t actually change anything on the shield, the Uno and shield will still operate at 5 volts and have 5 volt I/O.
There are two switches on the shield that allow you to select what voltage appears on the pins labeled PWR on the shield.
(see photo)
That will only affect just the PWR pins and not the actual Arduino pins that are right beside them so A0 - A5 and D0 - D13 will still be operating at 5 volts. If you hook a 3.3 volt part up without a level translator, you could be in for trouble.
What 3.3 volt parts are you trying to connect to the shield? In some limited circumstances you might be able to get away with connecting a 3.3 volt part to a 5 volt pin, but you will still need to power the part with 3.3 volts and the only reliable way to do that would be to connect the parts power pin to the 3.3V pin on the shield. (Not IOREF, that’s not really supposed to be used as a power source)