I got some sparkfun LCD displays (HD44780), but I’m not certain they will work. The datasheet for the Gadgeteer module says 3.3v 0mah, 5.0v 30mah. Does that mean it’s 5V only?
These are the displays I have: https://www.sparkfun.com/products/9052
That means the module is powered by the 5V pin from a gadgeteer mainboard. Interestingly, there is no data sheet for that module on the GHI catalog page. Measure the voltage on the PWR pin to see what the HD44780 IC is putting out. If it’s 5V, I’m not so sure. The datasheet from your display says the following, which seems to imply you may be okay, but more research is a good idea. Best to err on the side of caution.
Just did, 4.81v. Bummer. I suggest they update the store description for this module to be 5V. Unless there is a way to mod it for 3.3V.
Reread my answer… I updated it while you were replying. You may not be totally busted… thoroughly read the HD44780 datasheet for any other clues.
The datasheet for the ST7066 says those voltages, but the datasheet for the LCD it self says max 3.5v. I’ll order some 5V ones. Don’t feel like frying components on a Saturday 
If you don’t want to wait, I have an extra of the 5V ones if you want to drive down my way.
Thanks, but I need 5 of them, so I had to order anyways