Lost and confused. Bought on Ebay in 2020 as
Here are photos of both sides, can't tell if I run this on 3.3V or 5V. Any help?
TL;DR: you've got a 5V board.
Hi ShermanP -
Yeah, that blink program is probably the best way to tell the difference. I wish there were some other way, like reading a firmware checksum or something. I had to slightly modify the blink example since my project requires knocking off the power and pin-13 LEDs. I use an LED on pin 8 to indicate brief activity. The changes to blink for this are trivial.
Last night I went through the nine Arduinos I have on hand. Three of them are truly 3.3 volt/8 mhz parts. The other six are 5 vā¦
One approach is to apply about 7V between RAW and GND, and measure the voltage regulator output between Vcc and GND. That won't necessarily reveal the oscillator frequency, though.
