I can upload sketches. So it's not a connectivity issue. But I can't upload the GRBL firmware. Error. I tried it on 2 Uno boards. Is it a driver issue? I'm a carpenter. Could I use my hammer to fix it? Please help!
You need to provide details.
What PC operating system?
What version of the Arduino IDE?
What version of GRBL?
What error message are you getting when you try to upload GRBL?
PS ... a mitre saw is more effective than a hammer in cases like this - shorter programs load faster.
It uploads for me.
So you downloaded GitHub - gnea/grbl: An open source, embedded, high performance g-code-parser and CNC milling controller written in optimized C that will run on a straight Arduino as a .zip file using the "Clone or Download" button and selecting "Download as .ZIP"?
And you unpacked the "grbl-master.zip" file?
And you copied the 'grbl' folder (from the expanded grbl-master folder) into the 'libraries' folder of your sketch folder?
And you re-started the Arduino IDE to install the library?
And you selected File->Examples->grbl->grblUpload?
And you selected Tools->Board: "Arduino/Genuino Uno"?
And you connected your Arduino Uno?
And you selected the right serial port under Tools->Port: ?
And you clicked on the Upload button (a circular button with an arrow pointing to the right) at the top of the sketch window?
Then what happened?