Of course, since I could not get the bootloader running, uploading the code was unsuccessful. I get a warning in Windows that the USB device is not recognized. The LED comes on solid briefly and then goes off. I plugged the other end of the USB directly into the port on the PC. I started the Arduino development environment and loaded a Trinket sketch that had worked on a previous project. I took one out of the package and attached it to a USB cable. I got the new Trinkets today, so I decided to do a simple test. I can't believe that the bootloader is corrupted on both Trinkets, so I am assuming I must be doing something stupid, or forgetting to do something. I attached that one to the cable and got the same results. I have second 5v Trinket the I plan on using for another project. So, it is obviously not ready to receive the sketch. The LED comes on steady for about 2 seconds and then goes off. I believe I followed the instructions closely, as this is not my first Trinket project.

I also noticed that I get a USB error message indicating that the USB device is not recognized, but I think this is a normal message, right?

'avrdude: Error: Could not find USBtiny device (0x1781/0xc9f)' When I try to upload the program, I get an error message: In trying to program the 5v Trinket, I cannot seem to get the onboard LED to pulse. I now want to go to the next step and replace the Uno with the Trinket. I have assembled and tested the RGB-LCD display with backpack using an Uno. I am trying to build the 'Trinket Temperature & Humidity LCD Display' project.

How to wire adafruit trinket 5v guide