I invested in Adafruit's Trinket 5v regular board and ran into some annoyances. After reading through A LOT of their forum messages, I found certain little tidbits that seemed to resolve my issues but were not mentioned in the Trinket tutorial. I would like to have these items mentioned in the tutorial, but adafruit doesn't make it easy to contact them and putting this info on the forums is redundant given the info came from the forums in the first place.
- Avoid using pins 3 and 4 during development and testing if at all possible. anything connected to pins 3 and 4 can (and likely will) interrupt the upload. so if you change the code and need to re-upload, it may be painful to constantly disconnect and reconnect wires to these pins. Once I moved my pin 3 wire over to pin 2, I could then use the trinket button to activate the bootloader as the tutorial recommends, the red light would blink as described, and the upload succeeded. Before that, nothing would happen and the red light would just time out.
- Enable Arduino's verbose output setting for uploading. this will make the output skip past the "cannot find USBtiny" message and end with a complete and thank you message. Even though it will complain it can't find a USBtiny, the upload was likely still successful. as long as you followed Adafruit's intro to Trinket tutorial, you should be ok.
- Try to use the tutorial's provided "blink" test code or something similar that is just as simple. Using more complicated code may not provide the immediate confirmation you need to verify the upload is working.