The USBTinyISP is a ATtiny44 based ISP (In-System Programmer) board which can be purches for next-to-nothing online.
I followed the Adafruit guide for setting up the board here.
I was attempting to program an ATtiny13 over it's ISP interface.
To do this, within the Arduino IDE (I still use 1.8.5) select
USBtinyISP under the
Tools > Programmer menu.
Once your sketch (program) is ready, you program the target microcontroller using the
Sketch > Upload Using Programmer
Note: that the serial port is not relevant whan programming in this manner.
When I tried to upload my sketch, I was consistently receiving the following failure message in the Arduino IDE terminal.
Programmer Type : USBtiny Description : USBtiny simple USB programmer, http://www.ladyada.net/make/usbtinyisp/ avrdude: programmer operation not supported avrdude: Using SCK period of 10 usec avrdude: error: usbtiny_transmit: avrdude: initialization failed, rc=-1 Double check connections and try again, or use -F to override this check. avrdude: error: usbtiny_transmit:
After exhausting my suspicion that the issue was a bad driver setup,
I moved onto looking at the programmer itself as it was the first time I had used it.
I eventually noticed that the SJFAB jumper was bridged, and when I thought about its name "FAB" stood out... fabrication!
Once I googled SJFAB, I discovered that this jumper is only bridged when loading the firmware onto the ISP istelf, so in my case it shouldn't be bridged.
I believe mine was left bridged in error from the factory.
Once removed, the scketched was programmed into the target micrcontroller immediately!
I hope this helps someone out there who is seeing this failure, as I didn't get clear results when I Googled it.
Good luck with your projects!