Problems ISP programming Attiny45 with STK600

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For a while, I was unable to program my Attiny45 AVRs with the STK600. I had no trouble using the STK500 or another device like the AtmelICE directly in circuit but couldn't get it to work with the STK600. I also never had problems programming other AVRs with the STK600.

Today I found out why it doesn't work with the "default" settings. On the Visual Micro forum I read:


Re: Can't upload Arduino sketch to ATtiny chip on STK600 - Blinking RED solution
Reply #14 - Feb 26th, 2020 at 11:56pm Error was for AREF shunts being connected (the way the board ships from factory).  Both AREF0 and AREF1 shunts need to be set over to side (not connected) when using internal AVR reference.  Once removed and STK600 power-cycled, status LED was solid green, and AVR chip communication to AS7 worked perfectly. 

In fact, this situation is noted in the ATK600 User's Guide under "Analog Reference Voltages", but the web-format makes finding information like this very difficult.  Further, the short indication doesn't occur until the AVR is programmed, which is also confusing.


I removed both the AREF0 and AREF1 shunts and now it works just fine. Tough to find.