In SX Microcontrollers, SX/B Compiler and SX-Key Tool, william wrote:

You know I have been having "SX-Key not found on COM1" problems with my SX-Key rev. E for a long time with nobody being able to help.

So, I finally decided to do something about it once and for all.
I went out and bought a $600 digital bench power supply and used it to power my numerous projects that couldn't be programmed by SX-Key rev E but can be programmed by SX-Key rev F.

And guess what, it works all the time now using the bench power supply.
I switched back to the Made in China 12V adapter, the SX-Key rev F cannot program again, even if you try 10 times.
I have 5 different brands of 12V adapters, all of them doesn't work with SX-Key rev E on many projects.

So, the conclusion is SX-Key rev E requires a very stable (ripple free?) power supply wheareas SX-Key rev F is more accomodating.
Any explanations from Parallax engineers?

All my mentioned projects use 7805 regulators, converting 12V to 5V.
I always place a 450uF Cap before the 7805 and a 220uF Cap plus a 0.47uF Ceramic cap on the 5V rail.
How to make the supply more acceptable to SX-Key Rev E?

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