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

Sylvie,

seems as if JonnyMack is right and your Key is bad.

The part marked "220" is an inductor used to generate Vpp, the programming voltage. When this inductor gets hot, it is most likely that the transistor driving the inductor has a short, causing current constantly flowing through the inductor. So, it is a good idea getting in touch with the Parallax support.

Some other comments:

The "Vpp generation failed" error comes up when the on-board SX20 detects that the programming voltage of about 12 Volts (also generated under control of the SX20) is not available. Possible causes can be a short, or an excessive load between the OSC1 pin and Vss, or a bad SX-Key.

The length of the wires you are using for your prototype is not critical as long as you use the SX-Key for programming the SX only. Signal frequencies during programming are relatively low. When you want to debug the chip, you should consider using a setup with shorter wires as much higher signal frequencies are generated by the SX-Key then.

For programming the SX, it is most important that the MCLR pin is pulled up to Vdd. A resistor in series, like 10 kOhm protects the MCLR input when Vdd by some reason exceeds the maximum value of 7 Volts. The same is true for all other SX input pins. When a pin shall be tied to "low", you can always connect it to Vss. When it shall be tied to "high", use a resistor to connect a pin to Vdd.

The SX-Key USB is powered from the USB port, so there is no need to feed through Vdd from the device under test to the SX-Key. When you are using any other device, like the SX-Blitz USB, or the older serial SX-Key/Blitz devices, it is necessary to feed through Vdd from the device unter test to the SX-Key/Blitz.

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