SX-Key Error Message: Vpp generation failed.

wbahn

I'm brand new to the SX (have some experience, though dated, with PICs).

I tried to program the part (an SX20) with an SX-Key and got the error that the programming voltage couldn't be generated. I did a search for Vpp in the reference manual and didn't get a single hit.

Anyone have any suggestions?

Is there any place where there is a list of error messages and most likely causes/actions?

TIA
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PJMonty

wbahn,

Is the SX20 in a circuit you designed and built, or someone elses? Are you using a resonator, crystal, or TTL oscillator to provide the clock when the SX-Key isn't present?

Thanks, PeterM

T&E Engineer

You may want to read this thread. The same error came up for me. To summarize: I built my own SX-28 circuit but wired OSC1 and OSC2 from the resonator to OSC2 and OSC1 (respectively) on the SX-28 (basically in reverse).

http://forums.parallax.com/showthread.php?p=600788

r_noble

i had that error only mins ago, and i had my chip in the wrong way

wbahn

Just got back from out of town.

It's a custom design, but someone that is quite experienced with the SX said my schematics are fine. I'm using a CMOS oscillator (which I can enable/disable with a jumper on the board). The footprint I used had the wrong width (too narrow) and so I had to really bend in the pins to get them onto the pads. My plan was to check it closely for shorts this weekend - and based on what has been said here that sounds like the most likely explanation.

Thanks a lot and I'll report back on what I find.

Guenther Daubach

You mentioned a jumper on your board to disable the CMOS oscillator. Make sure that this jumper (when pulled) disconnects the SX OSC1 pin from the rest of the world so that OSC1 is only connected to the SX-Key/Blitz via the 4-pin header.

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Greetings from Germany,

G

wbahn

I looked under the chip with a microscope and, by turning the board on edge, was able to spot a solder bridge between RA0 and OSC1. I don't know what the behavior of the I/O pins is during programming, but RA0 is only connected to the input of another device.

I removed the bridge and it claims to have programmed fine.

In response to your question, Gunther, neither OSC pin is isolated from the rest of the world during programming. I tried to insert a fragment of the schematic in this post but don't know if it will appear or not.

The output of a 50 MHz CMOS oscillator is connected to OSC1 through the series combination of a 0.01uF capacitor and a 330 ohms resistor. Then there is a 1 Mohm resistor connecting OSC1 to OSC2. The programming header connects directly to these pins. My friend said that he has been using this arrangment for years and does not even need to disable the oscillator output. I tried programming the SX again with the oscillator enabled (haven't yet verified that it is actually running, though) and it still appears to have programmed fine.