Beginner's question - programming failure
sylvie369
Posts: 1,622
Okay, I got an SX-Key in the daily deal, and a couple of SX-28 DIP chips. I thought I could use the SX-Key to program the chips in a breadboard, but it's not working as I'd hoped. I'm getting a "Vpp generation failure" each time I try to program the chip. In addition, the SX-Key gets hot.
First question: am I wrong in my assumption that this can work?
If not, then here's what I've got (see photo - ignore the 8-pin DIP on the power supply breadboard - it's just resting there):
A wire from OSC1 of the SX-Key to pin 27 of the SX 28.
A wire from OSC2 of the SX-Key to pin 26 of the SX 28
A wire from VSS on the SX-Key to pin 4 of the SX 28
A wire from pin 2 of the SX 28 to pin 28 of the SX 28.
(I have also tried this with a 10K resistor from pin 28 to Vcc instead, with the same results)
I have a 5V breadboard supply, +5V going into pin 2 of the SX 28, ground going into pin 4 of the SX 28. I have checked the supply, and I am getting 5V. I have traded it out with another 5V supply (from a Stamp protoboard) with the same results. I have put a voltmeter on the actual SX 28 pins 2 and 4 to make sure the power is getting there: it is. I read 5V across them.
As I understand it, a Vpp generation failure refers to the inability to generate the voltage needed for programming. Is this perhaps just inadequate power supply?
Post Edited (sylvie369) : 7/3/2009 8:25:38 PM GMT
First question: am I wrong in my assumption that this can work?
If not, then here's what I've got (see photo - ignore the 8-pin DIP on the power supply breadboard - it's just resting there):
A wire from OSC1 of the SX-Key to pin 27 of the SX 28.
A wire from OSC2 of the SX-Key to pin 26 of the SX 28
A wire from VSS on the SX-Key to pin 4 of the SX 28
A wire from pin 2 of the SX 28 to pin 28 of the SX 28.
(I have also tried this with a 10K resistor from pin 28 to Vcc instead, with the same results)
I have a 5V breadboard supply, +5V going into pin 2 of the SX 28, ground going into pin 4 of the SX 28. I have checked the supply, and I am getting 5V. I have traded it out with another 5V supply (from a Stamp protoboard) with the same results. I have put a voltmeter on the actual SX 28 pins 2 and 4 to make sure the power is getting there: it is. I read 5V across them.
As I understand it, a Vpp generation failure refers to the inability to generate the voltage needed for programming. Is this perhaps just inadequate power supply?
Post Edited (sylvie369) : 7/3/2009 8:25:38 PM GMT
3264 x 2448 - 2M
Comments
I had this happen to me once.
Is it heating up immediately on power up, or when you try to prog. it?
- Howard
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-- you *must* use 10k to tie the /MCLR high, not a straight connection to Vdd.
-- suggest tying pin 1 (RTCC in) to 5v also
-- you are using the USB Key? If so, other then the two items above, your setup looks OK
Vpp generation failure and/or failure to connect can sometimes be due to dirty connections. Have you tried using the DEVICE window to READ the chip rather than programming? This will at least let you test your setup before programming (and possible failures).
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When the going gets weird, the weird turn pro. -- HST
1uffakind.com/robots/povBitMapBuilder.php
1uffakind.com/robots/resistorLadder.php
I had your same troubles·and it was because the power supply was inadequate (imagine), the SX lock up and get hot that way.·
Found a gap in my "current limit" pot which made it limit out early.
Leon
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Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle
The connection to OSC1/OSC2 should be close
to the pins.
regards peter
[noparse][[/noparse]Edit] I see that Zoot pointed out the 10K pullup on /MCLR -- it was good advice then, too!
I also traded out SX chips in case I'd fried the first one,· but that also did not make a difference.
I also think that the SX-Key was getting hot just from being plugged into the USB port. I've disconnected it and let it cool down, and just reconnected it with no circuitry attached. Sure enough, it gets hot without being plugged into anything other than the USB port. Surely that's not normal?
Let's give it one more shot here to cool down, and then try that again. Okay, yup, it definitely gets hot from just being plugged into the USB port. The heat is coming from the object marked "220", which I assume is the voltage regulator. It's heating up inside of a minute, with no attempt to program or anything like that.
Whaddya all think?
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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Greetings from Germany,
G
I'll talk with support and see what they say.
Apparently the first one did have a short of some kind, but you couldn't ask for better customer service. Thanks, Joshua.
Thanks also to those who sent along hints here. In particular, I'll redo my setup using pin headers instead of long wires.