What have I done wrong to fry my SX ?
EWo_Ge
Posts: 20
I'm working on a small project to generate a coupple of PULSOUT signals.
I have a SX28 on a small board, some connectors and a LED with 230 Ohm to +5V.
The LED is more or less just as pulsing indicator for the function of the controller.
After soldering the circuit, I took the usual precautins like measuring for shorts and right voltage on the right pins etc.
I downloaded first a small test programm, which is doing nothing but a pulsing output to the LED. I'm·using·the internal oscillatar with 4 MHz.
So far everything worked fine. After·disconnecting SX Key and power I reconnected only the power and the LED started pulsing as planned and expected.
When I then reconnected the SX Key to download another programm, the LED stayed on, the chip got warm and is not talking to me since.
What went wrong ???
Thanks for any help,
EWo
I have a SX28 on a small board, some connectors and a LED with 230 Ohm to +5V.
The LED is more or less just as pulsing indicator for the function of the controller.
After soldering the circuit, I took the usual precautins like measuring for shorts and right voltage on the right pins etc.
I downloaded first a small test programm, which is doing nothing but a pulsing output to the LED. I'm·using·the internal oscillatar with 4 MHz.
So far everything worked fine. After·disconnecting SX Key and power I reconnected only the power and the LED started pulsing as planned and expected.
When I then reconnected the SX Key to download another programm, the LED stayed on, the chip got warm and is not talking to me since.
What went wrong ???
Thanks for any help,
EWo
Comments
Bean.
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Never argue with an idiot.· They'll drag you down to their level then beat you with experience.
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I have to admit, that I'm not sure about that. Is there a specific sort of order to I should dis- and reconnect power and SX-Key?
After I removed the toasted chip and soldered in a socket (which I tried to prevent at first) I made a second attempt. The result were unfortunatly the same...
To my defense, that was before I read your reply... At least, now I can change the chip without soldering.
Looks like I'm making a systematic error here. Please advise about a save way, to connect power and key, once the chip is programmed. It seems to me, that it only happens, once the chip programmed.
Thanks for the help,
EWo
Can you try the SX-Key on something else (like the SX Tech board) ?
You need to determine if the SX-Key is damaged. If it's not, then there is probably something wrong with your board.
You do have the 10K pullup on the /MCLR pin right...
I connect and disconnect the SX-Key pretty often. It's not a smart thing to do, but in all the times I've done it I've only ever had 1 SX-Key get damaged. Maybe you were just unlucky...
Bean.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Never argue with an idiot.· They'll drag you down to their level then beat you with experience.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
www.hittconsulting.com
·
The Key is OK, I tried on my SX28 Proto Board. That is the strange thing, on the Proto Board I never experienced any problems like this.before (and now...)
EWo
If you have these two things you should be golden. I usually put a 0.1uF cap right at the programming header too.
Bean.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Never argue with an idiot.· They'll drag you down to their level then beat you with experience.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
www.hittconsulting.com
·
I will go ahead and ad the 10K resistor. A cap is already in from the start. It is probalbly something, what should be mentioned in the manual. I'm a little disapointed, that I lost two chips because of a missing/wrong information in the manual... (see page 13)
I just hope, that UPS will hurry up, since I fried even my spare chip, I'm grounded for now...
Thanks again,
EWo
What you see in the picture is about the absolute minimum you need to connect the SX-28 chip. You can use a jumper to supply the power, and if you want a crystal, I made a little module that plugs into the place where the SX-Key goes so I can easily change between the two.
http://forums.parallax.com/showthread.php?p=659734
Hope it helps,
Dan
Post Edited (DosManDan) : 7/6/2007 6:05:49 PM GMT
I find it hard to believe that you toasted two chips just because you didn't use the resistor. I have connected /MCLR directly to +5 without damage.
Bean.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Never argue with an idiot.· They'll drag you down to their level then beat you with experience.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
www.hittconsulting.com
·
I put in the 10K between /MCLR and +5V and checked the whole board really through and throug.
No shorts or other bad connections to be found. Since I consider myself pretty experienced with that kind small boards (even if not with the SX) I'm sure: it's OK.
Then, just for the hack of it, I put in the chip again and connected the power. No abnormal heat so far. When I open the dialog for the device I can read and programm the device options. Ups... chip still alive???
I open my programm and want to download it... to bad: I get the message that the programming failed.
How sad, the chip seems not completely dad but is damaged.
The fact, that in both cases I were able to programm and run the chip, when it was "virgin" let me beleve, that the wiring were OK to begin with. Looks like the 10K made the diference.
Thank you all for your help,
EWo
Due to the fact, that it will (hopefully) be airborne weight and size are essential as well as·being inert against vibrations.
EWo
Post Edited (EWo_Ge) : 7/6/2007 10:05:27 PM GMT
I just got the new SX-28 chips from Parallax. In the meanwhile I had·the 10K resistor installed. NO OTHER CHANGES. The wiring around it were not touched since measuring and checking again showed all in the green.
With the 10K resistor: NO SMOKING CHIPS ANYMORE.
Thank you all for your help.
Good luck and don't forget your 10K's,
EWo