Build Your Own SX-28 ISP/Debug Adapter
Guenther Daubach
Posts: 1,321
Hi Folks,
today, I found the need to debug an SX-28 on a PCB where I did not provide the usual 4-pin header for the SX-Key, and the OSC1 jumper because I never expected that it would be necessary to debug this “bullet-proof” application, but to be honest, the main reason for not providing the ISP feature was due to RFI and EMC reasons.
Nevertheless, I found a "quick-and-dirty" solution that I'd like to share with you.
The attached picture shall give you an idea. For further details, have a look at the attached PDF file.
Greetings,
G
today, I found the need to debug an SX-28 on a PCB where I did not provide the usual 4-pin header for the SX-Key, and the OSC1 jumper because I never expected that it would be necessary to debug this “bullet-proof” application, but to be honest, the main reason for not providing the ISP feature was due to RFI and EMC reasons.
Nevertheless, I found a "quick-and-dirty" solution that I'd like to share with you.
The attached picture shall give you an idea. For further details, have a look at the attached PDF file.
Greetings,
G
526 x 344 - 42K
Comments
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James Newton, Host of SXList.com
james@sxlist.com 1-619-652-0593 fax:1-208-279-8767
SX FAQ / Code / Tutorials / Documentation:
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(B#LL S*&T !)
This is my method of debugging after construction.
And just for reference, also is a pic of my "mad science" and yes, that is Mickey Mouse wallpaper.......my kids sleep in the back yard.......got to have your priorities set, right?
Ken
Post Edited (KenM) : 8/12/2004 3:40:53 AM GMT
Ken
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James Newton, Host of SXList.com
james@sxlist.com 1-619-652-0593 fax:1-208-279-8767
SX FAQ / Code / Tutorials / Documentation:
http://www.sxlist.com Pick faster!
Typically I will either single step through debug, or only reprogram via the ratsnest of wires and as of yet, no trouble
......funny thing too.....Some time ago, using the standard cable and SXTech board from Parallax, I often could not single step all the way through a program without the program·jumping to "nowhere land" at random locations in the debub process.
Between then and now the only thing that has changed is the date. I don't seem to have that problem anymore.....Solar flares?· heck I don't know.
Ken
My experience with the SX-Key is that it works fine programming an SX chip with the crystal/resonator·connected to the OSC pins but that strange things happen when it comes to debugging while the OSC1 pin still sees the crystal/resonator.
Another point is that an SX clocked @ 50 MHz nicely produces RFI at 50, 100, 150 MHz, and even higher. Long leads attached to the clock pins of the chip work as very efficient antennas which might make people happy listening to FM radio, or air liner pilots :-).
Greetings,
Günther
I don't have acces to a spectrum analyzer, nor are any of my project commercially sold. But I believe your products Guenther, are commercially sold, correct?
I know board layout and other factors contribute to the RFI, but at what frequency is typically the highest amplitude? Not having much experience in this area, I would assume the fundamental of 50 MHz produces the highest RFI.....or is it a different order?
Just curious.
Also, in the picture of the debugging cluge, did you notice the book lying on the table? If not, take a closer look. Thanks for all your support!
Ken
as far as I found out, RFI, or EMI issues come close to reading a crystal ball. I'm not an expert in this area either but as my SX stuff is actually commercially sold, I had to make some experiences, especially in the past few months where I spent several days in an EMC lab. I think this topic is worth a separate thread, and I hope that some real experts will drop in.·I'm going to put together some of the information, and experiences I could gather on that topic, and will post it unter a new thread soon.
For now, I only like to disclose that (as far as I found out) the fundamental is not this critical at all - the second harmonic is a killer, and the third can be even worse, and even at 450 MHz you can produce peaks that come close to 30 dBµV/m when you design your SX board the right way·
So stay tuned - I'll also include some·of the scans I have made because I think they they might be interesting to the SX community.
Hey - of course did I notice the book - you are a lucky guy, and already have a copy.·Mine did not yet arrive here but I recently tracked UPS, so I expect them to be delivered·by next·Monday.
Günther
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