New computer, no RS-232 for SX-Key
KenBash
Posts: 68
I had to purchase a new laptop recently,· I got a really nice HP with all the bells and whistles.... except when I went to work on an SX-48 project and went to plug in the RS-232 cable for the SX-KEY...· NO BELL.... NO WHISTLE.· I hadn't even thought to check for an RS-232 port when I purchased it.
I bought a couple of different USB to RS-232 converters, but they don't work with the SX-Key.
The HP docking station doesn't even have RS-232!
I am considering purchasing a third party docking station that does have RS-232 but I have difficulty with purchasing a $200.00 device with no certianty that it will work.
questions:·
·· 1. Is there any way to make an SX-Key work with a USB port?
···2. if not, are there any other ways to bring SX development to the newer laptops·without an RS-232 port?
·I have several SX-keys, I don't mind sacrificing one. ( cut, patch, hack, whatever).
·A new SX-Key that works from·a USB port would be better.
Any solution would be greatly appreciated!
Ken Bash
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" Anything worth doing... is worth overdoing. "
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I bought a couple of different USB to RS-232 converters, but they don't work with the SX-Key.
The HP docking station doesn't even have RS-232!
I am considering purchasing a third party docking station that does have RS-232 but I have difficulty with purchasing a $200.00 device with no certianty that it will work.
questions:·
·· 1. Is there any way to make an SX-Key work with a USB port?
···2. if not, are there any other ways to bring SX development to the newer laptops·without an RS-232 port?
·I have several SX-keys, I don't mind sacrificing one. ( cut, patch, hack, whatever).
·A new SX-Key that works from·a USB port would be better.
Any solution would be greatly appreciated!
Ken Bash
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" Anything worth doing... is worth overdoing. "
··············································· ( R.A.H. )
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Comments
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"If you want more fiber, eat the package.· Not enough?· Eat the manual."········
·· Not everyone...·
http://www.parallax.com/detail.asp?product_id=800-00030
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Chris Savage
Parallax Tech Support
csavage@parallax.com
I have the same problem with my notebooks. I tried a belkin USB to serial adapter, but no dice.
So I bought the one from Parallax and it works fine.
Bean.
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Cheap 4-digit LED display with driver IC·www.hc4led.com
Low power SD Data Logger www.sddatalogger.com
"I'm a man, but I can change, if I have to, I guess" The Red Green Show
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I really thought everyone was off. Don't work to hard.
Bean,
From what I recall, several of these USB to serial adapters do not provide all the connections needed to use the SX-Key. Correct me if this is wrong.
1. The chip provides all the signals needed
2. The software drivers are NOT a problem as Parallax provides those for their adapter
3. The USB port can support RS-232
4. The problem lies in several manufactures preferring not to connect handshaking and control lines on the RS-232 side. [noparse][[/noparse]I suppose to reduce production costs].
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"If you want more fiber, eat the package.· Not enough?· Eat the manual."········
Hope you're out enjoying the fireworks somewhere and not reading this! LOL
Ken
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" Anything worth doing... is worth overdoing. "
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·· My family is on the other side of the country for the summer, so I'm trying to keep busy.
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Chris Savage
Parallax Tech Support
csavage@parallax.com
for the SX-Key, no handshake lines are required, just RxD, TxD, and Signal Ground.
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Greetings from Germany,
G
My recollections seem to be based on using the USB to Serial Adapter or USB2SER for the BasicStamps and the Propeller which require the DTR line. I didn't realize that the SX-Key doesn't have hardware handshaking. It seems important that the user buys the Parallax adapter as it supports all of these products.
Since none of the items on my list are involved, I still wonder where the problem lies.
There has been a lot of discussion that laptop serial ports do not provide a high enough voltage swings for the RS-232 standard. Could it be that most of these converters are no better? After all they are relying on the USB line for +5volts.
In other words, does anyone know what are the true RS-232 thresholds for the SX-Key?
If you are trying to use another RS-232 interface, that seems to be a useful piece of trouble shooting information for all.
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"If you want more fiber, eat the package.· Not enough?· Eat the manual."········
I would really like to know if I can just hook up the TX and RX lines, and have my sx key still work. If so, I will desolder the rs-232 plug, and replace it with fiber. Also, it would help to know the voltage swing VPP width.. Normal rs-232 can swing from -15v to +15v. What does the sx-key do?
Would like to know more.
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Meh. Nothing here, move along.
I couldn't locate a schematic either. I suspect that you need to insert a MAX-232 to get proper TTL with a good RS-232 interface. I would keep the SX-key intact and just build a converter as you need to provide outside power.
The basics are that RS-232 is NOT TTL; it should have a positive and a negative voltage of about 9 volts (but many manufacturers have been lax in providing those voltages as they require more parts); and also the RS-232 signals are inverted from the TTL. So a TTL high would be a -9Volts.
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"If you want more fiber, eat the package.· Not enough?· Eat the manual."········
To be honest I want to interface my sx-key ttl only, so that would mean getting a schematic. I don't see why would be such a big deal, as I would need the sx-key code to even replacate a sx-key. As a matter a fact, I don't even want the schematic.
If parallax would just tell me where I can send the RX and TX ttl level signals into, then I would do that. I don't want to mess around with rs-232 levels, and the chip / caps associated with it. Its a waste of space, the reason I like the sx-key is its size.
For some reason i feel that i just may have to go scope on this one. Its eaiser to have parallax tell me, but if the schematic for the sx-key isn't currently available, I doubt they will tell me how I can do this. So if anyone has any tips to save me some time, that would be great.
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Meh. Nothing here, move along.
There is a coil and some circuity set up to provide the higher voltage for the Osc pins to enter programing mode. Possibly they provided the higher RS-232 via their own power supply adaptation.
This seems to be geting off track. Mainly I wanted to clarify the V+ and V- threshold because the RS-232 standard has been compromised on many newer devices. The Forum gets a lot of postings from users that have problems starting out. Usually, it is a laptop or a USB port that is involved. Many have wasted money by buying a locally available product and found they still don't have what they need.
BTW, One other user had his SX-Key on a 25 or 50 cable. It is hard to believe, but it seems that whatever is driving the RS-232 is putting out good quality signals. I have no idea why he needed such a cable on the SX-Key, but it seems you have a similar need.
You could simply use that and forget the fiber optics. It certainly would be better to scope the RS-232 signal than to try to cut into an surface mount IC that is the size of a house fly.
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"If you want more fiber, eat the package.· Not enough?· Eat the manual."········
no more guesswork...
Please find attached a schematic showing the SX-Key serial interface circuitry. This is a really tricky way to interface to an RS-232 port, and it only works when only one device is sending data at a time (which is the case with the SX-Key).
The Schematic also shows that it is pretty simple to interface to TTL level: Simply connect the RxD line to X1, pin 2, and the TxD line to X1, pin 3. X1, pin 2 will be driven to +5V when the TX line is low, and pulled to low through R1+R2 when the TX line is high. When the SX-Key Transmitter is idle, TX is high, so a high or low TTL signal on X1, pin 3 will drive RX high or low through R1+R3.
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Greetings from Germany,
G
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Meh. Nothing here, move along.
this schematic shows the circuitry inside the SX-Key, so don't build it. In the meantime, the serial SX-Key has been replaced by the new SX-Key USB, so there is no more need for USB to Serial adapters here.
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Greetings from Germany,
G
Sooo.... Just getting tired of all the static and stuff with serial. Ground loops thru computers that have not so good power supplys, etc...
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Meh. Nothing here, move along.
this sounds promising, so why don't you build your own USB-Serial adapter. Knowing the Serial SX-Key input circuitry, you may notice that there is no need for shifting the FTDI chip's signals to +/- 12V.
Regarding ground loops, I absolutely agree with you, as I made my special experience yesterday. On a new SX-based board with an SX-Key USB attached to the usual 4-pin header, I tried to un-solder a capacitor I had added for testing before to a +24 V power line. Unfortunately, my soldering iron was grounded, my PC as well, and the board was still powered when I started this operation.
When I touched the cap's lead with the solder tip, I saw a little spark, and noticed that my 24 V, 8 Amp power supply had switched to fold-back mode, but only after sending at least 8 Amps through the SX-Key USB to the PC to ground to my soldering iron to the cap, etc....
When restoring power, my SX-Key USB got really hot, Totally frustrated, I turned off the whole setup, marked the SX-Key USB as "fried", and had a beer (or two).
Guess what - when I started my work on the setup again today, everything worked as usual, including the "fried" SX-Key. I'm not sure if it has seven lives - at least, it has two
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Greetings from Germany,
G
I had planned to turn the sx-key into optical. then from optical to usb serial ftdi.
With the sx-key I can do this. But the sxusb version i cannot.
(unless i was able to find a optical transmitter/receiver combo that is fast enough to pass the OSC1 and OSC2 data to and from the sx key.
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Meh. Nothing here, move along.
Then I can actually keep the serial stuff in place, power the sx-key with the serial line (regulated) and optically isolate my sx and my sx-key.
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Meh. Nothing here, move along.
Post Edited (BPM) : 7/29/2008 10:20:44 PM GMT
sorry to say that isolating OSC1/2 with optos won't work. Why? Well, the SX-Key uses OSC1 for clocking the target SX but also for feeding the +12V programming voltage Vpp into the chip. In addition, OSC2 is used for serial communication between the SX-Key and the target SX, and it is bi-directional.
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Greetings from Germany,
G