Your longest serial cable connection
LoopyByteloose
Posts: 12,537
Okay, I finally finished my DIY setup that allows me to program a Propeller by wire at a distance. It starts with an RS232 interface at the PC and switches to RS422
50 meters of CAT5 cable _____________ RS422 to ttl at the Propeller.
It works quite well for 50 meters, but the RS422 literature claims 4000 feet is quite possible at 115,200 baud. If you take a few RS422 trancievers and build a repeater station for less than $5USD, you might double that distance. More repeaters, and more distance.
What is the longest serial cable you have ever done? For me, the 50 meters is more than enough; so is the 115,200 baud --- but much more is possible.
And what did you find it useful for?
50 meters of CAT5 cable _____________ RS422 to ttl at the Propeller.
It works quite well for 50 meters, but the RS422 literature claims 4000 feet is quite possible at 115,200 baud. If you take a few RS422 trancievers and build a repeater station for less than $5USD, you might double that distance. More repeaters, and more distance.
What is the longest serial cable you have ever done? For me, the 50 meters is more than enough; so is the 115,200 baud --- but much more is possible.
And what did you find it useful for?
Comments
Funny story: The hardware guys decided they had to test their creation. So they rented a drum of a kilometer or so of telephone cable. You know, cable as thick as your wrist with 20 or 40 or whatever twisted pairs in it. Loop those back a few times and you can easily test your range limits. Their lab was one floor up in the building so they wheeled that huge drum into the lift to get it up there. For months after that the lift stopped short of each floor by one foot as they had seriously overloaded and stretched the lift cable.
Oh you mean from the Prop? About a meter:)
Had a gentleman call our tech shop a while back to ask how much faster a 50' serial cable would be over a 100' serial cable. The reply was "50' faster". The caller thanked us and hung up.
I have only located one USB to ttl breakout device that might do it. Sparkfun has one for $20 USD and it would require to use 3.3 ttl to RS422 chips or you have to hack the device to interface and provide power to +5V ttl.
I initally had a serious crosstalk problem with my simple DIY wiring of a MAX232 to sn75179 chips. Keep your Rx away from your Tx and Not parallel.
Do lift cables really stretch? I wonder as I always considered that the floor stop sensor was pulled out of alignment by an overload... maybe as a telltale warning to prevent repeated overloads.
Direct connection: PIC16F870>20 meters CAT5E UTP cable>PIC16F628A.
I've always felt that MAX232 and RS232 are a waste of time. Computer should have and RS422 full-duplex port.
I am actually using 3 twisted pairs to program the Propeller.
Try these USB-422 adapters from FTDI. I use them everywhere. The PCB w/o cable version is really handy because it has pads to solder your own cable onto and access the +5VDC.
http://www.ftdichip.com/Products/Cables/USBRS422.htm
I built a 6-wire setup that has the Reset that is need to program the Propeller from afar.... not just Rx and Tx. (Maybe Parallax will consider producing these long-distance programers).
One still has to build a special device at the Propeller end to provide the open-collector for Reset.
As it turns out, light travels about 1 foot in 1 nanosecond (in free space). So, you could have said 50 nanoseconds! The savings really add up.
Electrical signals in conductors are a bit slower so probably closer to 70 - 80 nanoseconds.
I had a roll of 1000ft (305 meters) of CAT5E cable lying next to my table, where two stamp boards were testing RS-422 connection. So I was curious, whenever it will work over such long cable. Used one pair - it worked, connected with another pair in series - works, connected with 3rd pair in series - hey, works again! I was not able to test 1200 meters (4nd pair) because this cable was missing it! this was factory run error leftower, so I bought it for very low price, don't remember exactly, around $15 I think.
I think it was something like 300 baud (might have been even slower)...
With the RS422, you don't have to slow down as much and all that electrical interference is nearly eliminated. I just wonder about lightning strikes with all that wire being put out and about.