I2c, spi, rs232? Remote I/O - the 'best' way to go?
pacman
Posts: 327
I have a need to mount some remote I/O (for a single 7 segment 5" led display) some 4-5 meters (14-20 feet) away from my the Propeller controller.
The display needs to be powered from 12VDC (so the 'remote' board will likely have some passive components on it). Nothing flash, and not very fast update times (the number is likely to be changing in the vicinity of every 2-3 seconds.
Currently, the display is driven from a local relay board driving each segment individually. Not elegant, prone to wiring errors (it gets dis-assembled and trucked to a new location every couple of weeks).
I'm thinking some form of SIMPLE serial bus, but most of the data I have been able to source implies that I'm way out of 'length'. I could use something like 'standard serial' but then the remote board would need to have some clever decoding software on it as well as a RS232/485 interface.
As always I'm after a solution that doesn't cost the earth....
Can some of you suggest some options? (CANbus, ProfiBus with a twist of Lemon, Extra special super long - but low speed robust bus..., ??)
and if you know of a supplier for a Single 4" or 5" display (with appropriate 'driving' hardware to allow 'direct connection' to 12V that uses .... bus) then feel free to pass on that link
{i have searched, but no-one seems to do what I need, perhaps you know of "back-yard supplier J28 who does exactly what you need".}
Thanks heaps in advance...
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=================
The future is in our hands.
Which way to the future?
=================
Post Edited (pacman) : 10/12/2009 9:45:58 AM GMT
The display needs to be powered from 12VDC (so the 'remote' board will likely have some passive components on it). Nothing flash, and not very fast update times (the number is likely to be changing in the vicinity of every 2-3 seconds.
Currently, the display is driven from a local relay board driving each segment individually. Not elegant, prone to wiring errors (it gets dis-assembled and trucked to a new location every couple of weeks).
I'm thinking some form of SIMPLE serial bus, but most of the data I have been able to source implies that I'm way out of 'length'. I could use something like 'standard serial' but then the remote board would need to have some clever decoding software on it as well as a RS232/485 interface.
As always I'm after a solution that doesn't cost the earth....
Can some of you suggest some options? (CANbus, ProfiBus with a twist of Lemon, Extra special super long - but low speed robust bus..., ??)
and if you know of a supplier for a Single 4" or 5" display (with appropriate 'driving' hardware to allow 'direct connection' to 12V that uses .... bus) then feel free to pass on that link
{i have searched, but no-one seems to do what I need, perhaps you know of "back-yard supplier J28 who does exactly what you need".}
Thanks heaps in advance...
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
=================
The future is in our hands.
Which way to the future?
=================
Post Edited (pacman) : 10/12/2009 9:45:58 AM GMT
Comments
I'd use a 74HC595 for that purpose. It's an 8 bit shift register with an additional 8 bit output register. You can shift out your data bit by bit and when you're done activate the register clock to transfer the contents of the shift register to the output register all at once. You can also cascade as many HC595s as you like and still only need 3 pins. This could be reduced to 2 pins with an additional one-shot timer that pulls the register clock when there are no more shift clocks for a given time.
Cheers
Leon
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Cheers!
paul rowntree