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emavil
Joined: 18 Oct 2005
Posts: 53
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 26 May 2008 8:26 Communicating to other uC at a distance of 100m or more |
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| Hi guys, I am working with two microcontroller projects that communicates using SPI wherein both of them are 100meters apart. Is there any least possible electronic solution to this?
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tvthang
Joined: 17 May 2008
Posts: 46
Helped: 5
Location: Ho Chi Minh city, VietNam
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26 May 2008 9:01 Re: Communicating to other uC at a distance of 100m or more |
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| Hi, to communicate between 2 uC, you should use UART, you use 2 MAX485 to exchange from TTL to RS485, in which distance may be 2km.
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sohailkhanonline
Joined: 08 Oct 2007
Posts: 33
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26 May 2008 9:46 Re: Communicating to other uC at a distance of 100m or more |
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| Above solution is working. I have implemented it
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randell_xtian
Joined: 25 Mar 2008
Posts: 158
Helped: 9
Location: Philippines
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26 May 2008 10:38 Re: Communicating to other uC at a distance of 100m or more |
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i suggest that you may used a RF IC/RF module for wireless communication. 
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FvM
Joined: 22 Jan 2008
Posts: 5154
Helped: 766
Location: Bochum, Germany
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26 May 2008 10:40 Re: Communicating to other uC at a distance of 100m or more |
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| If - for any reason - a SPI interface has to be extended to 100 m, then this can be done using multiple differential pairs and RS422 respectively RS485 driver/receiver. You should consider, however, the roundtrip cable delay of about 1 us.
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Sayem Ahmed
Joined: 07 Apr 2008
Posts: 47
Helped: 3
Location: Dhaka,Bangladesh
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26 May 2008 13:26 Re: Communicating to other uC at a distance of 100m or more |
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One quetion freinds
when i am using a mcu with usart like 16f877 and only want to send data then should i have to use max233 or any of them for distant transmition.
Thanks.
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emavil
Joined: 18 Oct 2005
Posts: 53
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27 May 2008 9:39 Re: Communicating to other uC at a distance of 100m or more |
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thanks to all who responded. I am not familiar with RS485, currently i'm using buffer ICs like 74LS244 at the transmitter module and another 74LS244 at the receiver module. I am transmitting digital singals at TTL levels for SPI (Strobe, Data, Clock) using ordinary telephone cord. One line of the telephone cord is used to connect Grounds of the both modules. It worked. I also tried using UTP cable(Unshielded Twisted Pair) and it worked also for about 15 meters.
I would like to ask for technical support regarding the method that i'm using. What will happen to this configuration if i go for 50m or more?
Will my configuration affected with this "Ground Loop"?
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FvM
Joined: 22 Jan 2008
Posts: 5154
Helped: 766
Location: Bochum, Germany
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27 May 2008 9:51 Re: Communicating to other uC at a distance of 100m or more |
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| Industrial RS485 networks are mostly using opto-isolated RS485 to achieve reliable operation also if ground voltage differences are present. It depends on your electrical enviroment, if RS85 is operational without isolation, probably yes. But you should activate potential interference sources for test, e. g. switch fluorescent lamps or electrical machines.
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b.zahedi
Joined: 20 May 2008
Posts: 18
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27 May 2008 11:54 Communicating to other uC at a distance of 100m or more |
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| max485 is very simple, for reliable communication you'd better use one in the transmitter side and another in the receiver side
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FvM
Joined: 22 Jan 2008
Posts: 5154
Helped: 766
Location: Bochum, Germany
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27 May 2008 12:32 Re: Communicating to other uC at a distance of 100m or more |
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| I agrre with b.zahedi. I didn't read from your post (or couldn't believe) that you wanted to continue using single-ended TTL signals for distant communication, but I fear, he understood it correct.
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