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???
05/02/09 12:23
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 		 #165004 - I had done something like this in past
Responding to: ???'s previous message
Dear Giang,

In past, I had similar task of displaying same data on two LCDs (4x20).

The difference between my requirement & yours are...
1> I was needing only about 10 feets of distance.
2> Environment in which it is used is very stable.
3> Board 'B' the intermideate one was not needed for me.
4> Ofcourse there was a time lag if entire display with non constant data is to be changed. But it was not significant (only max of 1sec)

The scheme I used is ...
1> The main board MCU communicates to slave MCU on another board using I2C.
2> As both firmwares are designed by me; I designed few custom protocols(e.g. first two char after slave address denotes protocols e.g. 0x0000 means clear Slave LCD. 0x0001 means display following data on line 1, etc...)
3> pattern was slave address, protocol, parameter if any (e.g. string to be displayed for protocol = 0x0001), then a chksum, and stop bit of I2C.
4> Slave asks for retransmission if chksum mismatch. Also main MCU can poll wheather slave is free to recieve next data.

Well this is not the only way. Also I2C at 10 feets subjects to surrounding conditions. But you can check if you can get some idea from it.


Regards,
Mahesh

List of 24 messages in thread
TopicAuthorDate
How to read and redisplay from LCD databus?            01/01/70 00:00      
   Spy on the Data & Control lines            01/01/70 00:00      
      Can be hard to be fast enough            01/01/70 00:00      
   Shouldn't be a problem            01/01/70 00:00      
      some HW might be needed            01/01/70 00:00      
         Monitor the LCD databus then send via 485            01/01/70 00:00      
         I don't see a place for the 805x            01/01/70 00:00      
      Re: Shouldn't be a problem            01/01/70 00:00      
         some basic questions            01/01/70 00:00      
            Re:some basic questions            01/01/70 00:00      
               20 Meters            01/01/70 00:00      
                  Re: 20 Meters            01/01/70 00:00      
      Signal timing and command timing separate issues            01/01/70 00:00      
         Check the datasheet ...            01/01/70 00:00      
            Re: Check the datasheet ... and test on LCD of board B first            01/01/70 00:00      
               A CPLD at each end would do nicely            01/01/70 00:00      
                  Re: A CPLD at each end would do nicely            01/01/70 00:00      
                     it depends on requirements            01/01/70 00:00      
                        Watch out for assumptions about busy            01/01/70 00:00      
                           If that gets to be an issue ...            01/01/70 00:00      
                              slave timing            01/01/70 00:00      
                                 I doubt that will work.            01/01/70 00:00      
   I had done something like this in past            01/01/70 00:00      
      Re: I had done something like this in past            01/01/70 00:00      

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