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???
07/05/06 14:06
Modified:
  07/05/06 14:21

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#119677 - the reality is
Responding to: ???'s previous message
hi,

Abhishek Bk said:
But do you have an inexpensive 8051 based MCu that has 16 programmable input output lines?


Doing your way why not to switch to even smaler, let say, 8 IO lines MCU and place two ones for each relays` group? That was a kind of irony, sorry. The reality is that there is no reason for such occupation people see here. With ordinary MCU you need only 8+3 IO lines and a couple of simplest chips to do all the job.
From other side, if you do not look for simple way then maybe is it time to look at PLDs? Let say, Altera EPM7128STC100 for about 10USD.

As about 16 IO lines MCUs so most Atmel cheap derivatives (AT89C2051-like ones) have only 15 lines. But this is not a problem in the whole. There is magic word called "multiplexing". Use this way:
- 8 lines as inputs from relays;
- 3 lines for addressing slave MCUs from host to all slaves;
- 3 lines for addressing relays` contacts from host MCU to all slave MCUs;
- 1 back-loop data line hardwired from all slaves to host MCU.

Totally it requires 8+3+3+1=15 for slave MCUs; 3+3+1=7 for host MCU. But note that you should assign slave address for each slave during flashing them.

Another way:

- 8 lines as inputs from relays;
- 3 lines for addressing relays` contacts from host MCU to all slave MCUs;
- 8 back-loop data lines (one per slave) from slaves to host MCU.

Totally it requires 8+3+1=12 for slave MCUs; 3+8=11 for host MCU. Here all slaves will have the same software.

There are other configurations you may imagine then. Moreover using a word "protocol" and some software work you may decrease slave MCU even to 9-lines one, for example (the key: 1-wire communication).

Regards,
Oleg

List of 34 messages in thread
TopicAuthorDate
Debouncing with an 8051 of 16 I/O pins            01/01/70 00:00      
   You don't need these slave micros            01/01/70 00:00      
      yes, but some more questions            01/01/70 00:00      
         Not scary at all...            01/01/70 00:00      
            In that case.....            01/01/70 00:00      
            here is the schematic            01/01/70 00:00      
               I would try shift registers            01/01/70 00:00      
               just a note            01/01/70 00:00      
                  The joke is:            01/01/70 00:00      
                     the reality is            01/01/70 00:00      
                     Re: The joke is            01/01/70 00:00      
      correct, but            01/01/70 00:00      
         I was assuming...            01/01/70 00:00      
   Bounce time of your relays?            01/01/70 00:00      
      Not very clearly            01/01/70 00:00      
         Bravo!            01/01/70 00:00      
   The original question            01/01/70 00:00      
      What's wrong with the shift register sol            01/01/70 00:00      
      HUH?            01/01/70 00:00      
         I am sorry            01/01/70 00:00      
            that was not the issue            01/01/70 00:00      
   why oh why oh why oh why            01/01/70 00:00      
      because it cost nothing            01/01/70 00:00      
         yeah right            01/01/70 00:00      
            yes, they do            01/01/70 00:00      
            Design is a state function            01/01/70 00:00      
               All the more using shift registers!            01/01/70 00:00      
                  I think your solution is better            01/01/70 00:00      
                     I guessed so...            01/01/70 00:00      
                  hidden part            01/01/70 00:00      
                     I can see a 'lucky sample' of a shift re            01/01/70 00:00      
                     True, but...            01/01/70 00:00      
   jezwolds hardware switch debouncer            01/01/70 00:00      
   The facts about costs of Debouner chips            01/01/70 00:00      

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