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???
02/13/06 19:33
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 		 #109880 - No illnes seen until today
Responding to: ???'s previous message
Erik Malund said:
bit-bang which is 1% of processing total is still 100% of processing when it takes place. If you can accept 100% at such times, who cares, if you can't then you need HW IIC.


A single byte on SW-I2C cost only 100% for 100µs of the main loop time.
Since typically a main loop must be fast from the humans view, no human was able to detect a 100µs delay.

You can also often see a HD44780 LCD connected over PCF8574 and SW-I2C without noticeable slowing down the whole program from the humans view, e.g. pressing a key was displayed instantly.

Erik Malund said:

So, Peter, in many cases you can use bit-bang with no ill effect, but, as I post, not in all. Should that be a reason to shun HW IIC? that is where we disagree.



Please can you explain what do you mean with "ill effects" ?

SW-I2C need no interrupts and need also no interrupts to be disabled. So all fast things are fully unaffected by SW-I2C.
And again, I know no main loop which can not tolerate several 100µs delay.

On my experience a HW-I2C was only really needed in very rarely cases or to support I2C slave or multimaster.


Peter



List of 35 messages in thread
TopicAuthorDate
I2C bit banging            01/01/70 00:00      
   It has I2C bus            01/01/70 00:00      
      question, language and added info            01/01/70 00:00      
         SMB more reliable?            01/01/70 00:00      
            I never hung            01/01/70 00:00      
               Hanging I2C            01/01/70 00:00      
                  No LCD drivers, no hotplug            01/01/70 00:00      
                  Hanging I2C, and freeing it again            01/01/70 00:00      
                     Me too!            01/01/70 00:00      
                        which confirm            01/01/70 00:00      
                           So you've never had to            01/01/70 00:00      
                              I tend to fix hardware shortcomings with            01/01/70 00:00      
                                 Like I said, lucky.            01/01/70 00:00      
                                    doing the impossible            01/01/70 00:00      
                                       Even a nice word for it!            01/01/70 00:00      
                              Look at the philips I2C bus muxes            01/01/70 00:00      
                                 That would make sense            01/01/70 00:00      
            No            01/01/70 00:00      
               For hot plug use SMB            01/01/70 00:00      
               differences SMB IIC            01/01/70 00:00      
   I2C with hang recovery            01/01/70 00:00      
    I2C bit banging: yes !            01/01/70 00:00      
      I see nobody "fighting"            01/01/70 00:00      
         Re Erik            01/01/70 00:00      
            WHO, in his/her right mind would use pol            01/01/70 00:00      
               Really ?            01/01/70 00:00      
                  never used the 552            01/01/70 00:00      
                     HW-I2C not identical !            01/01/70 00:00      
                        where did you gtet that impression?            01/01/70 00:00      
                           Nice            01/01/70 00:00      
                           Re: SW-I2C efficiency            01/01/70 00:00      
                              then the question is "when"            01/01/70 00:00      
                                 No illnes seen until today            01/01/70 00:00      
                                    well, I can't            01/01/70 00:00      
            Good point            01/01/70 00:00      

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