TI-H: Re: i2c interface


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TI-H: Re: i2c interface




I'm sending this design to the Ti-Hardware list, since some may find it
useful. I could modify it for output as well, allowing it to be used as a big
light flasher

Back in the early days of the ESF, before it even was working, mel Tsai made a
shift register to run normal memory. It stored some bits in the register and
used them as an address and then some more for data.

The simplest way is to have it send to a shift register or a counter. A step
counter might be better (simpler).

Send a single pulse to the counter to step between devices. then read the
input. if it's high, then it is closed, and low, it's open circuit.

You can use various circuits to decode the binary output. I can't think of any
right now, but a cheap 4 bit counter will do 16 devices!

The problem is if the counter is off some how, the computer may be a device
off, thinking say, sensor 2 was sensor 1. You just have to see what works.
you'll have to calibrate it to make sure the thing is timed right. It should
work fine though. only 1 send and one recieve line is needed and the only data
is a single pulse to step to the next sensor, and the read bit is either high
or low.

A Binary to bar graph driver is OK to convert from the counter to the sensor
select, but it has to be the single dot type, not a bar.

There are various circuits you can use, but this should be fairly simple. I
know what the stuff does, but not part numbers, so I can't give you a parts
list though, sorry!

Easier than I2C though!


              ~           ~
           ___|___     ___|___
_____\____| 4-bit |___|       |__S1__
     /    |Counter|___| 4-bit |__S2__|
          |       |___|16 dot |__S3__|
          |       |___| graph |__S4__|
          |_______|   |display|__S5__|
              |       |driver |__S6__|
             _|_      |       |__S7__|
              =       |       |__S8__|
                      |       |   :  :
                      |       |   :  :
                      |       |__S15_|
                      |       |__S16_|
                      |_______|      |
                         _|_         |
                          =          |
_____/_______________________________|
     \

Tx signal
Tx:0:1:0:1:0:1:0:1:0:.......:1: 0: 1: 0: 1: 0: 1:0:1:0:1:0:...
Sn:1:2:2:3:3:4:4:5:5:.......:14:14:15:15:16:16:1:1:2:2:3:3:...
Sensor number

Rx: sensor closed=1: sensor open=0

-- 


Richard Piotter
richfile@prairie.lakes.com

The Richfiles TI Hardware and BASIC web page:
http://www.geocities.com/SiliconValley/Lakes/5081/Richfiles.html


References: