Arduino and 74x595

[Joseph Bento]

Thanks, Terry

It's time to heat up the soldering iron and give a couple of these 
circuits a try.  I've recently discovered tronixstuff.com where I now 
see there is a wealth of info for the 595 and the I2C chips that you 
mention.  I think it's time to finally get myself out of the strictly 
analog world of electronics I've been in for so many years.  :-)

Joe, N6DGY


On 3/30/2014 4:00 PM, wb4jfi at knology.net wrote:
> I don’t have a sketch, but I would say that you want to toggle the 
> clock line as many times as you want, in this case probably 32 times.  
> Keep the data line low except for the equivalent bit that you want to 
> turn on, and keep the latch line disabled until all 32 bits are 
> shifted into position.  Then toggle the latch bit once (up then down). 
> Both clock and latch lines are leading edge.  If that makes sense?  
> I’m sure a Google search will also help, as the 595 is a common way to 
> expand data I/O on the Arduinos.
> Another option that only requires two lines, but does require slightly 
> more expensive parts, would be to use I2C port extender ICs.  The 
> PCF8574P is a very popular 8-bit extender, while the PCA9555N handles 
> 16-bits of I/O.  Two PCA9555 (or equiv.) would do the same job.  There 
> are many others as well.  The Arduino Two-Wire library makes using I2C 
> devices very simple.  I’ve also use I2C 16x2 LCD displays, as that 
> also greatly reduces the number of pins used for these displays.
> I use these I2C chips all the time, as they don’t use up the limited 
> digital I/O pins of the Arduino.  For example, on a current project I 
> am using a PCF8574P for I/O expansion, a “digital pot” IC to control 
> the output level of the AD9850 DDS, an EEPROM (24LC256?) for a large 
> look-up table, a DS1307 RTC chip (for battery-backed-up RAM), and a 
> temperature chip, all using only the two I2C pins of the Arduino Uno.
> I2C, it’s a great tool!
> 73, Terry, WB4JFI
>

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