problem with synching 74hc165 and 74hc595

Other Hardware LEDs and Multiplexing
1

hi
im using two multiplexer IC's
74ch595: to increase digital output pins
74ch165: to increase digital input pins

I've used them separately,and now i want to merge them and make a PCB for further use

the problem is i want to synch them and i don't know if they have common pins,and if they have,which pins are they...

if there is an IC,doing both increasing digital I/O pins,pls mention that too

thank you so much

2

R0UGH:
im using two multiplexer IC's

Where? 74HC595 and 74HC165 are shift registers :wink:

Syncing them should not be to hard... Just latch them at the same time. You can even have them as a single daisychain if you want to :slight_smile:

3

Yes, they are shift registers, not multiplexers in the usual sense of the word, but you can use them to add extra input and output pins.

Connect SER on the 595 to MOSI on the Arduino. Connect QH on the 165 to MISO on the Arduino.

Connect SRCLK on the 595 and SCK on the 165 to SCK on the Arduino, RCLK on the 595 and SH on the 165 to SS on the Arduino.

Don't forget the 0.1uF bypass caps on each chip.

4

There are many chips that can increase digital I/o, such as mcp2308, mcp23017, mcp23s08, mcp23s17, pcf8574, pcf8575.

5

And many more specialized chips. For adding PWM channels, driving LED displays, reading keyboards...

6

septillion:
Syncing them should not be to hard... Just latch them at the same time. You can even have them as a single daisychain if you want to :slight_smile:

You probably do not want to latch both at the same time as you do not necessarily want to update the output register every time you read the input register, and you have to shift out the output data before you latch while you have to shift in the input data after you latch it. :grinning:

7

I agree, but that does make them out of sync :stuck_out_tongue: Aka, it's up to the OP what he really wants :slight_smile:

8

PaulRB:
Yes, they are shift registers, not multiplexers in the usual sense of the word, but you can use them to add extra input and output pins.

Connect SER on the 595 to MOSI on the Arduino. Connect QH on the 165 to MISO on the Arduino.

Connect SRCLK on the 595 and SCK on the 165 to SCK on the Arduino, RCLK on the 595 and SH on the 165 to SS on the Arduino.

Don't forget the 0.1uF bypass caps on each chip.

thanks a lot man
I've found schematics on the internet,but there was no capacitors in any of em to bypass anything!
will you explain a lil more pls?! :slight_smile:

9

PaulRB:
There are many chips that can increase digital I/o, such as mcp2308, mcp23017, mcp23s08, mcp23s17, pcf8574, pcf8575.

do any of these chips do increasing both input and output digital pins at the same time?!

what about analog pins,can i expand em with any specific chip?!

10

do any of these chips do increasing both input and output digital pins at the same time?!

Yes they all do. You have a choice of what pins are defined as inputs and what as outputs, just like the pins on the Arduino.

I've found schematics on the internet,but there was no capacitors in any of em to bypass anything!

Shows you how crap the circuit is then, treat it with caution.

will you explain a lil more pls

Explanation here:- http://www.thebox.myzen.co.uk/Tutorial/De-coupling.html

what about analog pins,can i expand em with any specific chip

Yes search for an "analogue multiplexer" chip. Like the CD4052.

11

Grumpy_Mike:
Yes search for an "analogue multiplexer" chip. Like the CD4052.

Or the enhanced performance version, the 74HC4052.

(The relatively obsolete CD4052 operates over a wider voltage range, but since the Arduino ADC does not, that is moot. :astonished: )