Hello folks,
Again new project, so would like to know your opinion before PCB making.
Need to replace MCP23017 based IO board. Was good to lit led or receive push buttons. But not that handy for control cabinet, relay switching and mainly receiving signals from AC contactors.
In short, MCP is like an antenna! Here is my advise to go that way.
- place your MCP board as far as you can from any cable AC loaded
- make sure your DC supply negative pole is connected to AC grounding (green yellow).
- even surge suppressor addon on the contactors did stop MCP IC used as input failing operation,need to reset, sometimes software init enough, sometime power cycle needed...
- gonna try ferrite core beads on input lines and power lines, but no trus in that IC any more
As replacement, want to use shift registers, as it should be much more reliable in compare to I2C MCP antenna and also much cheaper these days. Few years ago MCP for 2.5$ and now even 20$/each. What a hell?
In my project I am limited to 10pin header interface, and I want to daisy chain as well. So count with me...
First two pins are power of course.
Third I want to use for 74HC595 OE' pin, as kind of hardware watchdog, to make sure outputs does not stay high in any case CPU is not in control...
4th is for 74HC595 Q' pin for daisy chaining
5th is for 74HC165 data daisy chaining pin
Here it comes, I have not 3 pins for each IC control.
Common CLOCK pin should be not an issue as long I will synchronise register read/write,right?
I suppose it should work, anyone tried?
But I was thinking even 4 should be enough, means common LATCH pin. As long as there is more output registers than input registers.
Thinking about the code is shouldn't have any big disadvantages, or is it?
Any experience sharing is appreciated!
Kind regard Mira