Allow using shift register outputs for pin assignments

[cass3825]

Here's what I'm hoping to accomplish:

display:
- platform: 7segment_gpio
  id: lcd
  digit_pins: [G1,G2,G3,G4]
  iterate_digits: false
  segment_pins: [G,F,E,D,C,B,A,DP]

sn74hc595:
  - id: 'sn74hc595_hub'
    data_pin: GPIO20
    clock_pin: GPIO8
    latch_pin: GPIO19
    oe_pin: GPIO21
    sr_count: 3

output:
  - platform: gpio
    id: "A"
    pin:
      sn74hc595: sn74hc595_hub
      number: 0
      inverted: false

  - platform: gpio
    id: "B"
    pin:
      sn74hc595: sn74hc595_hub
      number: 1
      inverted: false

  - platform: gpio
    id: "C"
    pin:
      sn74hc595: sn74hc595_hub
      number: 2
      inverted: false

  - platform: gpio
    id: "D"
    pin:
      sn74hc595: sn74hc595_hub
      number: 3
      inverted: false

  - platform: gpio
    id: "E"
    pin:
      sn74hc595: sn74hc595_hub
      number: 4
      inverted: false

  - platform: gpio
    id: "F"
    pin:
      sn74hc595: sn74hc595_hub
      number: 5
      inverted: false

  - platform: gpio
    id: "G"
    pin:
      sn74hc595: sn74hc595_hub
      number: 6
      inverted: false

  - platform: gpio
    id: "DP"
    pin:
      sn74hc595: sn74hc595_hub
      number: 7
      inverted: false

  - platform: gpio
    id: "G1"
    pin:
      sn74hc595: sn74hc595_hub
      number: 8
      inverted: True

  - platform: gpio
    id: "G2"
    pin:
      sn74hc595: sn74hc595_hub
      number: 9
      inverted: True

  - platform: gpio
    id: "G3"
    pin:
      sn74hc595: sn74hc595_hub
      number: 10
      inverted: True

  - platform: gpio
    id: "G4"
    pin:
      sn74hc595: sn74hc595_hub
      number: 11
      inverted: True

[asergunov]

The main challenge I can see is we changing pins in timer ISR to handle correct "blinking". The sn74hc595 component pin writing doesn't have this code in ISR memory. Also we have to switch all them at once, not one by one as they do.

So we need to update sn74hc595 component with ISR safe functions to set all pins at once and use it in our code.

We can easily detect pin type in Python code.

[cass3825]

Thanks for the quick and thorough response! Regarding detecting pin type in Python code, what would you suggest modifying the cv.ensure_list(gpio_output_pin_schema) code to? What other Python code changes would you suggest to resolve the "Cannot resolve pin name" error when compiling?

As a "bandaid" to switching all of the inputs at once, I believe we can comment out the OE pin assignment in our use of the sn74hc595 component, then manipulate the pin within the display call. Thoughts?

[asergunov]

Regarding detecting pin type in Python code, what would you suggest modifying the cv.ensure_list(gpio_output_pin_schema) code to? What other Python code changes would you suggest to resolve the "Cannot resolve pin name" error when compiling?

This exactly the place where it makes sure you give it GPIO pin. sn74hc595 pins should fail this check by design.

If you change it to output_pin_schema the pins should match. So you can test on your hardware and maybe use. But I will not approve such PR. Maybe they have check for output irs-safe pin. This I will approve.

As a "bandaid" to switching all of the inputs at once, I believe we can comment out the OE pin assignment in our use of the sn74hc595 component, then manipulate the pin within the display call. Thoughts?

I'd extend output pin interface for latching. So we call latch for all the pins. It increases the counter in sn74hc595 component. We switch all the pins but that doesn't produce any signals. We call unlatch for all the pins. Counter goes to zero. Component switching all the pins with one command.