ESP01 - Port Expander - ULN2003 step motor controller

ESPHome
1

Hi all,
In a ventilator project, I want to use a ULN2003 based step motor controller that is controlled by four input pins.

I would like to use an ESP01 with an MCP23017 port expander.

In the esphome configuration I have defined four expander outputs like this:

switch:
  - platform: gpio
    name: "ventCtl G0"
    pin:
      mcp23xxx: mcp23017_hub
      number: 0
      mode:
        output: true
      inverted: false
  - platform: gpio
    name: "ventCtl G1"
    pin:
   ...

…and in the stepper configuration I am using the expander references:

stepper:
  - platform: uln2003
    id: ventCtl_move_stepper
    pin_a: "ventCtl G0"
    pin_b: "ventCtl G1"
    pin_c: "ventCtl G2"
    pin_d: "ventCtl G3"
    max_speed: 250 steps/s

But validation fails:

INFO ESPHome 2024.9.2
INFO Reading configuration /config/esphome/vent-ctl.yaml...
Failed config

stepper.uln2003: [source /config/esphome/vent-ctl.yaml:76]
  platform: uln2003
  id: ventCtl_move_stepper
  
  Cannot resolve pin name 'ventCtl G0' for board esp01_1m.
  pin_a: ventCtl G0
  ...

So my questions are:

  • is it not possible to use port expander GPIO ports for the stepper component?
  • or can only native GPIO ports (like GPIO0 and GPIO2 for the ESP01). So that I will have to use another ESP familiy variant with more native GPIO ports?

I hope the above makes sense? :slight_smile:

2

While I’m not sure if you can make it work with Esp-01, at least you have to have I2C and mcp23017 components on your yaml.
My honest opinion is to use another Esp board with sufficient number of Gpios.

3

The immediate cause of the error is your failure to correctly specify the I/O pins for the stepper. You should not be defining those switches, just put the full pin schema in the stepper config, something like this:

mcp23017:
  id: mcp

stepper:
  - platform: uln2003
    id: ventCtl_move_stepper
    pin_a:
      mcp23xxx: mcp
      number: 0
    pin_b:
      mcp23xxx: mcp
      number: 1
    pin_c:
      mcp23xxx: mcp
      number: 2
    pin_d:
      mcp23xxx: mcp
      number: 3
    max_speed: 250 steps/s

While I would second the advice to use a better board for the task, it might just work with what you have though the max speed of 250 steps/s might not be achievable.

4

Hi Karosm,
Thank you for your reply. I do have I2C and mcp23017 components configured. But omitted them for brevity.
And I agree that using a more capable ESP board would make my day easier. But I am just interested to see if an ESP01 and a port expander could be used with the step motor :slight_smile:

5

Hi Clyde,
Thank you for your reply. Yes, this was exactly what I was looking for. And after modifying my stepper component pin configuration as per your example, controlling the step motor through home assistant worked like a charm :slight_smile: :+1:

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