Wemos S2 Mini: USB-C D+/D- (GPIO19/20) UART Fails for Novoferm

[petermdevries]

Feedback

The current documentation outlines a Wemos S2 Mini setup that taps into the USB-C connector's D+ (GPIO20) and D- (GPIO19) pins for UART communication.

Despite extensive attempts, this configuration fails to function as described, perhaps due to undocumented specifics. See also a Home Assistant community thread on the Novoferm 563S cover integration. (https://community.home-assistant.io/t/novoferm-563s-with-cover-component-not-working/903570)

Switching to alternative pins like GPIO2 and GPIO3 resolves the issue.

Users who have successfully used the USB-C method for a compact setup are encouraged to share their full YAML configurations and any extra settings. @ti-mo, could you confirm or provide details from your work in esphome/esphome#5933?

Otherwise make a remark on this in the documentation?

URL

https://esphome.io/components/cover/tormatic/

Additional information

No response

[ti-mo]

Aha! Someone else ran into this problem. 🙂 Well, I first started working on this component over the course of 2023, when remapping D+ and D- (still) worked without issues on my Wemos S2. Only a few months later, some esphome platform changes were made that broke this for some reason, so I never upgraded my ESP since I rely on the thing working as-is and the dongle was already made and installed.

I was going to bisect which change broke this, but it took literal years for the module to get merged, so that never happened.

For reference, my ESP is running 2023.11.6 (Dec 19 2023, 21:10:08), with literally nothing special for config:

esphome:
  name: novoferm

esp32:
  # Wemos S2 Mini
  board: lolin_s2_mini
  framework:
    type: esp-idf

uart:
  rx_pin: GPIO19
  tx_pin: GPIO20
  baud_rate: 9600

I remember using the arduino framework at the very beginning, but then I had to specify a few env vars to enable rebinding GPIO19/20. esp-idf worked better in general. I think this broke in 2024.1 or 2024.2.

[petermdevries]

Thanks for the info.

I've been testing to find out which version of ESPHome caused this issue. It works correctly up to and including version 2024.4.2, but starting from 2024.5.0, it no longer works.

I asked Copilot to check which change in version 2024.5.0 could be responsible, and it suggested the following explanation:

GPIO19 and GPIO20 are the USB D– and D+ pins on the ESP32-S2. On the Lolin S2 Mini, these pins are internally connected to the USB interface.

In ESPHome 2024.5.0, the recommended ESP-IDF version was bumped to 4.4.7 (see [esphome#6703]), and PlatformIO was also updated to 6.1.15.
These updates caused the Arduino framework (or ESP-IDF) to claim the USB pins more strictly during startup, meaning GPIO19/20 are no longer available for UART.

The best solution is to use different GPIOs. However, if you still want to use GPIO19 and GPIO20, you can completely disable USB with the following configuration:

esp32:
  board: lolin_s2_mini
  framework:
    type: esp-idf
    sdkconfig_options:
      CONFIG_USB_OTG_SUPPORTED: "n"
      CONFIG_TINYUSB: "n"

I can confirm that this works. I’m now running ESPHome 2025.10.3, successfully using GPIO19/GPIO20 via the USB-C connector.