I should also note that with this configuration, esphome successfully flashes and connects to Wi-Fi as though everything is great. When I update the state of the On/Off or Swing register however, it says that no modbus response is received.

Hi there -

I'm looking to flash my T-RSC3 with esphome and use the RS485 interface to expose sensors to my home assistant installation.

I currently have my RS485 A/B buses wired up to my modbus device (which is device 0x1). From what I understand RS485 TX is GPIO10 and RX is GPIO03.

So far I'm not getting any proper 2-way communication with the modbus device (including when I've tried swapping the A/B wires just in case). This is my esphome configuration, could you please confirm that the pins and settings look correct as far as you can see? I will also be following up on the esphome support for support on the software side. I can confirm that with similar settings on a USB RS485 adapter, I am able to communicate with the modbus device however.

esphome:
  name: hvac-01
  friendly_name: hvac-01

esp32:
  board: esp32-c3-devkitm-1
  variant: esp32c3
  framework:
    type: arduino

# Enable logging
logger:

# Enable Home Assistant API
api:
  encryption:
    key: "REDACTED"

ota:
  password: "REDACTED"

wifi:
  ssid: !secret wifi_ssid
  password: !secret wifi_password

  # Enable fallback hotspot (captive portal) in case wifi connection fails
  ap:
    ssid: "Hvac-01 Fallback Hotspot"
    password: "REDACTED"

captive_portal:

#========================

uart:
  id: modbus_uart1
  tx_pin: GPIO10
  rx_pin: GPIO03
  baud_rate: 9600
  stop_bits: 1
  parity: NONE

modbus:
  id: modbus1
  uart_id: modbus_uart1
  send_wait_time: 200ms

modbus_controller:
  - id: modbus_controller1
    modbus_id: modbus1
    ## the Modbus device addr
    address: 0x1
    setup_priority: -10

# ========================
#   modbus coil registers
# ========================

switch:
- platform: modbus_controller
  modbus_controller_id: modbus_controller1
  id: zone1_on_off
  name: "Zone 1 - On/Off"
  register_type: coil
  address: 0x0000
  bitmask: 1
  entity_category: config
  icon: "mdi:toggle-switch"

- platform: modbus_controller
  modbus_controller_id: modbus_controller1
  id: zone1_auto_swing
  name: "Zone 1 - Auto Swing"
  register_type: coil
  address: 0x0001
  bitmask: 1
  entity_category: config
  icon: "mdi:toggle-switch"

Any help here is greatly appreciated.