I have successfully installed modbus bridge, i have defined RX/TX pins and connected them to Ouman H23 RTU slave pins. With CAS modbus scanner i can connect to the esp, but im just receiving connection timeouts on every register. I have tried to reverse RX/TX pins, no change.
in esphome logs i see:
[17:59:08.144][W][modbus_bridge:886]: Modbus timeout: no response received (no first byte) client_id=1
any ideas ?
I also tried to configure it to homeassistant:
Ouman H23 modbus doc:
name_tr="Outdoor temp." pointtype="6" registertype="Holding" addressformat="S32" addressindex="201" categorytype="2" unit="°C" decimals="1" scaling="10" readacceslevel="5" writeacceslevel="1" min="-50" max="130" type="0" iotype="1" />
configuration.yaml:
- name: ouman
type: tcp
timeout: 5
host: !secret ouman_host
port: 502
sensors:
- name: "Ouman Ulkolämpötila"
unique_id: ouman_outdoor_temp_201
address: 200
input_type: holding
data_type: int32
scale: 0.1
precision: 1
unit_of_measurement: "°C"
scan_interval: 60
Esphome config:
esphome:
name: esphome-web-0cd233
friendly_name: Modbus bridge
min_version: 2025.9.0
name_add_mac_suffix: false
esp8266:
board: esp01_1m
external_components:
- source:
type: git
url: https://github.com/rosenrot00/esphome_modbus_bridge
components: [modbus_bridge]
uart:
id: uart_bus
tx_pin: GPIO01
rx_pin: GPIO03
baud_rate: 9600
stop_bits: 1
rx_buffer_size: 256 # minimum 256 recommended; increase for long RTU responses
# Modbus bridge configuration
modbus_bridge:
id: mb_bridge
uart_id: uart_bus
tcp_port: 502 # TCP port to listen on
tcp_poll_interval: 50 # ms between TCP polls
tcp_client_timeout: 60000 # ms of inactivity before client is disconnected
tcp_allowed_clients: 4 # number of simultaneous TCP clients (min 1)
rtu_response_timeout: 3000 # ms, internally clamped to >=10 ms
#flow_control_pin: GPIO18 # optional: RS-485 DE/RE pin
on_tcp_clients_changed:
then:
- lambda: |-
id(tcp_clients) = count;
- logger.log:
format: "TCP clients connected: %d"
args: ['count']
# Other available events (use similarly):
# on_rtu_send: # (function_code, address) – triggered for every RTU command sent
# on_rtu_receive: # (function_code, address) – triggered for every valid RTU response
# on_rtu_timeout: # (function_code, address) – triggered for RTU timeouts
# on_tcp_started: # () – triggered when TCP server successfully starts
# on_tcp_stopped: # () – triggered when TCP server stops or IP is lost
# Output and LED for visual feedback
output:
- platform: gpio
id: output_led_status
pin: GPIO2
light:
- platform: binary
id: led_status
name: "Status LED"
output: output_led_status
# Global variable to hold number of connected TCP clients
globals:
- id: tcp_clients
type: int
restore_value: no
initial_value: '0'
# Every 3 s: blink LED as many times as connected TCP clients (100 ms per blink)
interval:
- interval: 3s
then:
- if:
condition:
lambda: 'return id(tcp_clients) > 0;'
then:
- repeat:
count: !lambda 'return id(tcp_clients);'
then:
- light.turn_on: led_status
- delay: 100ms
- light.turn_off: led_status
- delay: 100ms # short pause between blinks
# Debug switch for enabling verbose Modbus logging
switch:
- platform: template
name: "Modbus Bridge Debug"
id: modbus_debug_switch
restore_mode: RESTORE_DEFAULT_OFF
turn_on_action:
- lambda: |-
id(mb_bridge).set_debug(true);
id(modbus_debug_switch).publish_state(true);
turn_off_action:
- lambda: |-
id(mb_bridge).set_debug(false);
id(modbus_debug_switch).publish_state(false);
# Enable logging
logger:
baud_rate: 0
# Enable Home Assistant API
api:
# Allow Over-The-Air updates
ota:
- platform: esphome
wifi:
ssid: !secret wifi_ssid
password: !secret wifi_password
