ESP32-C6-WROOM-1 Development board up and running

[AndriesMuylaert]

Hi there,

I have my ESP32-C6-WROOM-1 Development board up-and-running on my Daikin Altherma EHBH16C9W.
See: https://github.com/AndriesMuylaert/esphome-altherma/blob/main/esphome-altherma-esp32-c6.yaml
Other changes are well described in the commits.

Main advantage of this board:
Includes 1 5 amps relais that can be used to power the contactor to heat the water in the water tank (or any other purpose).
Includes also some internal sensors (internal temp, uptime, wifi signal strength, on-board boot button).

Everything seems to work fine but I receive sometimes timeouts in the logs.
See example log:
[22:49:34.924][D][sensor:124]: 'Internal Temperature' >> 25.0 °C
[22:49:36.903][D][altherma_hub:050]: Update start
[22:49:36.907][D][altherma_hub:056]: Register 0x20
[22:49:36.937][E][altherma_hub:124]: CRC Invalid: 0x00 (expected 0x7f)
[22:49:36.938][D][altherma_hub:056]: Register 0x21
[22:49:36.938][E][altherma_hub:124]: CRC Invalid: 0x00 (expected 0xb4)
[22:49:36.941][D][altherma_hub:056]: Register 0x30
[22:49:37.056][E][altherma_hub:116]: Timeout waiting for response for register 0x30
[22:49:37.061][D][altherma_hub:056]: Register 0x60
[22:49:37.079][D][altherma_hub:134]: Query register 0x60 OK CRC: 0x65 Length: 0x13 Time: 31 ms
[22:49:37.082][D][sensor:124]: 'DHW setpoint' >> 52.0 °C
[22:49:37.082][D][sensor:124]: 'LW setpoint (main)' >> 33.5 °C
[22:49:37.082][D][text_sensor:120]: 'I⁄U operation mode' >> 'Heating'
[22:49:37.082][D][text_sensor:120]: 'Error Code' >> ' 0'
[22:49:37.088][D][text_sensor:120]: 'Error detailed code' >> '0'
[22:49:37.088][D][text_sensor:120]: 'Error type' >> 'Normal'
[22:49:37.088][D][altherma_hub:056]: Register 0x61
[22:49:37.190][E][altherma_hub:116]: Timeout waiting for response for register 0x61
[22:49:37.205][D][altherma_hub:056]: Register 0x62
[22:49:37.226][D][altherma_hub:134]: Query register 0x62 OK CRC: 0xbe Length: 0x10 Time: 38 ms
[22:49:37.236][D][sensor:124]: 'Flow sensor (l⁄min)' >> 32.8 l/min
[22:49:37.236][D][sensor:124]: 'Water pressure (bar)' >> 0.0 bar
[22:49:37.247][D][sensor:124]: 'Water pump signal (0:max-100:stop)' >> 30
[22:49:37.247][D][altherma_hub:056]: Register 0x10
[22:49:37.335][E][altherma_hub:116]: Timeout waiting for response for register 0x10
[22:49:37.335][D][altherma_hub:072]: Update end
[22:49:38.457][D][sensor:124]: 'Uptime' >> 1504 s
[22:49:39.393][D][sensor:124]: 'WiFi Signal Strength' >> -60 dBm
[22:50:06.908][D][altherma_hub:050]: Update start
[22:50:06.909][D][altherma_hub:056]: Register 0x20
[22:50:06.963][E][altherma_hub:124]: CRC Invalid: 0x00 (expected 0x32)
[22:50:06.966][D][altherma_hub:056]: Register 0x21
[22:50:07.053][E][altherma_hub:116]: Timeout waiting for response for register 0x21
[22:50:07.054][D][altherma_hub:056]: Register 0x30
[22:50:07.081][D][altherma_hub:134]: Query register 0x30 OK CRC: 0x05 Length: 0x0d Time: 25 ms
[22:50:07.084][D][sensor:124]: 'INV frequency (rps)' >> 54 rps
[22:50:07.088][D][sensor:124]: 'Fan 1 (10 rpm)' >> 540 rpm
[22:50:07.088][D][sensor:124]: 'Fan 2 (step)' >> 8 rpm
[22:50:07.094][D][altherma_hub:056]: Register 0x60
[22:50:07.131][D][altherma_hub:134]: Query register 0x60 OK CRC: 0x65 Length: 0x13 Time: 35 ms
[22:50:07.131][D][sensor:124]: 'DHW setpoint' >> 52.0 °C
[22:50:07.131][D][sensor:124]: 'LW setpoint (main)' >> 33.5 °C
[22:50:07.134][D][text_sensor:120]: 'I⁄U operation mode' >> 'Heating'
[22:50:07.134][D][text_sensor:120]: 'Error Code' >> ' 0'
[22:50:07.135][D][text_sensor:120]: 'Error detailed code' >> '0'
[22:50:07.135][D][text_sensor:120]: 'Error type' >> 'Normal'
[22:50:07.155][D][altherma_hub:056]: Register 0x61
[22:50:07.259][E][altherma_hub:116]: Timeout waiting for response for register 0x61
[22:50:07.259][D][altherma_hub:056]: Register 0x62
[22:50:07.269][D][altherma_hub:134]: Query register 0x62 OK CRC: 0xc2 Length: 0x10 Time: 29 ms
[22:50:07.278][D][sensor:124]: 'Flow sensor (l⁄min)' >> 32.4 l/min
[22:50:07.278][D][sensor:124]: 'Water pressure (bar)' >> 0.0 bar
[22:50:07.278][D][sensor:124]: 'Water pump signal (0:max-100:stop)' >> 30
[22:50:07.278][D][altherma_hub:056]: Register 0x10
[22:50:07.372][E][altherma_hub:116]: Timeout waiting for response for register 0x10
[22:50:07.429][D][altherma_hub:072]: Update end

You can include this YAML in your branch.

Best regards

[jjohnsen]

Hi,

Thanks for sharing your setup and configuration!

Regarding the timeouts, do you have an idea how frequently they occur?

Perhaps you could try increasing the timeout value (currently 100 ms) in altherma_hub.cpp ?

[jjohnsen]

@AndriesMuylaert 've published a new release that improves the internal handling of the component, especially around UART communication. It should reduce the risk of timeouts.
Could you give it a try and see if it resolves the issues you're seeing in the logs?

[AndriesMuylaert]

@jjohnsen ,
I have tried the latest Release but receive error while compiling. Could also be related to the update from ESPHome 2026.4.0 because I have the same issue with the previous build.

INFO ESPHome 2026.4.0
INFO Reading configuration /config/esphome/esphome-web-128b58.yaml...
INFO Generating C++ source...
INFO Setting CONFIG_LWIP_MAX_SOCKETS to 12 (TCP=6 [api=3, captive_portal=3], UDP=3 [captive_portal=1, mdns=2], TCP_LISTEN=3 [api=1, ota=1, web_server_base=1])
INFO Compiling app... Build path: /data/build/esphome-web-128b58
Processing esphome-web-128b58 (board: esp32-c6-devkitm-1; framework: espidf; platform: https://github.com/pioarduino/platform-espressif32/releases/download/55.03.38-1/platform-espressif32.zip)

HARDWARE: ESP32C6 160MHz, 320KB RAM, 4MB Flash

• contrib-piohome @ 3.4.4
• framework-espidf @ 3.50504.0 (5.5.4)
• tool-cmake @ 4.0.3
• tool-esp-rom-elfs @ 2024.10.11
• tool-esptoolpy @ 5.2.0
• tool-ninja @ 1.13.1
• tool-riscv32-esp-elf-gdb @ 16.3.0+20250913
• tool-scons @ 4.40801.0 (4.8.1)
• toolchain-riscv32-esp @ 14.2.0+20260121
  Using Python 3.12.10 environment at: /root/.platformio/penv/.espidf-5.5.4
  Reading CMake configuration...
  Generating assembly for certificate bundle...
  Dependency Graph
  |-- noise-c @ 0.1.11
  Compiling .pioenvs/esphome-web-128b58/src/esphome/components/altherma_hub/altherma_hub.cpp.o
  Compiling .pioenvs/esphome-web-128b58/src/esphome/components/api/api_buffer.cpp.o
  In file included from src/esphome/components/altherma_hub/altherma_hub.cpp:3:
  src/esphome/components/altherma_hub/mock_uart.h:25:28: error: 'FlushResult' in namespace 'esphome::uart' does not name a type; did you mean 'UARTFlushResult'?
  25 | esphome::uart::FlushResult flush() override {
  | ^~~~~~~~~~~
  | UARTFlushResult
  *** [.pioenvs/esphome-web-128b58/src/esphome/components/altherma_hub/altherma_hub.cpp.o] Error 1
  ========================= [FAILED] Took 132.35 seconds =========================

[AndriesMuylaert]

In ESPHome 2026.4.0, the FlushResult enum was renamed to UARTFlushResult and all enum values got a UART_FLUSH_RESULT_ prefix — a breaking change introduced to avoid macro collisions with the Realtek RTL SDK's #define SUCCESS 0. Esphome
So UARTFlushResult::SUCCESS → UARTFlushResult::UART_FLUSH_RESULT_SUCCESS.

[jjohnsen]

@AndriesMuylaert, yes I'm aware of the change in 2026.4.0 (#17), , but I’ve held off on adding it until 2026.4.0 is released as stable.
Could you try compiling with the previous version of ESPHome 2026.3.3?

[AndriesMuylaert]

Hello @jjohnsen,

Here is an update on my configuration:

• I have rebased to your new release.
• I have switched successfully to Seedstudio XIAO ESP32-C6 XIAO YAML and ESPHome 2026.4.0
• Timeouts seems to be disappeared, all seems to be working fine.
• I noticed recently that some sensors always have '0' as a value (or not provided):
  INV frequency (rps), INV Primary current (A), INV Secondary current (A) and some more...
  What is a good starting point to solve this? Is there any documentation available ?
  I guess I need a different config file for my mainboard 2P300920-3

For info:
[10:27:45.824][C][mdns:194]: Hostname: esphome-web-***
[10:27:47.534][S][sensor]: 'WiFi Signal Strength' >> -90 dBm
[10:27:47.772][S][sensor]: 'Internal Temperature' >> 33.2 °C
[10:27:49.177][S][sensor]: 'Uptime' >> 69004 s
[10:27:51.318][D][altherma_hub:059]: Update start
[10:27:51.354][D][altherma_hub:219]: Query register 0x20 OK CRC: 0x54 Length: 0x13 Time: 34 ms
[10:27:51.386][D][altherma_hub:219]: Query register 0x21 OK CRC: 0x95 Length: 0x09 Time: 22 ms
[10:27:51.421][D][altherma_hub:219]: Query register 0x30 OK CRC: 0x02 Length: 0x0d Time: 25 ms
[10:27:51.455][S][sensor]: 'Outdoor air temp. (R1T)' >> 11.7 °C
[10:27:51.455][S][sensor]: 'Discharge pipe temp.' >> 14.7 °C
[10:27:51.455][S][sensor]: 'Heat exchanger mid-temp.' >> 12.5 °C
[10:27:51.455][S][sensor]: 'Heat sink temp.' >> 16.8 °C
[10:27:51.455][S][sensor]: 'INV primary current (A)' >> 0.0 A
[10:27:51.455][S][sensor]: 'INV secondary current (A)' >> 0.0 A
[10:27:51.455][S][sensor]: 'Voltage (N-phase) (V)' >> 0 V
[10:27:51.455][S][sensor]: 'INV frequency (rps)' >> 0 rps
[10:27:51.456][S][sensor]: 'Fan 1 (10 rpm)' >> 0 rpm
[10:27:51.456][S][sensor]: 'Fan 2 (step)' >> 0 rpm
[10:27:51.466][D][altherma_hub:219]: Query register 0x60 OK CRC: 0x70 Length: 0x13 Time: 32 ms
[10:27:51.506][D][altherma_hub:219]: Query register 0x61 OK CRC: 0xad Length: 0x12 Time: 33 ms
[10:27:51.573][D][altherma_hub:219]: Query register 0x62 OK CRC: 0xcd Length: 0x10 Time: 33 ms
[10:27:51.577][S][sensor]: 'DHW setpoint' >> 52.0 °C
[10:27:51.578][S][sensor]: 'LW setpoint (main)' >> 35.0 °C
[10:27:51.578][S][text_sensor]: 'I⁄U operation mode' >> 'DHW'
[10:27:51.578][S][text_sensor]: 'Error Code' >> ' 0'
[10:27:51.578][S][text_sensor]: 'Error detailed code' >> '0'
[10:27:51.578][S][text_sensor]: 'Error type' >> 'Normal'
[10:27:51.578][S][sensor]: 'Leaving water temp. before BUH (R1T)' >> 23.2 °C
[10:27:51.578][S][sensor]: 'Leaving water temp. after BUH (R2T)' >> 21.7 °C
[10:27:51.578][S][sensor]: 'Refrig. Temp. liquid side (R3T)' >> 22.1 °C
[10:27:51.578][S][sensor]: 'Inlet water temp. (R4T)' >> 22.5 °C
[10:27:51.578][S][sensor]: 'DHW tank temp. (R5T)' >> 44.8 °C
[10:27:51.578][S][sensor]: 'Indoor ambient temp. (R1T)' >> 22.3 °C
[10:27:51.578][S][sensor]: 'Flow sensor (l⁄min)' >> -0.6 l⁄min
[10:27:51.579][S][sensor]: 'Water pressure (bar)' >> 0.0 bar
[10:27:51.579][S][sensor]: 'Water pump signal (0:max-100:stop)' >> 100
[10:27:51.600][D][altherma_hub:219]: Query register 0x10 OK CRC: 0x33 Length: 0x12 Time: 32 ms
[10:27:51.611][D][altherma_hub:230]: Update end (276 ms)

Thank you for your great work !

[jjohnsen]

Great to see the timeouts are gone!

It’s a bit unusual that you’re missing inverter values, and also that leaving water temperature is lower than inlet water temperature.
Is this consistent, or could it be that the inverter was off when the log was taken?

[AndriesMuylaert]

Update:
It was rather hot last days and heat pump was not working.
I do receive values for INV frequency (rps), INV Primary current (A), INV Secondary current (A),
the only ones still missing are 'Voltage (N-phase) (V)' and 'Water pressure (bar)'.

For info:
[16:07:21.552][D][altherma_hub:059]: Update start
[16:07:21.589][D][altherma_hub:219]: Query register 0x20 OK CRC: 0x8c Length: 0x13 Time: 35 ms
[16:07:21.629][D][altherma_hub:219]: Query register 0x21 OK CRC: 0x2e Length: 0x09 Time: 25 ms
[16:07:21.664][D][altherma_hub:219]: Query register 0x30 OK CRC: 0x8c Length: 0x0d Time: 26 ms
[16:07:21.704][S][sensor]: 'Outdoor air temp. (R1T)' >> 12.2 °C
[16:07:21.704][S][sensor]: 'Discharge pipe temp.' >> 69.9 °C
[16:07:21.705][S][sensor]: 'Heat exchanger mid-temp.' >> 10.1 °C
[16:07:21.705][S][sensor]: 'Heat sink temp.' >> 36.6 °C
[16:07:21.705][S][sensor]: 'INV primary current (A)' >> 2.6 A
[16:07:21.705][S][sensor]: 'INV secondary current (A)' >> 7.7 A
[16:07:21.705][S][sensor]: 'Voltage (N-phase) (V)' >> 0 V
[16:07:21.705][S][sensor]: 'INV frequency (rps)' >> 24 rps
[16:07:21.705][S][sensor]: 'Fan 1 (10 rpm)' >> 240 rpm
[16:07:21.705][S][sensor]: 'Fan 2 (step)' >> 8 rpm
[16:07:21.709][D][altherma_hub:219]: Query register 0x60 OK CRC: 0xe6 Length: 0x13 Time: 33 ms
[16:07:21.750][D][altherma_hub:219]: Query register 0x61 OK CRC: 0xfa Length: 0x12 Time: 33 ms
[16:07:21.797][D][altherma_hub:219]: Query register 0x62 OK CRC: 0x13 Length: 0x10 Time: 33 ms
[16:07:21.823][S][sensor]: 'DHW setpoint' >> 52.0 °C
[16:07:21.824][S][sensor]: 'LW setpoint (main)' >> 35.0 °C
[16:07:21.824][S][text_sensor]: 'I⁄U operation mode' >> 'DHW'
[16:07:21.824][S][text_sensor]: 'Error Code' >> ' 0'
[16:07:21.824][S][text_sensor]: 'Error detailed code' >> '0'
[16:07:21.824][S][text_sensor]: 'Error type' >> 'Normal'
[16:07:21.824][S][sensor]: 'Leaving water temp. before BUH (R1T)' >> 49.0 °C
[16:07:21.824][S][sensor]: 'Leaving water temp. after BUH (R2T)' >> 48.9 °C
[16:07:21.824][S][sensor]: 'Refrig. Temp. liquid side (R3T)' >> 46.2 °C
[16:07:21.824][S][sensor]: 'Inlet water temp. (R4T)' >> 45.9 °C
[16:07:21.824][S][sensor]: 'DHW tank temp. (R5T)' >> 38.1 °C
[16:07:21.824][S][sensor]: 'Indoor ambient temp. (R1T)' >> 22.8 °C
[16:07:21.825][S][sensor]: 'Flow sensor (l⁄min)' >> 27.4 l⁄min
[16:07:21.825][S][sensor]: 'Water pressure (bar)' >> 0.0 bar
[16:07:21.825][S][sensor]: 'Water pump signal (0:max-100:stop)' >> 4
[16:07:21.839][D][altherma_hub:219]: Query register 0x10 OK CRC: 0x7e Length: 0x12 Time: 33 ms
[16:07:21.844][D][altherma_hub:230]: Update end (286 ms)

[jjohnsen]

Ok, good. What model is your indoor and outdoor model? Do you have water pressure on the units display? It might use a different register for the missing values.