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Troubleshooting

You find here problems and solutions collected by users. I spend some time to write this documentation. Please take your time to read it before you open a new issue.

If you can't find the solution for your problem here and not in the existing Issues you can open a new issue. But please consider the following topics:

  • You should have a basic understanding how to use an ESP8266. That includes the usage of an IDE for programming, compile, flash, OTA and log output via the serial terminal.
  • You should have a basic understanding of the MQTT protocol and how to setup a MQTT broker

There are great descriptions in the WWW related to the topics above. Please use your preferred search engine.

If you open a new issue, please consider the following topics:

  • Use a use a meaningful title, so that the next user with a similar problem can recognize it
  • Which program version do you use?
  • Add the exact name of your AC indoor unit, e.g. SRK 35 ZS-S
  • MHI-AC-Ctrl outputs some basic status information via the serial terminal. Please use it for your first analysis and upload it together with a new Issue. Check this section

Recording a basic log file

You can use e.g. the Arduino IDE to record the serial output. Apply a baud rate of 115000 Baud and switch on the time stamp. In order not to overload the Issue, the log should not be copied directly into the Issue, but copied to a text file and attached to the Issue.

Recording a detailed log of the SPI waveforms

This is done via the SPI-logger. You can use e.g. the Arduino IDE to record the serial output. Apply a baud rate of 115000 Baud and switch off the time stamp. In order not to overload the Issue, the log should not be copied directly into the Issue, but copied to a text file and attached to the Issue.

Known limitations

MHI-AC-Ctrl doesn't support all functions of the infrared remote control. This is because some functions are not reflected by the SPI payload (or I'm not aware of the according SPI codes):

  • Vanes up/down is supported, but with the limitation that if the last command was issued by the IR RC, then the vanes up/down status is not visible in MHI-AC-Ctrl
  • ECO, Silent and Night set back mode

This should be considered especially when you use the IR RC in parallel to MHI-AC-Ctrl.

🔥 ESP8266 crashes periodically

For a periodic crash there are different causes possible:

🔥 Pins not properly connected

During boot the frequency of the SPI pins are checked. This is very helpful to identify SPI signal connection problems. Following values are expected:

  • SCK frequency > 3000 Hz
  • MOSI frequency < SCK frequency (usually ~ 500 Hz)
  • MISO frequency ~ 0 Hz (usually 0Hz)

If you see other values, please re-check

  • the connection between the MHI-AC-Ctrl board and your AC
  • that there is no short between the three signals

If MISO frequency>10Hz the program will stop and reboot. This prevents damage of your board or AC because there was a signal detected on the MISO pin which should be an output during normal operation.

Typical faults seen in the past:

  • SCK frequency = 0Hz => SCK pin not connected
  • SCK frequency < MOSI frequency => SCK and MOSI pins swapped
  • MISO frequency = SCK frequency => MISO and SCK pins shorted

For reference: With a multimeter I measure for SCK and MOSI approx. 4.7V on the HV pins of the level shifter (and X1) and approx. 3V on the LV pins of the level shifter (and D5/D7)

🔥 You use PubSubClient v2.8.0

There was a bug introduced in PubSubClient version 2.8.0, please use v2.7.0.

🔥 MQTT connects / disconnects periodically

The HOSTNAME specified in support.h is used as WiFi hostname, MQTT hostname and OTA hostname. In case that you use more than one MHI-AC-Ctrl, e.g. in a multi-split configuration, you have to use unique HOSTNAME to every PCB.

🔥 AC switches power off sometimes

When there is for >=120 seconds no valid MISO frame, the AC goes into an error state (MQTT topic Errorcode=1) and the AC switches off. You can leave the error state by sending a command via IR-RC or by sending a command via SPI. To switch on the AC again via SPI you have to send the Power On command. I assume this is some kind of safety function. This happens when there is >=120 seconds no WiFi or MQTT connection, because the SW loop related to SPI is not served.

🔥 Receiving the AC status works, but can't change values

Different root causes are possible:

🔥 MISO pin not connected to AC

Please check this section

🔥 Wrong MQTT set path used

The MQTT path for receiving the status is different from the MQTT path for setting values. Re-check that you use the set-path described in SW-Configuration.md. Please pay attention to the case sensitivity.

🔥 Last Vanes up/down status not visible in MHI-AC-Ctrl

That is no bug, but a restriction because the SPI unfortunately doesn't provide the Vanes status when the IR remote control was used for the last command.

🔥 Log shows errors, but it works nevertheless

With some ACs the SPI connection is fragile because of a different timing. E.g.

mhi_ac_ctrl_core.loop error: -4

Possible error codes:

err_msg_invalid_signature = -1
err_msg_invalid_checksum = -2
err_msg_timeout_SCK_low = -3
err_msg_timeout_SCK_high = -4

However, this does not appear to be critical and is usually not noticed by the user.

🔥 Room temperature is toggling

This effect occurs with some AC models. The cause is unclear.

🔥 Can't see the device in in Arduino IDE 'tools -> port' for OTA

I believe this is a general OTA problem, not related to MHI-AC-Ctrl. I made good experience using espota.py instead of the Arduino IDE for OTA.