MBUS input failing

Emoncms
1

I’ve been getting increasingly frequent MBUS failures (8, 13, 17, 22, 22, 27, 29th March). They are resolved by rebooting the Pi.

The last entries in emonhub.log before the failure were
2026-03-29 00:16:50,748 DEBUG    MQTT       Publishing: emon/heatpump/heatmeter_ManSpec 25156
2026-03-29 00:16:50,749 DEBUG    MQTT       Publishing: emon/heatpump/heatmeter_heat_calc 7714.757777777776
2026-03-29 00:16:50,849 DEBUG    DS18B20    28-0822548fb0f9: 28-0822548fb0f9 10.062
2026-03-29 00:16:51,649 DEBUG    DS18B20    28-0922545e4ea8: 28-0922545e4ea8 42.187
2026-03-29 00:16:52,513 DEBUG    DS18B20    28-092254988d29: 28-092254988d29 41.5
2026-03-29 00:16:52,514 DEBUG    DS18B20    420 NEW FRAME :
2026-03-29 00:16:52,514 DEBUG    DS18B20    420 Timestamp : 1774743410.040637
2026-03-29 00:16:52,515 DEBUG    DS18B20    420 From Node : sensors
2026-03-29 00:16:52,515 DEBUG    DS18B20    420    Values : [10.062, 42.187, 41.5]
2026-03-29 00:16:52,515 DEBUG    DS18B20    420 Sent to channel(start)’ : ToEmonCMS
2026-03-29 00:16:52,516 DEBUG    DS18B20    420 Sent to channel(end)’ : ToEmonCMS
2026-03-29 00:16:52,557 DEBUG    MQTT       Publishing: emon/sensors/28-0822548fb0f9 10.062
2026-03-29 00:16:52,558 DEBUG    MQTT       Publishing: emon/sensors/28-0922545e4ea8 42.187
2026-03-29 00:16:52,559 DEBUG    MQTT       Publishing: emon/sensors/28-092254988d29 41.5
2026-03-29 00:16:55,555 DEBUG    EmonPi2    423 NEW FRAME : MSG:54721,Vrms:240.00,P1:3,P2:2,P3:2,P4:2,P5:2,P6:65,E1:371774,E2:29226,E3:28576,E4:27385,E5:18590,E6:53028,pulse:1713061,analog:231
2026-03-29 00:16:55,556 DEBUG    EmonPi2    423 Timestamp : 1774743415.555125
2026-03-29 00:16:55,556 DEBUG    EmonPi2    423 From Node : EmonPi2
2026-03-29 00:16:55,556 DEBUG    EmonPi2    423    Values : [54721, 240, 3, 2, 2, 2, 2, 65, 371774, 29226, 28576, 27385, 18590, 53028, 1713061, 231, 0, 0.0]
2026-03-29 00:16:55,557 DEBUG    EmonPi2    423 Sent to channel(start)’ : ToEmonCMS
2026-03-29 00:16:55,557 DEBUG    EmonPi2    423 Sent to channel(end)’ : ToEmonCMS
2026-03-29 00:16:55,766 DEBUG    MQTT       Publishing: emon/EmonPi2/MSG 54721
2026-03-29 00:16:55,767 DEBUG    MQTT       Publishing: emon/EmonPi2/Vrms 240
2026-03-29 00:16:55,768 DEBUG    MQTT       Publishing: emon/EmonPi2/P1 3
2026-03-29 00:16:55,769 DEBUG    MQTT       Publishing: emon/EmonPi2/P2 2
2026-03-29 00:16:55,769 DEBUG    MQTT       Publishing: emon/EmonPi2/P3 2
2026-03-29 00:16:55,770 DEBUG    MQTT       Publishing: emon/EmonPi2/P4 2
2026-03-29 00:16:55,771 DEBUG    MQTT       Publishing: emon/EmonPi2/P5 2
2026-03-29 00:16:55,771 DEBUG    MQTT       Publishing: emon/EmonPi2/P6 65
2026-03-29 00:16:55,772 DEBUG    MQTT       Publishing: emon/EmonPi2/E1 371774
2026-03-29 00:16:55,772 DEBUG    MQTT       Publishing: emon/EmonPi2/E2 29226
2026-03-29 00:16:55,773 DEBUG    MQTT       Publishing: emon/EmonPi2/E3 28576
2026-03-29 00:16:55,774 DEBUG    MQTT       Publishing: emon/EmonPi2/E4 27385
2026-03-29 00:16:55,775 DEBUG    MQTT       Publishing: emon/EmonPi2/E5 18590
2026-03-29 00:16:55,775 DEBUG    MQTT       Publishing: emon/EmonPi2/E6 53028
2026-03-29 00:16:55,776 DEBUG    MQTT       Publishing: emon/EmonPi2/pulse 1713061
2026-03-29 00:16:55,776 DEBUG    MQTT       Publishing: emon/EmonPi2/analog 231
2026-03-29 00:16:55,777 DEBUG    MQTT       Publishing: emon/EmonPi2/missed 0
2026-03-29 00:16:55,778 DEBUG    MQTT       Publishing: emon/EmonPi2/missedprc 0.0
2026-03-29 00:17:00,446 DEBUG    SDM120     [3241.8, 11148.315]
2026-03-29 00:17:00,447 DEBUG    SDM120     426 NEW FRAME :
2026-03-29 00:17:00,447 DEBUG    SDM120     426 Timestamp : 1774743420.078422
2026-03-29 00:17:00,448 DEBUG    SDM120     426 From Node : heatpump
2026-03-29 00:17:00,448 DEBUG    SDM120     426    Values : [3241.8, 11148.315]
2026-03-29 00:17:00,449 DEBUG    SDM120     426 Sent to channel(start)’ : ToEmonCMS
2026-03-29 00:17:00,449 DEBUG    SDM120     426 Sent to channel(end)’ : ToEmonCMS
2026-03-29 00:17:00,591 DEBUG    MQTT       Publishing: emon/heatpump/electric_Power 3241.8
2026-03-29 00:17:00,592 DEBUG    MQTT       Publishing: emon/heatpump/electric_Energy 11148.315
2026-03-29 00:17:00,619 DEBUG    MBUS       Invalid MBUS data received 105 bytes 609.0 ms, count: 102
2026-03-29 00:17:00,621 DEBUG    MBUS       Decoded MBUS data: {“DateTime”: [861733394, “”], “DateTime_error”: [16842752, “”], “Record_error”: [0, “”], “Ontime”: [46453051, “s”], “OperatingTime”: [46446069, “s”], “Energy”: [38310, “kWh”], “Cooling”: [1240, “kWh”], “Volume”: [9057.861, “m3”], “Power”: [7618, “W”], “FlowRate”: [1.202, “m3/h”], “FlowT”: [50.42, “C”], “ReturnT”: [44.9, “C”], “DeltaT”: [5.5200000000000005, “C”], “FabNo”: [4030914, “”], “ManSpec”: [15102, “”], “heat_calc”: [7648.726666666672, “W”]}
2026-03-29 00:17:00,621 DEBUG    MBUS       424 NEW FRAME :
2026-03-29 00:17:00,622 DEBUG    MBUS       424 Timestamp : 1774743420.010596
2026-03-29 00:17:00,622 DEBUG    MBUS       424 From Node : heatpump
2026-03-29 00:17:00,622 DEBUG    MBUS       424    Values : [861733394, 16842752, 0, 46453051, 46446069, 38310, 1240, 9057.861, 7618, 1.202, 50.42, 44.9, 5.5200000000000005, 4030914, 15102, 7648.726666666672]
2026-03-29 00:17:00,623 DEBUG    MBUS       424 Sent to channel(start)’ : ToEmonCMS
2026-03-29 00:17:00,623 DEBUG    MBUS       424 Sent to channel(end)’ : ToEmonCMS
2026-03-29 00:17:00,794 DEBUG    MQTT       Publishing: emon/heatpump/heatmeter_DateTime 861733394
2026-03-29 00:17:00,795 DEBUG    MQTT       Publishing: emon/heatpump/heatmeter_DateTime_error 16842752
2026-03-29 00:17:00,796 DEBUG    MQTT       Publishing: emon/heatpump/heatmeter_Record_error 0
2026-03-29 00:17:00,797 DEBUG    MQTT       Publishing: emon/heatpump/heatmeter_Ontime 46453051
2026-03-29 00:17:00,797 DEBUG    MQTT       Publishing: emon/heatpump/heatmeter_OperatingTime 46446069
2026-03-29 00:17:00,798 DEBUG    MQTT       Publishing: emon/heatpump/heatmeter_Energy 38310
2026-03-29 00:17:00,799 DEBUG    MQTT       Publishing: emon/heatpump/heatmeter_Cooling 1240
2026-03-29 00:17:00,799 DEBUG    MQTT       Publishing: emon/heatpump/heatmeter_Volume 9057.861
2026-03-29 00:17:00,800 DEBUG    MQTT       Publishing: emon/heatpump/heatmeter_Power 7618
2026-03-29 00:17:00,800 DEBUG    MQTT       Publishing: emon/heatpump/heatmeter_FlowRate 1.202
2026-03-29 00:17:00,801 DEBUG    MQTT       Publishing: emon/heatpump/heatmeter_FlowT 50.42
2026-03-29 00:17:00,802 DEBUG    MQTT       Publishing: emon/heatpump/heatmeter_ReturnT 44.9
2026-03-29 00:17:00,802 DEBUG    MQTT       Publishing: emon/heatpump/heatmeter_DeltaT 5.5200000000000005
2026-03-29 00:17:00,803 DEBUG    MQTT       Publishing: emon/heatpump/heatmeter_FabNo 4030914
2026-03-29 00:17:00,804 DEBUG    MQTT       Publishing: emon/heatpump/heatmeter_ManSpec 15102
2026-03-29 00:17:00,804 DEBUG    MQTT       Publishing: emon/heatpump/heatmeter_heat_calc 7648.726666666672
2026-03-29 00:17:00,833 DEBUG    DS18B20    28-0822548fb0f9: 28-0822548fb0f9 10.062

Although the log stopped at 00:17:00,833 the heat output and flow and return temperatures continue in the app until 00:32 at which point they disappear until I rebooted the Pi

The next rotated log started at 02:00:03 with the following MBUS entries


2026-03-29 02:00:10,048 ERROR    MBUS       Could not find MBUS device
2026-03-29 02:00:10,048 ERROR    MBUS       Could not write to MBUS serial port
2026-03-29 02:00:10,048 ERROR    MBUS       read_data_frame could not read from serial port
2026-03-29 02:00:10,048 DEBUG    MBUS       Invalid MBUS data received 0 bytes 0.1 ms, count: 1
2026-03-29 02:00:10,249 ERROR    MBUS       Could not write to MBUS serial port
2026-03-29 02:00:10,249 ERROR    MBUS       read_data_frame could not read from serial port
2026-03-29 02:00:10,249 DEBUG    MBUS       Invalid MBUS data received 0 bytes 0.1 ms, count: 2
2026-03-29 02:00:10,449 DEBUG    MBUS       Decoded MBUS data: None

Any thoughts as to what might be causing this? I do get power cuts occasionally - could my SD card be corrupted?

2

Have you checked the space on the SD Card?

3

Yes thanks - have run df - no partitions anywhere near full

1 Like
4

It could be the USB MBUS device that is failing. If there are no other symptoms, I’d be surprised if it is the SD Card. How old is the system/Card?

Is it an emonHP? If so contact the shop.

5

The system and card are 16 months old. Rebooting brings MBUS data back although as I understand it, rebooting doesn’t remove 5V from USB ports.

It is an emonHP so I’ll contact the shop although first I’ll wait for the next failure and run journalctl before rebooting and observe the MBUS LED when I do reboot.

Thanks for the advice

6

No a reboot does not power down. If you can access it, I’d suggest a powerdown, remove power and then re power might help, but the MBUS should be more reliable than that (and usually is).

7

Hi Nick,

Sorry to hear you’re having issues. I’ve had a look at your data and I can see the MBUS outage always seems to coincide with DHW cycle. I think the issue might be interference from the diverter valve. Can you try and make sure the MBUS cable is routed away from 240V cables? Especially the diverter valve cable, which will be subject to back EMF.