@dc42 Thank you sir! works perfectly!

I can display the Duet 3 6HC mcu and drivers temp with

M308 S10 Y"mcu-temp" A"6HC MCU"
M308 S11 Y"drivers" A"6HC Steppers"

But How do get the same info from expansion boards?

Cheers.

@phaedrux Thank you for your reply.
Yes indeed, this is just with the printer sitting idle.

I did switch back to 3.3 last night and I am happy to report that I don't see the issue this morning.
I will report back if I ever encounter it again, but it seems I have encountered a bug in 3.4 that is not present in 3.3.

Bed heater no longer working after some time.
This is the 3rd morning I see this happening and I'm not sure what's going on: Last night I printed a part untill 2am, and this morning, I go to heat my bed and nothing happens. No fault, no temp rise.

Diag info.

2/19/2021, 10:18:13 AM	M122
=== Diagnostics ===
RepRapFirmware for Duet 2 WiFi/Ethernet version 3.4.0beta7 (2021-12-16 12:22:11) running on Duet WiFi 1.02 or later + DueX5
Board ID: 08DJM-9178L-L4MSJ-6J1F8-3S86M-K82YN
Used output buffers: 3 of 24 (24 max)
=== RTOS ===
Static ram: 23804
Dynamic ram: 74372 of which 28 recycled
Never used RAM 10180, free system stack 110 words
Tasks: NETWORK(ready,13.8%,232) HEAT(notifyWait,0.1%,311) Move(notifyWait,0.0%,283) DUEX(notifyWait,0.0%,24) MAIN(running,86.1%,416) IDLE(ready,0.0%,30), total 100.0%
Owned mutexes: WiFi(NETWORK)
=== Platform ===
Last reset 09:08:43 ago, cause: software
Last software reset at 2021-12-19 01:09, reason: User, GCodes spinning, available RAM 10612, slot 1
Software reset code 0x0003 HFSR 0x00000000 CFSR 0x00000000 ICSR 0x0041f000 BFAR 0xe000ed38 SP 0x00000000 Task MAIN Freestk 0 n/a
Error status: 0x14
Step timer max interval 0
MCU temperature: min 40.6, current 40.8, max 41.4
Supply voltage: min 24.2, current 24.3, max 24.6, under voltage events: 0, over voltage events: 0, power good: yes
Heap OK, handles allocated/used 99/0, heap memory allocated/used/recyclable 2048/84/84, gc cycles 0
Events: 0 queued, 0 completed
Driver 0: pos 66000, standstill, SG min n/a
Driver 1: pos -66000, standstill, SG min n/a
Driver 2: pos 14042, standstill, SG min n/a
Driver 3: pos 0, standstill, SG min n/a
Driver 4: pos 0, standstill, SG min n/a
Driver 5: pos 0, standstill, SG min n/a
Driver 6: pos 0, standstill, SG min n/a
Driver 7: pos 0, standstill, SG min n/a
Driver 8: pos 0, standstill, SG min n/a
Driver 9: pos 0, standstill, SG min n/a
Driver 10: pos 0
Driver 11: pos 0
Date/time: 2021-12-19 10:18:11
Cache data hit count 4294967295
Slowest loop: 8.79ms; fastest: 0.18ms
I2C nak errors 0, send timeouts 0, receive timeouts 0, finishTimeouts 0, resets 0
=== Storage ===
Free file entries: 10
SD card 0 detected, interface speed: 20.0MBytes/sec
SD card longest read time 1.4ms, write time 0.0ms, max retries 0
=== Move ===
DMs created 83, segments created 35, maxWait 0ms, bed compensation in use: none, comp offset 0.000
=== MainDDARing ===
Scheduled moves 2900, completed 2900, hiccups 0, stepErrors 0, LaErrors 0, Underruns [0, 0, 0], CDDA state -1
=== AuxDDARing ===
Scheduled moves 0, completed 0, hiccups 0, stepErrors 0, LaErrors 0, Underruns [0, 0, 0], CDDA state -1
=== Heat ===
Bed heaters 0 -1 -1 -1, chamber heaters -1 -1 -1 -1, ordering errs 0
Heater 0 is on, I-accum = nan
Heater 1 is on, I-accum = 0.3
=== GCodes ===
Segments left: 0
Movement lock held by null
HTTP is idle in state(s) 0
Telnet is idle in state(s) 0
File is idle in state(s) 0
USB is idle in state(s) 0
Aux is idle in state(s) 0
Trigger is idle in state(s) 0
Queue is idle in state(s) 0
LCD is idle in state(s) 0
Daemon is idle in state(s) 0
Autopause is idle in state(s) 0
Code queue is empty
=== DueX ===
Read count 0, 0.00 reads/min
=== Network ===
Slowest loop: 199.78ms; fastest: 0.09ms
Responder states: HTTP(0) HTTP(0) HTTP(0) HTTP(0) FTP(0) Telnet(0), 0 sessions
HTTP sessions: 2 of 8
- WiFi -
Network state is active
WiFi module is connected to access point 
Failed messages: pending 0, notready 0, noresp 2
WiFi firmware version 1.23
WiFi MAC address 84:f3:eb:ea:60:32
WiFi Vcc 3.35, reset reason Power up
WiFi flash size 4194304, free heap 22792
WiFi IP address 192.168.3.109
WiFi signal strength -59dBm, mode none, reconnections 0, sleep mode modem
Clock register ffffffff
Socket states: 0 0 0 0 0 0 0 0

If I power off and on again, it works normally again.

FYI I just upgraded from v2 to latest beta a few days ago, without touching any wiring. This printer had been running stable for the past 2 years before this, so I don't think it's a wiring issue.

What has changed in the bed heating config compared to v2 is the the Q10 parameter:
M950 H0 Q10 C"bedheat" T0, which is recommended for SSR. After a pid tuning, my heat bed heats quite differently than before (in multiple pulses every second, vs in long 3-4 second pulses before).

Anyways, it seems that after a few hours of sitting idle it doesn't respond to commands anymore, and I don't get any faults either.

Let me know what you think!