Lost communication with mcu upon Bed Heating

General Discussion
1

Hello, I have an SKR 2 and a raspberry pi 4 running klipper. My problem is that whenever I’m trying to heat the bed by setting any temperature, I get an error “lost communication with mcu”.

When I remove the bed thermistor from the SKR 2 board and add an external thermistor to the same pin on SKR 2, the bed starts heating on giving it a target temperature.

When I let the bed thermistor remain in the SKR 2 and remove the bed heating wires from the heat bed control board, upon setting a target temperature for the bed, the printer does not restart but the bed temp not rises as the wires are removed.

I checked for any shortage between them and I found none. Also I can read the thermistor reading in Mainsail but it is fluctuating too much within the range of 1 degrees.

klippy (6).log (49.4 KB)

2

grafik
grafik1920×1356 420 KB 

[heater_bed]
heater_pin = PD7
sensor_type = Generic 3950
sensor_pin = PA3
control = pid
pid_kp = 22.2
pid_ki = 1.08
pid_kd = 114
min_temp = 0
max_temp = 130

Have you tried PA1 instead of PA3 (this is TH1)?

You also may check the thermistor pin for the extruder.

3

Hi shekharsuman,

I also use an SKR2, so I’m interested :wink:

I don’t understand your setup!

Could you please share some pictures? Block schematics?

I guess, it is some wrong ground connection, but…?

Kind regards, hcet14

1 Like
4

Initially…it was in PA1. I thought changing it might help. But it didn’t.

5

I’m using a SKR2 and RasPi4 as well and the config is

[heater_bed]
heater_pin: PD7
sensor_type: Generic 3950
sensor_pin: PA1

The temperature reading of the bed should not fluctuate that much. What printer are you using?
Maybe for a small test you can rewire the hotend to the bed outputs and change the config accordingly.
For me it looks like there is something wrong with the cabling or the bed heater port.
What resistance can be measured at the bed wires?

6

The bed thermistor and bed heater just don’t work together. I change thermistor, it doesn’t restart. I remove wires of bed, it doesn’t restart. Checked for continuity between thermistor and bed wires…found nothing.

7

Please give us more input.

8

Just wondering have you solved this problem? Because I have the same problem with my anycubic chiron. I flashed it to klipper and the problem shows. The heating bed works fine under marlin. But under klipper, whenever I want to heat the bed, it shows lost communication with mcu. I don’t know how to read the log.
Best regards.