Mellow Fly SB2040 Max V3 - help needed

[Tekdoc001]

Hello! I just installed a Mellow Fly SB2040 Max V3 on my Voron Trident and I can't seem to get klipper to use the eddy probe (although everything else including the probe temperature sensor seems OK). Klipper just shuts down with "MCU 'SB2040' shutdown: I2C Timeout" and I get  "Unable to obtain 'i2c_read_response' response" in the console when I try to calibrate the probe.

I am using the reference configuration from the Mellow web site for the eddy probe

[probe_eddy_current fly_eddy_probe]
sensor_type: ldc1612
i2c_address: 43
i2c_mcu: SB2040
i2c_bus: i2c1b
x_offset: 0     # remember to set x offset
y_offset: 21.42 # remember to set y offset
z_offset: 2     # remember to set z offset
i2c_speed: 4000000

I tried commenting out i2c_speed but it made no difference. @mvdveer, I read your unboxing post from 2024 so I know you have used this probe before. Any ideas on troubleshooting this? Thanks in advance for your help!

- Jonathan

 

Edited January 11 by Tekdoc001

[mvdveer]

3 hours ago, Tekdoc001 said:

I tried commenting out i2c_speed but it made no difference. @mvdveer, I read your unboxing post from 2024 so I know you have used this probe before. Any ideas on troubleshooting this? Thanks in advance for your help!

I got the probe but never used it as I switched all my printers to BEACON probes and using beacon touch. Had a quick look at the pinout and reference and it all seems spot on.  

All I can think off is a connection issue

I am off to work but will have a look later when I get home

[Tekdoc001]

Thanks for the reply. I have been looking through klipper commits on GitHub and I see there has been a lot of activity around the ldc1612 sensor and i2c since October 2024. I would not be surprised if one of those was a breaking change for this sensor/toolboard combo. If I could find someone who is/was using it successfully and find out which version of klipper they are/were using, that might point me in the right direction. I also have an email out to Mellow tech support and hopefully they will respond. Worst case scenario, I might try to return the V3 since I already have a V1 board that has been working great for a couple years now. I only bought the V3 to try the eddy probe but I could always just go back to the V1  and my slow inductive probe 

Edited January 11 by Tekdoc001

[polyneutron]

I had issues with can not with the probe but the carto. Pass through did not work. When I shared can from Manta klipper would loose the probe. Ebb36 worked well. Then Jabberwalky and Nighthawk everything is usb. No issues with nitehawk or carto using usb and usb passthrough. Nighthawk uses the usb passthough on the outside.

 

 

[polyneutron]

No issues with the mellow fly sht but carto didn't work with that board.

[Tekdoc001]

Thanks @polyneutron. I will save time/money by not trying to use another eddy probe via CAN with this toolboard.  But I don't want to reroute cables right now so that rules out a switch to USB 

[polyneutron]

One usb cable and a coaxial pass through all usb.

[Dmandn]

 

I had issues with mine until I set the SPI bus pins as per below:

[lis2dw]
cs_pin: SB2040:gpio12
spi_software_sclk_pin: SB2040:gpio2
spi_software_mosi_pin: SB2040:gpio3
spi_software_miso_pin: SB2040:gpio4
spi_bus:spi0_gpio4_gpio3_gpio2

 

Though might be unrelated for yours....does the v3 work without the probe config?

Edited January 12 by Dmandn

[Tekdoc001]

I have not tried the accelerometer yet @Dmandn but thanks, I will keep that in mind once I get around to testing it. For now, everything else (fans, heater, end stops, stepper, LEDs and thermistors - including the one on the eddy probe) is working but when I try to use the probe via the Mainsail console, klipper shuts down with that i2c error.

Edited January 12 by Tekdoc001

[mvdveer]

I just asked AI and got the following answer:

 

This error typically indicates a communication failure between the Klipper host (e.g., Raspberry Pi) and an I2C device on your 

Mellow Fly-SB2040 toolboard, such as an accelerometer (MPU6050) or temperature sensor (BME280). 

Immediate Troubleshooting Steps

• Verify Device Addresses: Ensure the I2C address in your printer.cfg matches your hardware. For example, some BME280 sensors use address 0x76 (118) instead of the common 0x77 (119).Check Physical Connections: I2C is sensitive to signal noise and capacitance.
• Inspect the toolboard connector for loose pins or bad crimps.
• Verify the CAN bus termination resistor (120 ohms) is correctly set if using CAN, as communication drops can trigger secondary I2C timeouts.
• Identify "Stuck" Devices: Use the i2cdetect utility to see if the device is visible on the bus. If it shows "UU", another driver has claimed it; if it shows nothing, the device is unresponsive. 

Configuration & Firmware Fixes

 

• Update Firmware: Reflash both your toolboard and the Klipper host software. Recent updates to the can2040 code and Klipper core have addressed intermittent communication timeouts.
• Increase Timeout Threshold: If the error occurs during high-load movements (like homing), you may need to increase the TRSYNC_TIMEOUT in the Klipper source code (though this requires manual modification of mcu.py).
• Reduce Bus Speed: If you have long cable runs, try reducing the I2C baud rate in your configuration to 100000 (100kHz) from the default 400000 (400kHz) to improve signal stability. 
• Common SB2040 Specific Issues
• Power Stability: Ensure your toolboard is receiving stable 24V power. Voltage drops or "crappy" USB/power cables can cause the MCU to brown out and drop I2C responses.
• TMC2240 Driver: If you are using the version of the board with a TMC2240, ensure the UART jumper is correctly installed, as incorrect driver communication can lead to system-wide MCU shutdowns. 

AI can make mistakes, so double-check responses

 

 

 

[Tekdoc001]

Thanks for the input everyone. I tried different klipper versions, swapping and reseating the flex cable, etc. and nothing worked. I have spent enough time on this, and the V3 is going back for a refund. And in case anyone is wondering, Mellow has still not responded to my inquiries on their Discord, Facebook group or by email.  I guess I got lucky with my V1 but I cannot see myself buying from Mellow in the future 

[polyneutron]

The pass through did not work v in relation to the eddy current probes. The ebb36 and ebb42 work well for can when you follow Esoteric's writ up for your board and probe. I was a little skeptical when jabberwocky had night hawk whisking is usb and come pre loaded with Kilipper. Connected the carto probe through usb pass through and carto software confirmed it. I zeroed the z axis as soon after the Manta m8p v2 lost motors 3, 4 and 5. Have a new Manta m8p V2 but the cm4 no longer wanted to go on line. The fan heat sink stopped working.