What do I need to configure to get Marlin to run an Ender 3 Pro with CR Touch?

Question

I have an Ender 3 Pro, board version 4.2.2, and a CR Touch with 5 pin connector. I also removed the z-axis endstop connector at the endstop.

I've been building and flashing Marlin 2.1.2.2, but I haven't found a configuration that makes the CRTouch work as expected. Typically, during auto homing, the machine will ignore the probe triggering and drive Z into the bed either 100% of the time or most of the time. I didn't take detailed enough notes to know for sure.

As a test case, I tried following along with this answer exactly and still had the same problem. Configuration changes from the Marlin Ender 3 Pro default:

• Z_MIN_PROBE_USES_Z_MIN_ENDSTOP_PIN commented out
• USE_PROBE_FOR_Z_HOMING uncommented
• Z_MIN_PROBE_PIN uncommented and set to PB1
• BLTOUCH uncommented
• NOZZLE_TO_PROBE_OFFSET set to { -44, -9, -0.9 } (here I differ slightly from the { -44, -9, 0 } in the answer)
• AUTO_BED_LEVELING_UBL uncommented
• ENABLE_LEVELING_AFTER_G28 uncommented
• Z_SAFE_HOMING uncommented (not in the answer, but in a comment)

On my first boot after inserting the SD card with firmware:

1. The probe deployed and retracted a couple of times, ending retracted with the red LED on
2. The machine seemingly flashed the firmware as it sat on a blue screen for a while
3. The CRTouch LED turned purple I think when flashing ended, though I can't tell from my video
4. When I got to the main menu, I started auto homing
5. X and Y axes worked as expected
6. For the Z axis, the probe centered on the build plate, deployed, and the LED turned blue
7. The probe started lowering, contacted the plate and retracted. The LED turned to blinking red, maybe steady red first. The Z motor kept driving down so I killed the power

The extruder fan also made a loud buzzing noise that gradually grew quieter. In the past I've noticed the buzzing seemingly get quieter when the probe is deployed or retracted.

Anyone know what could be causing this, or how to troubleshoot it? Creality's firmware works as expected, so it's not a hardware problem. I was thinking maybe PB1 is wrong for the Ender 3 Pro, but from what I see online I gather it's the same mainboard between both printers.

Answer 1

I think this is an issue with Marlin v2.1.2.2, which I was trying to use. https://github.com/MarlinFirmware/Marlin/issues/26809 this issue points to another bug with probing. My issue is different, but downgrading to 2.1.1 solved it.

Answer 2

I also have an ender 3 pro that I added a bl touch to. I set mine up with removing the z limit switch and connecting the bl touch using those pins along with the z probe pins. You need to verify which board you have (probably a v4.2.2) and which cpu is on your board,mine was STM32F103 RET6 CPU there are some using a different model. I was never able to get marlin to build and work with the bl touch, however I was able to flash https://github.com/zisismaras/ender_3_4.2.2_firmware which worked fine. A 4.2.2 board with the RET6 cpu is required. You / someone could do a config side by side and figure out which flag(s) you are missing in your configuration or you could just flash whichever probe grid you are comfortable with and use these auto builds.

Answer 3

I know this issue was a long time ago but the answer is still relevant. When compiling Marlin yourself it is actually quite simple with just a few enables to get a BL/CR Touch to work.

1. Enable #define USE_PROBE_FOR_Z_HOMING
2. Enable #define BLTOUCH

This is all that you need for the probe to function as long as your proper board is defined as auto-build Marlin will take care of all the rest. This is of course applicable if using the 5-pin probe port.

Things to consider that will stop Z from going negative are:

1. #define Z_PROBE_LOW_POINT — if set to high, the probe will not function properly and more then likely fail a level bed probe.

2. //#define MIN_SOFTWARE_ENDSTOP_Z — This is a built-in safety feature that will stop the probe dead in its tracks if not commented out.

Between these two the probe will never reach the bed or fail at many spots because the probe point is lower then specified.

In advanced config.h, there are BLTouch settings for high-speed probing. No other probe is capable of these features, except for an original ANTCLABS BLTouch. Using these for other probes will cause erratic behavior and bed probe failure.

Using the BTT mini probe your GND and SIG out pins have to be place on the Z stop pin instead because the mini probe requires a strong pull-up on the signal line which as of now the 5-pin probe port does not have. When you use the Z endstop uncomment out the following line- #define Z_MIN_PROBE_USES_Z_MIN_ENDSTOP_PIN.

Also, remember V1 mini probe uses a high signal and V2 uses a low signal but they still require a pull-up on the signal line as well and can be enabled in Marlin as well. #define ENDSTOPPULLUP_ZMIN_PROBE.

Your pin files Marlin uses will not have to be modified as long as your proper board is defined. Remember Auto Build Marlin is your friend.