Installing BDsensor-m-m

Connect the sensor cable to the EXP1 port of the mainboard

If the sensor cable length is insufficient, the extension cable included in the package can be used.
The CKL and SDA wires of the BDsensor-m-m can be connected to any GPIO pins on the circuit board. You can also connect the BD sensor cable directly to the Bltouch port, for example:

BLtouch    |    BDsensor-m
5V       -->     5V
GND      -->     GND
S        -->     CLK/SCL    (Input)
GND      -->     GND
Zmin     -->     SDA    (Input/Output) 

Some pins in the motherboard connector may not be directly connected to the MCU's gpios (e.g., they may have filter capacitors or be isolated via MOSFETs, diodes, or optocouplers; but if they are isolated through resistors or resistor pull-ups/pull-downs, it is also acceptable). Therefore, they cannot be used with BDsensor-m, and the firmware will report a connection error. For example:
The connectors for fans and heaters are isolated via MOSFETs.
In some boards, the connectors for temperature thermistors and endstops/probes are often connected to GND via filter capacitors.

Install the BD sensor close to the hotend as shown in the figure below. STL of mount, STL_mount_VzBot_Goliath short

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Install the patch into Marlin firmware

The BD sensor has been integrated into Marlin 2.1.x (since 2022.8.27).

You can download the release version. However, it is now recommended to download the latest bugfix version: https://github.com/MarlinFirmware/Marlin

What you need to do is modify the configuration files and pin files.

Edit Configuration.h

Enable BD_SENSOR

Uncomment
```
#define BD_SENSOR`
#define Z_SAFE_HOMING
#define BD_SENSOR_PROBE_NO_STOP //adding this new line for fast bed leveling without nozzle stop, 
```
Only BD_SENSOR_PROBE_NO_STOP

Latest Marlin bugfix: https://github.com/MarlinFirmware/Marlin

Description: https://github.com/MarlinFirmware/Marlin/pull/25847
Use probe for homing

Ensure Z_MIN_PROBE_USES_Z_MIN_ENDSTOP_PIN is disabled, and USE_PROBE_FOR_Z_HOMING should be enabled as shown below:
```
//#define Z_MIN_PROBE_USES_Z_MIN_ENDSTOP_PIN
// Force the use of the probe for Z-axis homing
#define USE_PROBE_FOR_Z_HOMING
```
Slow down the second homing Z speed
```
#define Z_PROBE_FEEDRATE_SLOW (Z_PROBE_FEEDRATE_FAST / 16)
```
Here, we must slow down the bump homing speed and Z homing speed because the stopper reading from the BDsensor-m process is not real-time like a normal stopper.

Edit Configuration_adv.h

#define BABYSTEPPING Enable this to achieve real-time leveling functionality.
```
#define HOMING_BUMP_DIVISOR { 2, 2, 8 }       // Re-Bump Speed Divisor (Divides the Homing Feedrate)
```

Edit pins_boardname.h

Configure the pins for the SDA and SCL of the BDsensor-m in the pin file pins_boardname.h (e.g., pins_PANDA_PI_V29.h) by adding the following 3 lines:

#define  I2C_BD_SDA_PIN    PC6   // Please change to the actual number which the SDA wire is connected to your mainboard
#define  I2C_BD_SCL_PIN    PB2   // Please change to the actual number which the SLK wire is connected to your mainboard
#define  I2C_BD_DELAY  20      // default value is 20, should be in the range [20,50].

If you want to perform automatic bed leveling probing (G29) before printing, like with a normal BLtouch, uncomment

#define AUTO_BED_LEVELING_BILINEAR

And set the values as shown below:

#define Z_CLEARANCE_DEPLOY_PROBE   0 // Z Clearance for Deploy/Stow
#define Z_CLEARANCE_BETWEEN_PROBES  1 // Z Clearance between probe points
#define Z_CLEARANCE_MULTI_PROBE     1 // Z Clearance between multiple probes

Display BD sensor value on the LCD screen

Applicable for printers with status display (supporting gcode M117), such as LCD12864 or some uart screens like the Ender 3 V2...

Calibration

Clean the nozzle, then move the Z axis via the console until the nozzle just touches the bed (BDsensor-m will use this position as the zero point, so z_offset is not needed; set the value to 0).
Send the gcode command M102 S-6. The printer will slowly move the Z axis up by 0.1mm each time until it reaches 4mm. Do not run M102 S-6 before installing the sensor, and do not turn off the printer power during calibration, otherwise the old calibration data will be deleted. If this happens, simply calibrate again.
You can send M102 S-5 to check if the BD sensor has been calibrated successfully. This will return the raw calibration data stored in the BD sensor.

A calibration tool is also available to do this: https://github.com/markniu/Bed_Distance_sensor/raw/new/marlin/BD_Config_Tool_Marlin.zip

Note: A data value of 1015 or > 1010 indicates the value is out of the sensor range. If the first 5 points (0~0.5mm) or more values are within the range of 0 to 1000, and the delta of the increasing values is >= 10, it means the calibration is successful, as shown in the chart above.

If the first raw calibration data returned by M102 S-5 is greater than 400, it means the sensor is installed too high and needs to be reinstalled closer to the bed. Also ensure the second data value is more than 10 greater than the first.

Testing and Printing

Menu Bed Leveling

Auto Bed Leveling

There are two methods for automatic bed leveling:

1. Real-time leveling for the first few layers using M102

We can easily enable or disable this automatic leveling by sending gcode commands or adding gcode commands to the gcode file.

To enable bed leveling in Cura, add the M102 S4 gcode command right below the G28 (home all axes) gcode command in the "Start G-code" section of the printer machine settings. For example, below G28, this means it will only perform bed leveling below a Z-axis height of 0.2mm. M102 S2

Send to disable the BD sensor bed leveling (disabled by default). M102 S0``G28``M18

M102   S-1     //Read sensor information, and we can use this for connection checking.
M102   S-2     //Read current distance value
M102   S-5     //Read raw Calibrate data
M102   S-6     //Start Calibrate,before that make sure the nozzle is just touched the bed,and then the printer restarted. don't home z axis before this.
M102   S4      //Set the adjustable Z height value,e.g. M102 S4  means it will do adjusting while the Z height <=0.4mm , disable it by M102 S0.

2. G29 automatic bed leveling

Another method for automatic bed leveling is like using G29 with BLtouch. Simply add the line G29 below G28.

Installation Video

Installation Video by Chris Basement

Check Z endstop `M119`

Do not home Z before checking this step, otherwise the nozzle may crash into the printer bed.

This is the return message after sending the M119 command (reports endstop status).

Send: M119
Recv: x:open y:open z:open

If z min is not open, check your configuration. #define Z_MAX_ENDSTOP_HIT_STATE HIGH

Ensure the Z motor is disabled/unlocked.
Manually move the Z axis down until the nozzle is close to the bed.
Send M102 S-2. The return value should be 0.00mm. Then send M119 again. You should see that the z endstop is now triggered.

Send: M119
Recv: x:open y:open z:TRIGGERED

Check Connection

Check the connection using M102 S-1. Below is an example of the returned message. Check if the connection and wire order return a blank or another string.

Send: M102 S-1
Recv: V1.0 pandapi3d.com

Connect the sensor cable to the EXP1 port of the mainboard​

Install the patch into Marlin firmware​

Edit Configuration.h​

Edit Configuration_adv.h​

Edit pins_boardname.h​

Display BD sensor value on the LCD screen​

Calibration​

Testing and Printing​

There are two methods for automatic bed leveling:​

Check Z endstop M119​

Check Connection​

If all the above steps are correct, you can now home the z axis.​