Installing BDsensor-m

Connect the sensor cable to the EXP1 interface on the mainboard

If the sensor cable is not long enough, you can use the extension cable included in the package
The CLK and SDA wires of the BDsensor-m can be connected to any GPIO pin on the 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) 

Since some pins in the mainboard connectors may not be directly connected to the MCU's GPIO (for example, they may have filter capacitors on them or be isolated through MOSFETs, diodes, or optocouplers, but they can also be used if they are isolated through resistors or resistor pull-ups/pull-downs), they cannot be used with the BDsensor-m. And the firmware will report a connection error. For example
Fan and heater connectors are isolated through MOSFETs,
The connectors used for temperature thermistors and limit/probe switches on some boards are usually connected to GND through filter capacitors,

As shown in the figure below, install the BD sensor near the hotend. STL of mount, STL_mount_VzBot_Goliath short

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Installing the Patch into Marlin Firmware

The BDsensor has been integrated into Marlin 2.1.x (since 2022.8.27),

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

What you need is to 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
Homing with the probe

Make sure 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 homing bump speed and the Z-axis homing speed, because the limit signal read from the BDsensor-m is not as real-time as a normal limit switch.

Edit Configuration_adv.h

#define BABYSTEPPING Enable this feature 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 SDA and SCL pins 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 auto bed leveling probing (G29) before printing like a normal BLTouch, uncomment

#define AUTO_BED_LEVELING_BILINEAR

and edit 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

Displaying BD Sensor Values on the LCD Screen

For printers with status display (supporting gcode M117), such as LCD12864 or some UART screens, like ender3V2 ...

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 0 point, so no z_offset is needed; we set the value to 0).
Send the gcode command M102 S-6. The printer will slowly move the Z-axis upward 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 whether the BD sensor has been successfully calibrated. This will return the raw calibration data stored in the BD sensor.

There is also a calibration tool that can 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 that it is outside the sensor range. If the first 5 points (0~0.5mm) or more have values within the range of 0 to 1000, and the delta of the increasing values is >=10, it means the calibration is successful. Just like the chart shown 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 make sure that the second data value is greater than the first data value by more than 10.

Testing and Printing

Menu: Bed Leveling

Auto Bed Leveling

There are two methods to automatically level the bed:

1. Use M102 for real-time leveling of the first few layers

We can easily enable or disable this auto-leveling function by sending a gcode command or adding gcode to the gcode file.

To enable bed leveling in Cura, add the M102 code directly below the G28 (home all axes) code in the "Start G-code" section of the printer machine settings. For example, below G28, this means bed leveling is only performed when the Z-axis height does not exceed 0.2mm. M102 S2

Send M102 S0 to disable real-time leveling of the BD sensor (G28, M18 will also disable it). By the way, this function is disabled by default.

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 automatic bed leveling method is like BLtouch's G29, just add a line of G29 below G28.

Installation Video

Installation video by Chris's Basement

Check Z endstop `M119`

Before checking this step, do not home Z, otherwise the nozzle may hit the printer bed.

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

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

If z min is not triggered, please check your configuration. #define Z_MIN_ENDSTOP_HIT_STATE HIGH

Make sure the Z motor is off/unlocked
Move the Z axis down by hand until the nozzle touches the bed surface
Send M102 S-2, the return value should be 0.00mm, then send M119 again, and you can see that the z endstop is now triggered.

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

Check connection

Check the connection via M102 S-1. This is an example of the return message. If it returns blank or another string, please check the connection and wire order.

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

Connect the sensor cable to the EXP1 interface on the mainboard​

Installing the Patch into Marlin Firmware​

Edit Configuration.h​

Edit Configuration_adv.h​

Edit pins_boardname.h​

Displaying BD Sensor Values on the LCD Screen​

Calibration​

Testing and Printing​

There are two methods to automatically level the bed:​

Check Z endstop M119​

Check connection​

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