Overview
BigTreeTech released the BTT-MOT-EXP. It is an adapter that would ordinarily allow 3 more extra drivers to be added to an SKR v2.0.
Connecting the boards
Connect two 10-pin IDC cables between EXP1 and EXP2 on the SKR v2.0 and EXP1 and EXP2 on the BTT EXP-MOT V1.0.
12/24v power should be connected to the BTT-MOT-EXP to power the drivers.
If using the drivers in UART mode, a jumper should be added to the pins underneath the driver as normal.
SKR3 H743 Board.txt configuration
Please edit the stepper.numSmartDrivers in the board.txt file to 8 (assuming you have TMC2208, TMC2009, TMC2225, TMC2226 or TMC5160 drivers in all other sockets).
stepper.numSmartDrivers = 8
Please add the following lines to the board.txt.
stepper.enablePins = { PD_6, PD_1, PE_0, PC_7, PD_13, PC_4, PE_12, PE_11 }
stepper.stepPins = { PD_4, PA_15, PE_2, PD_15, PD_11, PA_7, PE_7, PA_6 }
stepper.directionPins = { PD_3, PA_8, PE_3, PD_14, PD_10, PB_2, PA_4, PA_5 }
stepper.TmcUartPins = { PD_5, PD_0, PE_1, PC_6, PD_12, PE_10, PE_8, PB_0 }
Sensorless Homing
Supported by only the TMC2209, TMC2226 and TMC5160 If using sensorless homing/stall detection on the BTT-MOT-EXP with TMC2209 or TMC2226 the following line must be added to the board.txt file. It is not needed with TMC5160.
stepper.TmcDiagPins = { PC_1, PC_3, PC_0, PC_2, PA_0, PE_9, PB_1, PC_5 }
Please only include the diag pin numbers where you intend to use sensorless homing on that axis.
For example, if you only intend to use sensorless homing/stall detection on driver 0 and driver 1, only include PF_2 and PC_13 in your board.txt file.
For more information about setting up sensorless homing, please read this.
Config.g Modification
The three added drivers would become driver 5, driver 6 and driver 7.
e.g.
M569 P5 S0
M569 P6 S0
M569 P7 S0