This page describes the result of measurements, which pin is connected to where.
There is online not much information available about the ChiTu F X board. The following pdf is what I collected from a search through the internet:
List of components:
Connection diagram ChiTu F X series V4.3 191205-FX U8 IC:STM32F446ZET6, LQFP 144 pin 54 PF14 -> U6_E1,P.2 (E1-EN) 47 PB1 -> U6_E1,P.16 (E1-STP) 53 PF13 -> U6_E1,P.19 (E1-DIR) 89 PG4 -> U6_E2,P.2 (E2-EN) 82 PD13 -> U6_E2,P.16 (E2-STP) 90 PG5 -> U6_E2,P.19 (E2-DIR) 10 PF0 -> U6_X,P.2 (X-EN) 04 PE5 -> U6_X,P.16 (X-STP) 11 PF1 -> U6_X,P.19 (X-DIR) 15 PF5 -> U6_Y,P.2 (Y-EN) 21 PF9 -> U6_Y,P.16 (Y-STP) 13 PF3 -> U6_Y,P.19 (Y-DIR) 41 PA5 -> U6_Z,P.2 (Z-EN) 42 PA6 -> U6_Z,P.16 (Z-STP) 55 PF15 -> U6_Z,P.19 (Z-DIR) 93 PG8 -> Q5,P.G (E1_HOT) 110 PA15 -> Q20,P.G (E2_HOT) U6_E1 IC:TMC2209-LA 01 OB2 (E1-MOTOR,P.2B) 02 ENN (U8,P.54/PF14) 03 GND 04 CPO 05 CPI 06 VCP 07 SPREAD 08 5VOUT 09 MS1_AD0 10 MS2_AD1 11 DIAG 12 INDEX 13 CLK 14 PDN_UART 15 VCC_IO 16 STEP (U8,P.47/PB1) 17 VREF 18 GND 19 DIR (U8,P.53/PF13) 20 STDBY 21 OA2 (E1-MOTOR,P.1B) 22 VS 23 BRA 24 OA1 (E1-MOTOR,P.1A) 25 . 26 OB1 (E1-MOTOR,P.2A) 27 BRB 28 VS U6_E2 IC:TMC2209-LA 01 OB2 (E2/EXT-MOTOR,P.2B) 02 ENN (U8,P.89/PG4) 03 GND 04 CPO 05 CPI 06 VCP 07 SPREAD 08 5VOUT 09 MS1_AD0 10 MS2_AD1 11 DIAG 12 INDEX 13 CLK 14 PDN_UART 15 VCC_IO 16 STEP (U8,P.82/PD13) 17 VREF 18 GND 19 DIR (U8,P.90/PG5) 20 STDBY 21 OA2 (E2/EXT-MOTOR,P.1B) 22 VS 23 BRA 24 OA1 (E2/EXT-MOTOR,P.1A) 25 . 26 OB1 (E2/EXT-MOTOR,P.2A) 27 BRB 28 VS U6_X IC:TMC2209-LA 01 OB2 (X-MOTOR,P.2B) 02 ENN (U8,P.10/PF0) 03 GND 04 CPO 05 CPI 06 VCP 07 SPREAD 08 5VOUT 09 MS1_AD0 10 MS2_AD1 11 DIAG 12 INDEX 13 CLK 14 PDN_UART 15 VCC_IO 16 STEP (U8,P.04/PE5) 17 VREF 18 GND 19 DIR (U8,P.11/PF1) 20 STDBY 21 OA2 (X-MOTOR,P.1B) 22 VS 23 BRA 24 OA1 (X-MOTOR,P.1A) 25 . 26 OB1 (X-MOTOR,P.2A) 27 BRB 28 VS U6_Y IC:TMC2209-LA 01 OB2 (Y-MOTOR,P.2B) 02 ENN (U8,P.15/PF5) 03 GND 04 CPO 05 CPI 06 VCP 07 SPREAD 08 5VOUT 09 MS1_AD0 10 MS2_AD1 11 DIAG 12 INDEX 13 CLK 14 PDN_UART 15 VCC_IO 16 STEP (U8,P.21/PF9) 17 VREF 18 GND 19 DIR (U8,P.13/PF3) 20 STDBY 21 OA2 (Y-MOTOR,P.1B) 22 VS 23 BRA 24 OA1 (Y-MOTOR,P.1A) 25 . 26 OB1 (Y-MOTOR,P.2A) 27 BRB 28 VS U6_Z IC:TMC2209-LA 01 OB2 (Z-MOTOR,P.2B) 02 ENN (U8,P.41/PA5) 03 GND 04 CPO 05 CPI 06 VCP 07 SPREAD 08 5VOUT 09 MS1_AD0 10 MS2_AD1 11 DIAG 12 INDEX 13 CLK 14 PDN_UART 15 VCC_IO 16 STEP (U8,P.42/PA6) 17 VREF 18 GND 19 DIR (U8,P.55/PF15) 20 STDBY 21 OA2 (Z-MOTOR,P.1B) 22 VS 23 BRA 24 OA1 (Z-MOTOR,P.1A) 25 . 26 OB1 (Z-MOTOR,P.2A) 27 BRB 28 VS E1-MOTOR J:4 pin JST conn 1B U6-E1,P.21 1A U6-E1,P.24 2A U6-E1,P.26 2B U6-E1,P.1 E2/EXT-MOTOR J:4 pin JST conn 1B U6-E2,P.21 1A U6-E2,P.24 2A U6-E2,P.26 2B U6-E2,P.1 X-MOTOR J:4 pin JST conn 1B U6-X,P.21 1A U6-X,P.24 2A U6-X,P.26 2B U6-X,P.1 Y-MOTOR J:4 pin JST conn 1B U6-Y,P.21 1A U6-Y,P.24 2A U6-Y,P.26 2B U6-Y,P.1 Z-MOTOR J:4 pin JST conn 1B U6-Z,P.21 1A U6-Z,P.24 2A U6-Z,P.26 2B U6-Z,P.1 E1_HOT J:2-pin screw terminal 5.08mm E1 GND HOT <- Q5,P.D E2_HOT J:2-pin screw terminal 5.08mm E2 GND HOT Q5 TR:WSF40N06, N-Ch. Mosfet (60v, 20mOhm, 50A) G <- R42,P.1 + U8,P.93 (PG8) D -> E1_HOT,P.HOT S <- +12/24V R42 R:01C (10k, 1%) 1 Q5,P.G 2 GND Q20 TR:WSF40N06, N-Ch. Mosfet (60v, 20mOhm, 50A) G <- R21,P.1 + U8,P.110 (PA15) D -> E2_HOT,P.HOT S <- +12/24V R21 R:01C (10k, 1%) 1 Q20,P.G 2 GND
Below is the pinout from the FPC cable (FPC-350C40119V1)
Connector U4
1 VCC (+3.3v) 2 VCC (+3.3v) 3 VCC (+3.3v) 4 5 6 GND 7 GND 8 GND 9 10 11 12 13 XPT2046,P.16 (DCLK) 14 XPT2046,P.15 (_CS) 15 XPT2046,P.14 (DIN) 16 XPT2046,P.12 (DOUT) 17 XPT2046,P.11 (_PENIRQ) 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 GND 37 38 39 40 VCC (+3.3v)