MCU : STM32F103VET6 (Master & Slave) STM32 Cube MX : 6.12.0 Firmware package version : 1.8.6 Master MCU configure- Receive only Master- NSS : Disable ( However, different GPIO sent a signal for the slave NSS )- Clock 72 Mhz - SPI Prescaler:  4 (9.0 M...