Connections for Maker NANO are shown above

You can now type in the code for the Master ( The Blue Pill ) into your Arduino IDE

#include<SPI.h>

// Define Constants and Variables

#define SS PA4

#define led PC13

unsigned char MasterSend;;

unsigned char MasterReceive;

void setup() {

pinMode(led,OUTPUT);

Serial.begin(115200);

// SPI Init

SPI.begin();

SPI.setClockDivider(SPI_CLOCK_DIV16);

digitalWrite(SS,HIGH); // set as master

MasterSend = 0xFF;

}

void loop() {

Serial.print("Sent to Slave ");

Serial.print(" [0x");

Serial.println(MasterSend,HEX);

MasterReceive = SPI.transfer(MasterSend);

Serial.print("Received from Slave ");

Serial.print(" [0x");

Serial.print(MasterReceive,HEX);

Serial.println("]");

digitalWrite(led,!digitalRead(led));

delay(200);

}

And in ANOTHER INSTANCE of the Arduino IDE, the code for the SLAVE (Maker NANO)

//SPI Slave Code for Arduino

//SPI Communication between STM32F103C8 & Arduino

#include<SPI.h>

volatile boolean received;

volatile unsigned char SlaveReceived;

volatile unsigned char SlaveSend;

void setup()

{

Serial.begin(115200);

pinMode(MISO,OUTPUT);

SPCR |= _BV(SPE);

received = false;

SPI.attachInterrupt();

SlaveSend = 0xAA;

}

ISR(SPI_STC_vect)

{

SlaveReceived = SPDR;

received = true;

}

void loop() {

Serial.print("Received from Master");

Serial.print(" [0x");

Serial.print(SlaveReceived,HEX);

Serial.println("] ");

SPDR = SlaveSend;

Serial.print("Sent to Master");

Serial.print(" [0x");

Serial.print(SlaveSend,HEX);

Serial.println("]");

delay(200);

}

Upload the code to the boards, and open the serial monitors on both instances of the Arduino IDE.
Set the Baud Rate to 115200
You will see that the Master sends a byte to the Slave, and the Save replies with a byte of it's own.

Master sends data to Slave, Receives Data Back

Slave received data from Master, and replies with data of its own