NucleoF401RE（Slave）のADC結果をSPIでArduino（Master）に送信する

まだ動いていない
Nucleoのコード

 // Reply to a SPI master as slave
 
 #include "mbed.h"
 
 SPISlave device(PA_7, PA_6, PA_5, PA_4); // mosi, miso, sclk, ssel
Serial pc(SERIAL_TX, SERIAL_RX);
 
 int main() {
     device.reply(0x03);              // Prime SPI with first reply
     while(1) {
         if(device.receive()) {
            pc.printf("data received.\n");
             int v = 2000;   // Read byte from master
             uint8_t hbyte = v / 256;
             uint8_t lbyte = v % 256;
             wait(0.002);
             device.reply(hbyte);         // Make this the next reply
             wait(0.002);
             device.reply(lbyte);         // Make this the next reply
         }
     }
 }

この辺とかかな
https://developer.mbed.org/forum/ja/topic/27018/