Transfer 10-bit via Arduino-to-Arduino SPI protocol The task I need to accomplish is as follows:

I have an analog/digital converter that sends out a 10-bit signal. This signal needs to be transferred to an Arduino Uno using the SPI protocol. Because the SPI protocol works with a 16 bit pattern I need to expand the incoming signal. The slave Arduino then needs to put out the transferred number in decimal.

I imitated the ADC with another Arduino Uno, setting it as master, but unfortunately at the time I only had one Arduino so I couldn't test my code. Furthermore, I don't really have a clue how to "expand" a 10-bit signal to a 16-bit one. Can someone please explain it to me and have a look at my code?

Code for the master Arduino:

#include &lt;SPI.h&gt;
#define SS 10
#define MOSI 11

void setup() {
  pinMode(SS, OUTPUT);
  pinMode(MOSI, OUTPUT);
  SPI.beginTransaction(SPISettings(62500, LSBFIRST, SPI_MODE0));
}

void loop() {
  byte x=0000001101;
  byte y=0011111111;
  digitalWrite(SS,LOW);
  SPI.transfer(x,y);
  digitalWrite(SS,HIGH);
  delay(1000);
}


Code for the slave Arduino:

#include &lt;SPI.h&gt;
#define SS 10
#define MOSI 11

void setup() {
  pinMode(SS, INPUT);
  pinMode(MOSI, INPUT);
}

void loop() {
  byte x=SPDR;
  byte y=SPDR;
  printf(x,DEC);
  printf(y,DEC);
  delay(1000);
}
A byte is only 8 bits, so your code:

  byte x=0000001101;
  byte y=0011111111;


won't do what you think it does.

A 10 bit value will be stored as an int (which is 16 bits) or 2 bytes.

Assuming it is an int then this will convert it to two bytes.

 const int adcData = 0x03FF;  // From ADC
 byte dataToSend[2] = {0, 0}; // Initialise it to zeros
 dataToSend[0] = (adcData &amp; 0xFF00) &gt;&gt; 8;  // didn't really need the bit mask just to make it clearer.
 dataToSend[1] = (adcData &amp; 0x00FF);
 // Now send dataToSend via the SPI bus.


To reassemble the data on the otherside:

 byte dataReadFromSPI[2];  // Filled with the data read from the SPI
 int adcData = 0;
 adcData = (dataReadFromSPI[0] &lt;&lt; 8) | (dataReadFromSPI[1]);