DevHeads IoT Integration Server•4w ago

How to Expand 10-Bit ADC Signal for 16-Bit SPI Communication Between Two Arduino Unos

hey guys I was working on a project previously where I needed to transmit a 10-bit signal from an analog/digital converter (ADC) to an Arduino Uno using the SPI protocol. Since SPI typically operates with a 16-bit data frame, I need to figure out how to pad or expand the 10-bit signal to fit into a 16-bit frame for transmission. To simulate the ADC, I plan to use a second Arduino Uno as an SPI Master, while the receiving Arduino would act as an SPI Slave. Unfortunately, I only have one Arduino at the moment, so I can’t test my setup yet. I’m also a bit unsure about how to correctly expand the 10-bit signal for SPI transmission. What improvements can be made to ensure reliable SPI communication between the Master and Slave? this is the code I’ve written for both the Master and Slave, but I could use some advice on how to implement the signal expansion and ensure proper communication between the two. Master Arduino Code:

#include <SPI.h>
#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 = 0b00001101;  // Simulating 10-bit signal
  byte y = 0b11111111;  // Need to figure out how to pad or expand this
  
  digitalWrite(SS, LOW);
  SPI.transfer(x);
  SPI.transfer(y);
  digitalWrite(SS, HIGH);

  delay(1000);
}

#include <SPI.h>
#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 = 0b00001101;  // Simulating 10-bit signal
  byte y = 0b11111111;  // Need to figure out how to pad or expand this
  
  digitalWrite(SS, LOW);
  SPI.transfer(x);
  SPI.transfer(y);
  digitalWrite(SS, HIGH);

  delay(1000);
}

Slave Arduino Code:

#include <SPI.h>
#define SS 10
#define MOSI 11

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

void loop() {
  byte x = SPDR;
  byte y = SPDR;
  
  Serial.print(x, DEC);  // Converting received data to decimal
  Serial.print(y, DEC);

  delay(1000);
}

#include <SPI.h>
#define SS 10
#define MOSI 11

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

void loop() {
  byte x = SPDR;
  byte y = SPDR;
  
  Serial.print(x, DEC);  // Converting received data to decimal
  Serial.print(y, DEC);

  delay(1000);
}

Is there a way to test this code without a second Arduino, or can I simulate the SPI communication in some other way?

1 Reply

Alien Queen•4w ago

To transmit a 10-bit signal from one Arduino to another using SPI, you need to expand the 10-bit signal to fit into a 16-bit frame. Signal Expansion - Pack the 10-bit Signal: Shift the 10-bit value left by 6 bits to create space for padding.

   uint16_t expandedSignal = (x << 6);

   uint16_t expandedSignal = (x << 6);

- Split for Transmission: Extract the high and low bytes.

   byte highByte = (expandedSignal >> 8) & 0xFF;
   byte lowByte = expandedSignal & 0xFF;

   byte highByte = (expandedSignal >> 8) & 0xFF;
   byte lowByte = expandedSignal & 0xFF;

Updated Master Code Send the two bytes:

digitalWrite(SS, LOW);
SPI.transfer(highByte);
SPI.transfer(lowByte);
digitalWrite(SS, HIGH);

digitalWrite(SS, LOW);
SPI.transfer(highByte);
SPI.transfer(lowByte);
digitalWrite(SS, HIGH);

Reconstruct the original signal:

uint16_t receivedSignal = (receivedHighByte << 8) | receivedLowByte;
uint16_t originalSignal = receivedSignal >> 6; // Retrieve the original 10-bit signal

uint16_t receivedSignal = (receivedHighByte << 8) | receivedLowByte;
uint16_t originalSignal = receivedSignal >> 6; // Retrieve the original 10-bit signal

Testing Without a Second Arduino You can simulate SPI by connecting the MOSI pin of the master to the MISO pin of the slave, allowing for loopback testing. - Ensure correct connections (MOSI, MISO, SCK, SS). - Pay attention to timing with appropriate delays. - Consider pull-up resistors for the SS line. - Use serial prints for debugging data transmission.

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How to Expand 10-Bit ADC Signal for 16-Bit SPI Communication Between Two Arduino Unos