2 Teensy 3.5, SPI Master/Slave Communication

Gripporillat · May 1, 2020

Hi everybody!

I'm experimenting with SPI and trying to make two Teensy 3.5 communicate with each other. Im using the tonton81's TSPISlave library. But somehow I just can't make it work.

This is my wiring:

Master -> Slave
Vin Vin
GND GND
10 10
11 12
12 11
13 13

Master Code:

Code:

#include <SPI.h>  // include the SPI library:

uint8_t zero = 0;
const int slaveSelectPin = 10;

void setup() {
  Serial.begin(115200);
  delay(1000);
  // set the slaveSelectPin as an output:
  pinMode (slaveSelectPin, OUTPUT);
  // initialize SPI:
  SPI.begin(); 
}

void loop() {
  receiveShit();
  delay(1000);
}

int receiveShit() {
  uint8_t data;
  // take the SS pin low to select the chip:
  digitalWrite(slaveSelectPin,LOW);
  //  send in the address and value via SPI:
  data = SPI.transfer(zero);
  // take the SS pin high to de-select the chip:
  digitalWrite(slaveSelectPin,HIGH); 
  Serial.println(data);
}

Slave Code:

Code:

#include "TSPISlave.h"

uint8_t miso = 12;
uint8_t mosi = 11;
uint8_t sck = 13;
uint8_t cs = 10;
uint8_t spimode = 8;
uint8_t counter = 0;

TSPISlave mySPI = TSPISlave(SPI, miso, mosi, sck, cs, spimode);

void setup() {
  mySPI.onReceive(myFunc);
}

void loop() {
}

void myFunc() {
  while ( mySPI.active() ) {
    if (mySPI.available()) {
      

      
      mySPI.pushr(counter);
      if (counter == 255) {
        counter = 0;
      } else {
        counter = counter++;
      }
    }
  }
}

The only output I get is "0". Any help would be highly appreciated.

Thanks in advance!

Gripporillat · May 1, 2020

I've changed the code and now it works... kind of. The master receives increasing values but somehow most of them are missing. As seen here:

New master code:

Code:

#include <SPI.h>  // include the SPI library:
uint8_t counter = 0;
uint8_t zero = 0;
const int slaveSelectPin = 10;

void setup() {
  Serial.begin(115200);
  delay(1000);
  // set the slaveSelectPin as an output:
  pinMode (slaveSelectPin, OUTPUT);
  // initialize SPI:
  SPI.begin(); 
  SPI.beginTransaction(SPISettings(2000000, MSBFIRST, SPI_MODE0));
}

void loop() {
  receiveShit();
}

int receiveShit() {
  uint8_t data;
  // take the SS pin low to select the chip:
  digitalWrite(slaveSelectPin,LOW);
  
  //  send in the address and value via SPI:
  data = SPI.transfer(zero);
  // take the SS pin high to de-select the chip:
  digitalWrite(slaveSelectPin,HIGH); 
  Serial.print(data);
  Serial.print(" .. ");
  counter = counter + 1;
  if (counter == 19) {
    Serial.println("");
    counter = 0;
  }
}

New slave code:

Code:

#include "TSPISlave.h"

uint8_t miso = 12;
uint8_t mosi = 11;
uint8_t sck = 13;
uint8_t cs = 10;
uint8_t spimode = 8;
  uint8_t counter = 0;


TSPISlave mySPI = TSPISlave(SPI, miso, mosi, sck, cs, spimode);

void setup() {
  

  mySPI.onReceive(myFunc);
  
} 

void loop() {
  
}

void myFunc() {
  while ( mySPI.active() ) {
    if (mySPI.available()) {
      mySPI.pushr(counter);
      
      if (counter == 255) {
        counter = 0;
      } else {
        counter = counter+1;
      }
      
    }
  }

}

Edit: The higher the baud rate the less values get skipped. This is with 20 Mhz:

I don't understand it at all

2 Teensy 3.5, SPI Master/Slave Communication

Gripporillat

Well-known member

Gripporillat

Well-known member