i2c AND spi do not work together

@henrik_t7 We need a lot more info. What exactly is happening or not happening?

@henrik_t7 I do see one thing but don't know if it's the problem. You are opening and closing the SD card every pass through the loop. Unless you have a high wear card, that will destroy the card quickly. 

It's a tricky problem with continuous loop applications. Using an SD card as storage is also problematic. If you want reliability, I would use a USB based solution and maybe a timer to periodically close a time stamped file and open a new file. You might do that once per hour, or once per 5, 10, 15 minutes, your choice.

I had 7 Arduino UNO devices, 2 Arduino Mega devices and a Raspberry Pi communicating on I2C with 4 I2C LCD 20x4 screens.  I setup the master to loop communication on the addresses for each slave.   I was able to send and receive information from the slaves to the master and display it on the I2C LCD screens.  

@scsiraidguru And?

Did you try to get I2C working first and making sure SPI was not conflicting with it.

Posted by: @scsiraidguru

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I had 7 Arduino UNO devices, 2 Arduino Mega devices and a Raspberry Pi communicating on I2C with 4 I2C LCD 20x4 screens.  I setup the master to loop communication on the addresses for each slave.   I was able to send and receive information from the slaves to the master and display it on the I2C LCD screens.  

-- attachment is not available --

What does all that stuff do?

@henrik_t7 I have attached a screen grab of the Arduino UNO R4 WiFi specs. I see no evidence they designed the board to not be able to use all bus protocols at the same time. If you are seeing failures, I would look at the wiring and code.

Thanks for all the replies, it seems that the sensor reads the temperature and shows it on my oled display and on the serial monitor. The program does not make the last if statement and takes the else statement. lines 72 to 80

@henrik_t7 No surprise. Did it ever open the file? I am 100% sure Arduino did not design their product in a way that you can't use SPI and I2C at the same time. If the file was never successfully opened and written to I would suspect a bad card, or bad wiring. If it did open and write at the beginning then that likely means the card is full.

I have found a sketch on the web where you can test whether my SD card works and you could write to the SD card. so it works

* Created by ArduinoGetStarted.com
 *
 * This example code is in the public domain
 *
 * Tutorial page:  https://arduinogetstarted.com/tutorials/arduino-write-variable-to-sd-card 
 */

#include <SD.h>

#define PIN_SPI_CS 4

File myFile;
int myInt = -52;
float myFloat = -12.7;
String myString = "HELLO";
char myCharArray[] = "ArduinoGetStarted.com";
byte myByteArray[] = {'1', '2', '3', '4', '5'};

void setup() {
  Serial.begin(9600);

  if (!SD.begin(PIN_SPI_CS)) {
    Serial.println(F("SD CARD FAILED, OR NOT PRESENT!"));
    while (1); // don't do anything more:
  }

  Serial.println(F("SD CARD INITIALIZED."));
  Serial.println(F("--------------------"));
  SD.remove("arduino.txt"); // delete the file if existed

  // create new file by opening file for writing
  myFile = SD.open("arduino.txt", FILE_WRITE);

  if (myFile) {
    myFile.println(myInt);    // write int variable to SD card in line
    myFile.println(myFloat);  // write float variable to SD card in line
    myFile.println(myString); // write String variable to SD card in line
    myFile.println(myCharArray); // write char array to SD card in line
    myFile.write(myByteArray, 5);
    myFile.write("\n"); // new line

    for (int i = 0; i < 5; i++) {
      myFile.write(myByteArray[i]); // new line

      if (i < 4)
        myFile.write(","); // comma
    }
    myFile.write("\n"); // new line

    myFile.close();
  } else {
    Serial.print(F("SD Card: error on opening file arduino.txt"));
  }

  // open file for reading
  myFile = SD.open("arduino.txt", FILE_READ);
  if (myFile) {
    while (myFile.available()) {
      char ch = myFile.read(); // read characters one by one from Micro SD Card
      Serial.print(ch); // print the character to Serial Monitor
    }
    myFile.close();
  } else {
    Serial.print(F("SD Card: error on opening file arduino.txt"));
  }
}

void loop() {
}

@henrik_t7 You need to post the entire sketch, there are things you have to do in advance of using the SD card. It's all there in the example.

I don't understand,

when I only use I2c with Oled display and temperature sensor, it works super fine together with arduino uno r4, reads the temperature on the Oled display fine.

When I then use the same SPI with SD card and temperature sensor, it cannot write temperature to the SD card?? It seems that the SD card does not open.

That's only if I have both wires for I2c and wires for SPI at the same time .

If I do a test of SPI card with SPI wires mounted and no wires for I2c, can it write data on the SD card??

Has anyone made a test whether the arduino uno r4 can use I2c and SPI at the same time???

You could setup the pin change interrupt and setup the buffer to store the SPI data then set the interrupt to change to the I2C bus.  They won't work at the same time.  The Giga has 3 IRQs that might be able to use SPI on one IRQ and I2C on another IRQ.  The Mega should have enough memory and flash to accomplish it.  I usually use my Mega devices for the I2C Master.  The Arduino UNO/Hero as slaves with the I2C devices like my LCD Screens for output.  Remember I2C is half duplex and SPI is full duplex.   I have used my Raspberry Pi 4B as the I2C Master because it has more resources.  

I2C Sensors
You might check for I2C Sensors instead of using SPI and I2C.