SPI stops functioning once Serial or Delay are used

[forseenendingh]

Using a Mega2560 Writing my first SPI library to become more familiar with the protocol. Was having a hard time as it appeared that the Arduino was refusing to send any data, oscilloscope seemed to confirm this was the voltages would not fluctuate. As a sanity check I tried the Arduino example, which worked and I was able to see the data on the oscilloscope. I compared my code to the example and from trial and error I found that the SPI library was not working when delay or Serial.print was added to the code (was using them for debugging). Changing the delay from 1000 to 1 and slowing down the bus seems to resolve this, increasing delay or bus speed causes it to fail again. What can I do to work around this?

#include <SPI.h>

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

  SPI.begin();

  delay(100);
}

int i = 0;

void loop() {
  SPI.beginTransaction(SPISettings(10000000, MSBFIRST, SPI_MODE0)); // Using MCP2515 at 10 Mhz
  SPI.transfer(i++ % 255); // Changing data to help show code is working on scope
  SPI.endTransaction();
  delay(1); // Delay of 1 breaks SPI
}

[van_der_decken]

I'm a bit confused. You wrote that "Changing the delay from 1000 to 1 and slowing down the bus seems to resolve this", which I take to mean that a delay of 1 mSec makes it appear to work for you. But in your code you say that "Delay of 1 breaks SPI". Which is it?

[forseenendingh]

I have since figured out it was an issue with the scope not being turned to a low enough sec/div so it wasn't trigging like I was expecting. The no delay was just making the bus more active and therefor easier to see. Appears to be working now.