Garbled MISO data from SPI bus on a DUE

Projects Networking, Protocols, and Devices
1

I'm trying to use the SPI bus on my Due. I got the Due from Digikey so I assume it's official.
On a scope I'm looking at pins SCK & MISO from the SPI header and pin4 which I'm using for slave select.

Here's the code. Not much to it.

#include <SPI.h>

const int SSpin = 4;

void setup()
{
  pinMode(SSpin, OUTPUT);
  digitalWrite(SSpin, HIGH);
  SPI.begin();
  SPI.setClockDivider(255);
  digitalWrite(SSpin, LOW);
  SPI.transfer(0xaa);
  digitalWrite(SSpin, HIGH);
  SPI.end();
}

void loop()
{
  delay(1000);
}

and attached is a snapshot of the scope. The clock is clean and clear. 8 pulses. The slave select looks good. But the output pin MISO shows nothing. It should show a square wave (0xaa). Worse, if I change the data to 0xff I get a single pulse near the end that straddles the end of the slave select pulse. What could cause this weird behavior?

spitest.jpg

2

On a scope I'm looking at pins SCK & MISO from the SPI header and pin4 which I'm using for slave select.

You should have the o-scope probe connected to the MOSI line, not MISO.
Master Out - Slave In

3

Thank you Tim. That did the trick. I feel like an idiot. I'm glad you people dont know my real name. :sunglasses: