Using hardware SPI on Feather M4 doesn't appear to work

[makermelissa]

When trying to run this using Hardware SPI (SCK and MOSI), it doesn't appear to be working at all as in none of the lights do anything. I was able to run just fine on the Raspberry Pi using Hardware SPI.

[ladyada]

what happens if you slow it down to 1mhz
does software SPI work
did you try powering the LEDs from 3.3V

[makermelissa]

It’s at 1MHz. I tried 1KHz too. Software SPI works fine.

[makermelissa]

I didn’t try powering at 3.3v.

[ladyada]

did you verify signal comes out on the hardware SPI pins with an oscilloscope?

[makermelissa]

No, I haven’t done that yet. I was stopping for the night and was just putting the issue here. Thanks for the suggestions on some things to try.

[ladyada]

oki!

[makermelissa]

Here's with Hardware SPI:

Here's with Software:

One thing I noticed right away between the two is that between sets of pulses the line is high with hardware and low with software.

[ladyada]

try different hardware MODEs

[makermelissa]

Yeah, that's what I was thinking.

[makermelissa]

Just to be complete, here's the output on the Hardware SPI on Raspberry Pi (which is working). This matches the working CP Software SPI output with MOSI being low between pulses.

Playing with Phase and Polarity only seemed to affect the clock and not MOSI. I'll keep digging.

[makermelissa]

Ok, I can't seem to find a way to make MOSI go low when idle and it seems to be losing bytes here and there. Changing Phase to 1 has limited success in flashing the first light, but the colors is wrong. So I'm just going to finish up the guide and note this.

[dhalbert]

The resting level of SERCOM MOSI in SPI mode on AVR, SAMD21 and SAMD51 is high. I see this both in CircuitPython (I tried the latest version (ASF4) and also 2.3.1 (ASF3). I also tried the simple program below in Arduino on a Feather M0 and also on an ItsyBitsy 32u4, and MOSI also remains high when quiescent.

So my guess is that this code never worked with hardware SPI on any typical microcontroller platform.

#include <SPI.h>

void setup() {#include <SPI.h>

void setup() {
  SPI.begin();
}

void loop() {
  SPI.transfer(0xff);
  delay(100);
  SPI.transfer(0x00);
  delay(100);
}
  SPI.begin();
}

void loop() {
  SPI.transfer(0xff);
  delay(100);
  SPI.transfer(0x00);
  delay(100);
}

[makermelissa]

That's pretty much the conclusion I was coming to. Thanks for chiming in.