SPI stopped working on Model B 2

Question

Possibly related question: spi stopped working after upgrade

Background

I have had SPI working on my RPi 2 model B. I stopped using it for a couple of months, and now that I'm trying to use it again (with the exact same code) it is no longer working.

I can't think what might have caused it. I'm pretty sure I did an update during that time, but I can't see the commands anywhere in the command-line history, so I could have dreamed that. The contents of /proc/version is:

Linux version 4.1.15-v7+ (dc4@dc4-XPS13-9333) (gcc version 4.8.3 20140303 (prerelease) (crosstool-NG linaro-1.13.1+bzr2650 - Linaro GCC 2014.03) ) #830 SMP Tue Dec 15 17:02:45 GMT 2015

Symptoms

A logic analyser is attached to the SPI pins. When I run either of these two commands:

echo -ne "\x01\x02\x03" > /dev/spidev0.0
echo -ne "\x01\x02\x03" > /dev/spidev0.1

nothing is seen on the analyser.

/dev/spidev0.0 and /dev/spidev0.1 both exist. dtparam=spi=on is set. When I run my previously working code, I get no error messages, and the code seems to be able to set things like the clock speed, and read it back correctly.

Everything seems in order, except for the lack of a signal.

Question

What should I look for to debug this?

Update

I have upgraded. Linux version is now:

Linux version 4.4.38-v7+ (dc4@dc4-XPS13-9333) (gcc version 4.9.3 (crosstool-NG crosstool-ng-1.22.0-88-g8460611) ) #938 SMP Thu Dec 15 15:22:21 GMT 2016

/boot/config.txt still contains dtparam=spi=on

And still nothing is seen on the logic analyser when I try to echo to /dev/spidev0.0 or /dev/spidev0.1.

Answer 1

Turns out that somehow the connector plugged into the GPIO header had become unplugged and plugged back in 1 pin off, so it wasn't getting 3.3v and GND. I suppose it must have been me that did it, though I can't remember taking it all apart to do that.