Unable to test SPI interface

Question

I followed the instructions given in the blog and everything got executed without any errors. But in the end

https://www.raspberrypi.org/documentation/hardware/raspberrypi/spi/README.md

Ran this script:

wget https://raw.githubusercontent.com/raspberrypi/linux/rpi-3.10.y/Documentation/spi/spidev_test.c
gcc -o spidev_test spidev_test.c
./spidev_test -D /dev/spidev0.0

Expected output:

spi mode: 0
bits per word: 8
max speed: 500000 Hz (500 KHz)

FF FF FF FF FF FF
40 00 00 00 00 95
FF FF FF FF FF FF
FF FF FF FF FF FF
FF FF FF FF FF FF
DE AD BE EF BA AD
F0 0D

Output which I got:

spi mode: 0
bits per word: 8
max speed: 500000 Hz (500 KHz)

00 00 00 00 00 00
00 00 00 00 00 00
00 00 00 00 00 00
00 00 00 00 00 00
00 00 00 00 00 00
00 00 00 00 00 00
00 00 

I did connect MOSI and MISO. Also lsmod does show spibcm2708 drivers being enabled.

I tested the same tutorial on 2 Raspberry Pi, but same result. Where am I going wrong? What am I missing?

EDIT:

Error fixed. Thanks to @dastaan for spotting. I was using a 26 pin reference and hence was doing a wrong connection. It's working fine for me now.

Answer 1

Error fixed. Thanks to @dastaan for spotting.

My bad. I was using a 26 pin reference and hence was doing a wrong connection. I used this reference given below and it started working for me.

Answer 2

It may be because the SPI struture is not fully initialised. This error did not use to matter but now causes problems.

struct spi_ioc_transfer tr = {
        .tx_buf = (unsigned long)tx,
        .rx_buf = (unsigned long)rx,
        .len = ARRAY_SIZE(tx),
        .delay_usecs = delay,
        .speed_hz = speed,
        .bits_per_word = bits,
    };

Perhaps try.

struct spi_ioc_transfer tr;
memset(&tr, 0, sizeof(tr));
tr.tx_buf = (unsigned long)tx;
tr.rx_buf = (unsigned long)rx;
tr.len = ARRAY_SIZE(tx);
tr.delay_usecs = delay;
tr.speed_hz = speed;
tr.bits_per_word = bits;

---

Edited to add.

The wrong gpios are being used. For the standard SPI device MOSI is pin 19 and MISO is pin 21.

           pin  pin
3V3         1    2      5V
0/2 (SDA)   3    4      5V
1/3 (SCL)   5    6      0V
4           7    8      14 (TXD)
0V          9   10      15 (RXD)
17 (ce1)   11   12      18 (ce0)
21/27      13   14      0V
22         15   16      23
3V3        17   18      24
10 (MOSI)  19   20      0V
9 (MISO)   21   22      25
11 (SCLK)  23   24      8 (CE0)
0V         25   26      7 (CE1)
           .......
0 (ID_SD)  27   28      1 (ID_SC)
5          29   30      0V
6          31   32      12
13         33   34      0V
19 (miso)  35   36      16 (ce2)
26         37   38      20 (mosi)
0V         39   40      21 (sclk)