SPI is only working with pi@raspberrypi:$ pigs spio 0 50000 0

Question

I enabled SPI on my Raspberry pi 4 like in many Tutorials explained.

In sudo raspi-config I enabled SPI. In /boot/config.txt I added dtparam=spi=on

$ ls -l /dev/spidev*** shows

crw-rw---- 1 root spi 153, 0 Jul 23 12:43 /dev/spidev0.0

crw-rw---- 1 root spi 153, 1 Jul 23 12:43 /dev/spidev0.1

$ lsmod | grep -i spi** shows

spidev                 20480  0

spi_bcm2835            24576  0

But if I try a SPI Loopbacktest https://github.com/rm-hull/spidev-test

it shows

$ ./spidev_test -v

spi mode: 0x4
bits per word: 8
max speed: 500000 Hz (500 KHz)
TX | 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 F0 0D  | ......@....?..................?.
RX | 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  | ................................

until I write:

$ sudo pigpiod

$ pigs spio 0 50000 0**

in the Console

Then the Loopbacktest works and it shows:

spi mode: 0x4
bits per word: 8
max speed: 500000 Hz (500 KHz)
TX | 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 F0 0D  | ......@....�..................�.
RX | 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 F0 0D  | ......@....�..................�.

EDIT:

With another Script based on spidev I have the same problems.

from   time import sleep
import spidev

spiPort0 = spidev.SpiDev()
spiPort0.open(0,0)
spiPort0.max_speed_hz = 100000

def spiSendRecvOneByte(spiPort, sendByte):
    sendByteArray = [sendByte]
    recvByteArray = spiPort.xfer(sendByteArray)    
    return recvByteArray

def repeatSendOneByte(spiPort, sendByte, pauseTimeBetweenBytes, repeatCount):
    print('\nBegin repeatSendByte(),....')
    for i in range(repeatCount):
        spiSendRecvOneByte(spiPort, sendByte)
        sleep(pauseTimeBetweenBytes)
    print('End   repeatSendByte().')
    return

def loopBackOneByte(spiPort, sendByte):
    recvByteArray     = spiSendRecvOneByte(spiPort, sendByte)
    recvByte          = recvByteArray[0]

    print('\nBegin testLoopbackOneByte(),....')
    #print('')
    print('      sendByte  = ', hex(sendByte))
    print('      recvByte  = ', hex(recvByte))
    #print('')
    print('End   testLoopbackOneByte(),....')
    return

def testRepeatSendOneByte():
    repeatSendOneByte(spiPort0, 0x5b, 0.0001, 2000000)
    return

def testLoopbackOneByte():
    loopBackOneByte(spiPort0, 0x5b)
    return

#testRepeatSendOneByte()
testLoopbackOneByte()

''' Smple output tlfong 01 2019apr07hkt2047
Begin testLoopbackOneByte(),....
      sendByte  =  0x5b
      recvByte  =  0x5b
End   testLoopbackOneByte(),....
'''

# *** End ***

When I reboot the system SPI is not working and I have to write the commands angain. I can't explain this situation and I was searching a lot for this Error.

I would be very happy if someone could help me and explain to me why SPI works after these commands and what I could do to keep it like this after the restart.

EDIT: I got a solution in newinstalling the Raspberry pi OS. Now SPI loopbacktest is working fine and also a small Project with the MCP3002 analog to digital converter

Best Regards

Sven

Answer 1

I think it is a fault in spidev_test.c. I note it hasn't been updated for several years.

There was a change in the Linux SPI driver which meant it was important to zero the spi_ioc_transfer structure to make sure it was properly initialised.

Make the following change to your copy of spidev_test.c

From line 116.

struct spi_ioc_transfer tr;

memset(&tr, 0, sizeof(tr));

tr.tx_buf = (unsigned long)tx;
tr.rx_buf = (unsigned long)rx;
tr.len = len;
tr.delay_usecs = delay;
tr.speed_hz = speed;
tr.bits_per_word = bits;

pigpio/pigs is not relevant as it does not use the Linux SPI driver.