#!/usr/bin/env python

# Loopback test script
# Connect MOSI and MISO together
#
# For spidev0.0 or spidev0.1 on the Raspberry Pi those are 
#   pins GPIO10 and GPIO9 respectively
#   physical pins 19 and 21 respectively
#
# This example code is in the public domain.
#
# Michel Deslierres <https://sigmdel.ca/michel>
#
# May 4, 2020

import spidev
import time

SPI_BUS = 0          # spidev0
SPI_SS  = 0          # spidev0.0, can be 1 also
SPI_CLOCK = 1000000  # 1 Mhz

# setup SPI
spi = spidev.SpiDev(SPI_BUS, SPI_SS)
spi.max_speed_hz = SPI_CLOCK
 
# transfer 2 bytes at a time, ^C to exit
try:
    v = 0
    while True:
        send = [v, v+1]
        print("")
        print("TX:", send)
        print("RX:", spi.xfer(send))
        time.sleep(0.5)
        if v >= 254:
            v = 0
        else:
            v = (v+2)
finally:
    spi.close()