test_i2c.py

import os
import random
import sys
import time

import periphery
from .test import ptest, pokay, passert, AssertRaises

if sys.version_info[0] == 3:
    raw_input = input


i2c_devpath = None
i2c_eeprom_addr = 0x51


def test_arguments():
    ptest()

    # Open with invalid type
    with AssertRaises("open invalid type", TypeError):
        periphery.I2C(123)


def test_open_close():
    ptest()

    # Open non-existent device
    with AssertRaises("non-existent device", periphery.I2CError):
        periphery.I2C("/foo/bar")

    # Open legitimate device
    i2c = periphery.I2C(i2c_devpath)
    passert("fd >= 0", i2c.fd >= 0)

    # Close I2C
    i2c.close()


def test_loopback():
    ptest()

    # Generate random byte vector
    vector = [random.randint(0, 255) for _ in range(32)]

    i2c = periphery.I2C(i2c_devpath)

    # Write vector to 0x100 with list
    # S [ addr W ] [ 0x01 ] [ 0x00 ] [ Data... ] P
    msgs = [periphery.I2C.Message([0x01, 0x00] + vector)]
    i2c.transfer(i2c_eeprom_addr, msgs)

    # Wait for write cycle
    time.sleep(0.01)

    # Read from 0x100 with list
    # S [ addr W ] [ 0x01 ] [ 0x00 ] S [ addr R ] [ Data... ] P
    msgs = [periphery.I2C.Message([0x01, 0x00]), periphery.I2C.Message([0x00] * 32, read=True)]
    i2c.transfer(i2c_eeprom_addr, msgs)

    # Verify bytes
    passert("verify bytes", msgs[1].data == vector)

    # Write vector to 0x200 with bytes
    # S [ addr W ] [ 0x02 ] [ 0x00 ] [ Data... ] P
    msgs = [periphery.I2C.Message(b"\x02\x00" + bytes(vector))]
    i2c.transfer(i2c_eeprom_addr, msgs)

    # Wait for write cycle
    time.sleep(0.01)

    # Read from 0x200 with bytes
    # S [ addr W ] [ 0x02 ] [ 0x00 ] S [ addr R ] [ Data... ] P
    msgs = [periphery.I2C.Message(b"\x02\x00"), periphery.I2C.Message(b"\x00" * 32, read=True)]
    i2c.transfer(i2c_eeprom_addr, msgs)

    # Verify bytes
    passert("verify bytes", msgs[1].data == bytes(vector))

    # Read from 0x110 with bytearray, in-place
    buf = bytearray(16)
    msgs = [periphery.I2C.Message(bytearray([0x01, 0x10])), periphery.I2C.Message(buf, read=True)]
    i2c.transfer(i2c_eeprom_addr, msgs, inplace=True)

    # Verify bytes
    passert("verify in-place readback", msgs[1].data == bytearray(vector[0x10:]))
    passert("verify in-place readback id", msgs[1].data is buf)

    i2c.close()

    print("Loopback test passed.")


def test_interactive():
    ptest()

    # Open device 2
    i2c = periphery.I2C(i2c_devpath)

    print("")
    print("Starting interactive test. Get out your logic analyzer, buddy!")
    raw_input("Press enter to continue...")

    # Check tostring
    print("I2C description: {}".format(str(i2c)))
    passert("interactive success", raw_input("I2C description looks ok? y/n ") == "y")

    # There isn't much we can do without assuming a device on the other end,
    # because I2C needs an acknowledgement bit on each transferred byte.
    #
    # But we can send a transaction and expect it to time out.

    # S [ 0x7a W ] [0xaa] [0xbb] [0xcc] [0xdd] NA
    messages = [periphery.I2C.Message([0xaa, 0xbb, 0xcc, 0xdd])]

    raw_input("Press enter to start transfer...")

    # Transfer to non-existent device
    with AssertRaises("transfer to non-existent device", periphery.I2CError):
        i2c.transfer(0x7a, messages)

    i2c.close()

    success = raw_input("I2C transfer occurred? y/n ")
    passert("interactive success", success == "y")


if __name__ == "__main__":
    if os.environ.get("CI") == "true":
        test_arguments()
        sys.exit(0)

    if len(sys.argv) < 2:
        print("Usage: python -m tests.test_i2c <I2C device>")
        print("")
        print("[1/4] Arguments test: No requirements.")
        print("[2/4] Open/close test: I2C device should be real.")
        print("[3/4] Loopback test: Expects 24XX32 EEPROM (or similar) at address 0x51.")
        print("[4/4] Interactive test: I2C bus should be observed with an oscilloscope or logic analyzer.")
        print("")
        print("Hint: for Raspberry Pi 3, enable I2C1 with:")
        print("   $ echo \"dtparam=i2c_arm=on\" | sudo tee -a /boot/config.txt")
        print("   $ sudo reboot")
        print("Use pins I2C1 SDA (header pin 2) and I2C1 SCL (header pin 3),")
        print("and run this test with:")
        print("    python -m tests.test_i2c /dev/i2c-1")
        print("")
        sys.exit(1)

    i2c_devpath = sys.argv[1]

    test_arguments()
    pokay("Arguments test passed.")
    test_open_close()
    pokay("Open/close test passed.")
    test_loopback()
    pokay("Loopback test passed.")
    test_interactive()
    pokay("Interactive test passed.")

    pokay("All tests passed!")