test_i2c.lua

--
-- lua-periphery by vsergeev
-- https://github.com/vsergeev/lua-periphery
-- License: MIT
--

require('test')
local periphery = require('periphery')
local I2C = periphery.I2C

--------------------------------------------------------------------------------

local device = nil
local eeprom_address = nil

--------------------------------------------------------------------------------

function test_arguments()
    local i2c = nil

    ptest()

    -- Open with invalid type
    passert_periphery_error("open invalid type", function () i2c = I2C(123) end, "I2C_ERROR_ARG")
end

function test_open_config_close()
    local i2c = nil

    ptest()

    -- Make sure module version exists
    passert("module version", I2C.version ~= nil)

    -- Open non-existent i2c device
    passert_periphery_error("non-existent device", function () i2c = I2C("/foo/bar") end, "I2C_ERROR_OPEN")

    -- Open legitimate i2c device
    passert_periphery_success("open i2c", function () i2c = I2C(device) end)
    passert("fd > 0", i2c.fd > 0)
    io.write(string.format("i2c: %s\n", i2c:__tostring()))

    -- Close i2c
    passert_periphery_success("close i2c", function () i2c:close() end)
end

function test_loopback()
    local i2c = nil

    ptest()

    -- "Loopback" plan:
    --  1. Read EEPROM via sysfs
    --  2. Read it ourselves via i2c_*() and compare data

    -- Read EEPROM via sysfs
    local sysfs_path = string.format("/sys/bus/i2c/devices/%s-00%02x/eeprom", string.sub(device, #device), eeprom_address)
    local f = io.open(sysfs_path, "rb")
    passert("open sysfs eeprom file", f ~= nil)
    local eeprom_data_str = f:read(256)
    f:close()

    -- Convert EEPROM data string to a bytes table
    local eeprom_data = {}
    for i = 1,#eeprom_data_str do
        eeprom_data[i] = eeprom_data_str:sub(i,i):byte()
    end

    -- Read it ourselves and compare
    passert_periphery_success("open i2c", function () i2c = I2C(device) end)

    local buf = ""
    for addr = 0, 255 do
        local msgs = { { 0x00, addr }, { 0x00, flags = I2C.I2C_M_RD } }
        passert_periphery_success("transfer", function () i2c:transfer(eeprom_address, msgs) end)
        if msgs[2][1] ~= eeprom_data[addr+1] then
            pfail(string.format("data mismatch at address %d (expected %02x, got %02x)", addr, string.byte(eeprom_data[addr+1]), msgs[2][1]))
            os.exit(1)
        end
    end

    passert_periphery_success("close i2c", function () i2c:close() end)
end

function test_interactive()
    local i2c = nil

    ptest()

    passert_periphery_success("open i2c", function () i2c = I2C(device) end)

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

    -- 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
    local msgs = { { 0xaa, 0xbb, 0xcc, 0xdd } }

    print("Press enter to start transfer...")
    io.read()
    passert_periphery_error("transfer to non-existent device", function () i2c:transfer(0x7a, msgs) end, "I2C_ERROR_TRANSFER", 121)
    passert_periphery_success("close i2c", function () i2c:close() end)

    print("I2C transfer occurred? y/n")
    passert("interactive success", io.read() == "y")
end

if #arg < 3 then
    io.stderr:write(string.format("Usage: lua %s <I2C device #1> <EEPROM address> <I2C device #2>\n\n", arg[0]))
    io.stderr:write("[1/4] Arguments test: No requirements.\n")
    io.stderr:write("[2/4] Open/close test: I2C device #1 should be real.\n")
    io.stderr:write("[3/4] Loopback test: I2C device #1 should have an EEPROM attached.\n")
    io.stderr:write("[4/4] Interactive test: I2C device #2 should be observed with a logic analyzer.\n\n")
    io.stderr:write("Hint: for BeagleBone Black, use onboard EEPROM on /dev/i2c-0, and export I2C1 to /dev/i2c-2 with:\n")
    io.stderr:write("    echo BB-I2C1A1 > /sys/devices/bone_capemgr.9/slots\n")
    io.stderr:write("to enable I2C1 (SCL=P9.24, SDA=P9.26), then run this test:\n")
    io.stderr:write(string.format("    lua %s /dev/i2c-0 0x50 /dev/i2c-2\n\n", arg[0]))
    os.exit(1)
end

device = arg[1]
eeprom_address = tonumber(arg[2])

test_arguments()
pokay("Arguments test passed.")
test_open_config_close()
pokay("Open/close test passed.")
test_loopback()
pokay("Loopback test passed.")
device = arg[3]
test_interactive()
pokay("Interactive test passed.")

pokay("All tests passed!")