local GPIO = require('periphery').GPIO

-- Open GPIO /dev/gpiochip0 line 10 with input direction
local gpio_in = GPIO("/dev/gpiochip0", 10, "in")
-- Open GPIO /dev/gpiochip0 line 12 with output direction
local gpio_out = GPIO("/dev/gpiochip0", 12, "out")

local value = gpio_in:read()
gpio_out:write(not value)

gpio_in:close()
gpio_out:close()

local LED = require('periphery').LED

-- Open LED led0
local led = LED("led0")

-- Turn on LED (set max brightness)
led:write(true)

-- Set half brightness
led:write(math.floor(led.max_brightness / 2))

-- Turn off LED (set zero brightness)
led:write(false)

led:close()

local PWM = require('periphery').PWM

-- Open PWM chip 0, channel 10
local pwm = PWM(0, 10)

-- Set frequency to 1 kHz
pwm.frequency = 1e3
-- Set duty cycle to 75%
pwm.duty_cycle = 0.75

-- Enable PWM output
pwm:enable()

pwm:close()

local SPI = require('periphery').SPI

-- Open spidev1.0 with mode 0 and max speed 1MHz
local spi = SPI("/dev/spidev1.0", 0, 1e6)

local data_out = {0xaa, 0xbb, 0xcc, 0xdd}
local data_in = spi:transfer(data_out)

print(string.format("shifted out {0x%02x, 0x%02x, 0x%02x, 0x%02x}", unpack(data_out)))
print(string.format("shifted in  {0x%02x, 0x%02x, 0x%02x, 0x%02x}", unpack(data_in)))

spi:close()

local I2C = require('periphery').I2C

-- Open i2c-0 controller
local i2c = I2C("/dev/i2c-0")

-- Read byte at address 0x100 of EEPROM at 0x50
local msgs = { {0x01, 0x00}, {0x00, flags = I2C.I2C_M_RD} }
i2c:transfer(0x50, msgs)
print(string.format("0x100: 0x%02x", msgs[2][1]))

i2c:close()

local MMIO = require('periphery').MMIO

-- Open am335x real-time clock subsystem page
local rtc_mmio = MMIO(0x44E3E000, 0x1000)

-- Read current time
local rtc_secs = rtc_mmio:read32(0x00)
local rtc_mins = rtc_mmio:read32(0x04)
local rtc_hrs = rtc_mmio:read32(0x08)

print(string.format("hours: %02x minutes: %02x seconds: %02x", rtc_hrs, rtc_mins, rtc_secs))

rtc_mmio:close()

-- Open am335x control module page
local ctrl_mmio = MMIO(0x44E10000, 0x1000)

-- Read MAC address
local mac_id0_lo = ctrl_mmio:read32(0x630)
local mac_id0_hi = ctrl_mmio:read32(0x634)

print(string.format("MAC address: %04x%08x", mac_id0_lo, mac_id0_hi))

ctrl_mmio:close()

local Serial = require('periphery').Serial

-- Open /dev/ttyUSB0 with baudrate 115200, and defaults of 8N1, no flow control
local serial = Serial("/dev/ttyUSB0", 115200)

serial:write("Hello World!")

-- Read up to 128 bytes with 500ms timeout
local buf = serial:read(128, 500)
print(string.format("read %d bytes: _%s_", #buf, buf))

serial:close()

-- Example of error caught with pcall()
> status, err = pcall(function () spi = periphery.SPI("/dev/spidev1.0", 0, 1e6) end)
> =status
false
> dump(err)
{
  message = "Opening SPI device \"/dev/spidev1.0\": Permission denied [errno 13]",
  c_errno = 13,
  code = "SPI_ERROR_OPEN"
}
> 

-- Example of error propagated to user
> periphery = require('periphery')
> spi = periphery.SPI('/dev/spidev1.0', 0, 1e6)
Opening SPI device "/dev/spidev1.0": Permission denied [errno 13]
> 

> periphery = require('periphery')
> gpio = periphery.GPIO(14, 'in')
(error object is not a string)
> 

> periphery = require('periphery')
> gpio, err = pcall(periphery.GPIO, 14, 'in')
> =tostring(err)
Opening GPIO: opening 'export': Permission denied [errno 13]
> print(err)
Opening GPIO: opening 'export': Permission denied [errno 13]
> =err
Opening GPIO: opening 'export': Permission denied [errno 13]
>