io.output(io, boolean)

Changes the state of a specified IO pin between High and Low.
When this function is called, the IO pin—which is in a high-impedance (Hi-z) state upon startup—begins push-pull output.

Arguments

Example: Alternating LED Blink

The following example demonstrates how to blink two LEDs connected to IO1 and IO2 alternately.

local tick = 0
local flag = false

-- Log message to indicate startup
os.log(" - Lua PowerOn");

-- Retain the state of IO1 and IO2 even during sleep or disconnection
io.retain(1, true);
io.retain(2, true);

-- Loop executed when the device is offline
function on_offline_loop()
  loop()
end

-- Loop executed when the device is online
function on_online_loop()
  loop()
end

-- Main logic to toggle IO states every 300ms
function loop()
  -- Check if 300ms has passed since the last toggle
  if tick + 300 < os.getTick() then
    tick = os.getTick()
    
    -- Output High/Low to pins 1 and 2 alternately
    io.output(1, flag);
    io.output(2, not flag);
    
    -- Toggle the flag state
    flag = not flag
  end
end

io.input(io)

Reads the High/Low state of a specified IO pin.

By calling the input function after an output operation, you can set the IO pin to a Hi-z (High Impedance) state.

Functionality

• Read Logic Levels: Detects whether the voltage on a pin is High or Low.
• State Control: Transitions the pin to a High Impedance state when used following an output command.

Code Example

The following example demonstrates how to read the input from IO2 and output that state directly to IO1.

-- Loop execution while the device is offline
function on_offline_loop()
  loop()
end

-- Loop execution while the device is online
function on_online_loop()
  loop()
end

-- Core logic to sync IO1 with IO2
function loop()
  -- Read the state of IO2 and output it to IO1
  io.output(1, io.input(2));
end

-- Initialization
os.log(" - Lua Start");

-- Maintain the state of the IO pins
io.retain(1, true);
io.retain(2, true);

Parameters

• io.input(pin_number): Returns the current state (true/false or 1/0) of the specified pin.
• io.output(pin_number, value): Sets the specified pin to the given value.

Notes

Using io.input is an effective way to reset a pin from an active output state back to a neutral, high-impedance monitoring state.

io.drive(io, mode)

Selects the output drive method of a pin.

Available for OS7.1.0 and later

Arguments

Note: "5v" is available only on obniz Board. On the ESP32 family, IO operates at 3V.

io.drive(1, "open-drain");  -- Drive IO1 as open-drain
io.output(1, true);

io.pull(io, mode)

Selects the pull resistor applied to a pin.

Available for OS7.1.0 and later

Arguments

Note: "5v" is available only on obniz Board. On the ESP32 family, IO operates at 3V.

io.pull(2, "3v");       -- Pull IO2 up to 3V
local val = io.input(2);

io.pull(2, nil);        -- Back to floating (no pull resistor)