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This section explains how to use the Analog-to-Digital Converter (ADC) on the obniz IO pins to measure analog voltage.

Overview

By using the ad.get(IO) function, you can read the voltage applied to a specific IO pin as a numerical value. This is useful for retrieving data from analog sensors such as temperature, light, or pressure sensors.

Function Description

ad.get(pin_number)

• Description: Measures the voltage on the specified IO pin.
• Parameters:
• pin_number (number): The ID of the IO pin you wish to measure.

• Return Value:
• Returns the measured voltage in Volts (V).

Code Example

The following Lua script demonstrates how to continuously read the analog voltage from IO Pin 1 and log it to the console.

-- This function runs repeatedly when the device is offline
function on_offline_loop()
  loop()
end

-- This function runs repeatedly when the device is online
function on_online_loop()
  loop()
end

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

-- Set Pin 1 to retain its state (keep it active for ADC)
io.retain(1, true);

-- Main Loop
function loop()
  -- Wait for 100ms to prevent excessive processing
  os.wait(100);
  
  -- Retrieve voltage from Pin 1 and log the value
  -- The value is returned in Volts (e.g., 1.25v)
  os.log("AD1: " .. ad.get(1) .. "v");
end

Key Points

• io.retain: In this script, io.retain(1, true) is used to ensure the pin remains in a state where it can be measured consistently.
• Polling Interval: The os.wait(100) is included to manage the sampling rate. You can adjust this value depending on how frequently you need to monitor the sensor data.
• Unit: Note that the value returned by ad.get() is already scaled to Volts, so no complex conversion from raw 10-bit or 12-bit integers is required.