## by Fabien Chouteau – Oct 20, 2020

Welcome to the Ada for micro:bit series where we look at simple examples to learn how to program the BBC micro:bit with Ada.

In this sixth part we will see how to read the analog value of a pin. This means reading a value between 0 and 1023 that tells the voltage applied to the pin. 0 means 0 volts, 1023 means 3.3 volts.

### Wiring Diagram

For this example we will need a couple of extra parts:

• An LED
• A 470 ohm resistor
• A potentiometer
• A couple of wires to connect them all

For this example we start from the same circuit as the pin output example, and we add a potentiometer. The center pin of the potentiometer is connected to pin 1 of the micro:bit the other two pins are respectively connected to GND and 3V.

### Interface

To read the analog value of the IO pin we are going to use the function Analogof the package MicroBit.IOs.

function Analog (Pin : Pin_Id) return Analog_Value
with Pre => Supports (Pin, Analog);
--  Read the voltagle applied to the pin. 0 means 0V 1023 means 3.3V

Arguments:

• Pin : The id of the pin that we want read the analog value from

Precondition:

• The function Analog has a precondition that the pin must support analog IO.

In the code, we are going to write an infinite loop that reads the value of pin 1, and set pin 0 to the same value.

This means that you can control the brightness of the LED using the potentiometer.

Here is the full code of the example:

with MicroBit.IOs;

procedure Main is

Value : MicroBit.IOs.Analog_Value;
begin

--  Loop forever
loop

--  Read analog value of pin
Value := MicroBit.IOs.Analog (1);

--  Write analog value of pin 0
MicroBit.IOs.Write (0, Value);
end loop;
end Main;

Following the instructions of Part 1 you can open this example (Ada_Drivers_Library-master\examples\MicroBit\analog_in\analog_in.gpr), compile and program it on your micro:bit.

See you next week for another Ada project on the micro:bit.

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