`analogRead()`¶

Reads the current value from an analog input channel and returns it as an integer from 0 to 1023.

Signature¶

int analogRead(int pin);

Parameters¶

Parameter	Type	Description
`pin`	`int`	The ADC channel to read from (e.g., `X_INPUT` for the joystick X axis)

Return value¶

An int between 0 and 1023, representing the measured voltage as a 10-bit value.

0 corresponds to 0 V (minimum voltage).
1023 corresponds to the reference voltage (maximum voltage).

How it works¶

The Raspberry Pi's GPIO pins cannot directly read analog voltages. An external chip called the MCP3008 (an Analog-to-Digital Converter, or ADC) reads the voltage and converts it to a digital number. The mcp3004Setup() call in setup() configures the MCP3008 and maps its channels to pin numbers starting at a base address. You do not need to call mcp3004Setup() yourself — it is already in the provided setup code.

After setup, you call analogRead() with the channel's pin number (e.g., X_INPUT, which equals 100) to get the current reading.

Example¶

Reading a light sensor on ADC channel 101 and printing the value:

unsigned lightLevel = analogRead(101);
printf("Light level: %4d\n", lightLevel);

Note: channel 101 is just an illustration. In the labs, use the named constants defined in your .c file — do not use bare numbers.

analogRead()¶