Digital output

In simple electrical terms for our Raspberry Pi, when we drive a GPIO pin high, its voltage measures ~3.3 volts, and when we drive it low, it measures ~0 volts.

Let's observe this using a multimeter:

Different multimeters may have different connections and labeling than the multimeter illustrated here. Consult your multimeter's manual if you are unsure how to set it up for measuring voltage.

1. Set your multimeter to its voltage setting and attach it to GPIO 21 and GND, as shown in the following diagram:

Figure 6.3 – Connecting a multimeter to a GPIO pin

2. Run the following code, which you can find in the chapter06/digital_output_test.py file. You will notice that the meter toggles between about 0 volts and about 3.3 volts. I say about because nothing is ever really perfect or precise in electronics; there are always tolerances. Here's a synopsis of the code:

# ... truncated ...
GPIO_PIN = 21
pi = pigpio.pi()
pi.set_mode(GPIO_PIN, pigpio...