Pro-HAT & GPIO-Zero for the Raspberry Pi

HATs or Hardware Attached on Top are very popular with the Raspberry Pi (RBPi) community. They plug on to the GPIO pins on the RBPi, providing additional functionality to the single board computer. The Pro-HAT puts the GPIO ports of an RBPi in numerical order, and labels them clearly. The user gets a female socket for each port into which, they can plug their wires or component leads.

Pro-HAT is actually a 72-point breadboard with the arranged GPIO ports and includes plenty of power and GND sockets, which every experimenter looks for when playing with some electronics. For instance, when plugging in LEDs, one does not need any current-limiting resistors, since these are already built-in.

Pro-HAT provides a protection circuit on each GPIO port. This protects the GPIO ports from any incorrect wiring, which happens during experimentation. However, you must still be careful not to short the 3V3 or 5 V pins directly to GND, as this can do serious damage.

However, it is still possible to bypass the 330 Ohm resistors on the Pro-HAT board. The board has an unprotected side where the ports are available as through-holes, without protection. This is especially useful for buzzers, which usually require more than the 10 mA current limit to operate than the resistors impose.

Created by Dave Jones and Ben Nuttal, the GPIO-Zero is the ideal way to start with Python GPIO programming. The user finds it very simple, as there is nothing to install when using it to start with the Pro-HAT. The GPIO-Zero kit has plenty of components, making it realistic for individuals and schools in discovering the joys of controlling the world with the RBPi, the Pro-HAT, and the GPIO-Zero kit.

The GPIO-Zero kit contains an MCP3008 ADC Chip, a TMP-36 analog temperature sensor, a single-channel relay, a PIR motion sensor, five 10 mm LEDs, a 10 K potentiometer, a 40-way male header, a large button, a 10 k resistor, 20 male-to-male jumper leads, and 20 male-to-female jumper leads.

The Pro-HAT protects ports by using a 330 Ohm resistor in series with each port, which does not allow currents over 10 mA into or out of the port. There is also a 3V3 Zener diode on the port, which saves the port from any overvoltage. Further, GPIO pins 2, 3, and 26 have hardware pull-ups, which means each of these pins are pulled up to 3V3 by resistors or 2 k value. This makes the default state of these pins to remain high, until an external signal pulls them low. Likewise, GPIO pins 2 & 3, which are also the I2C ports, are pulled down to zero volts through resistors of 2 k value. This keeps these pins grounded, but an external signal can pull them high.

Pulling the pins high and low through resistors on the Pro-HAT works well for experiments the GPIO-Zero kit allows. However, the resistors and the protection circuitry may not work well with high-speed SPI devices, such as the PiTFT and other small SPI LED color screens. In such cases, simply unplugging the Pro-HAT will solve the problem.