Part 1. GrovePi Zero Hardware
The first thing you will notice about the GrovePi Zero the second you unbox it is how small it is. Optimized to attach to a Raspberry Pi Zero, the GrovePi Zero is slightly longer in length than the Pi Zero and roughly the same width. Being compact is a huge advantage when deploying a real project in your home or business. The GrovePi Zero wins big points on this front.
The modular Grove system (more info) provides a standardized connector for every device, eliminating the need for a breadboard, add-on pull-up/down resistors, and tedious wiring. You simply plug-and-program. The primary purpose of the GrovePi Zero is to make hardware setup effortless. There are six Grove connectors onboard, three analog/digital ports, one digital-only port, one i2c port, and one RPI serial port. The labeling on the analog ports (A0, A1, A2) is confusing because they appear to be analog only ports when they can actually be used for either analog devices or devices with a digital interface. Documentation on this is lacking as of this writeup.
Luckily, the 40-pin connector on the GrovePi Zero comes soldered and connected. This is not the case with many other add-on boards. While soldering these connectors is fun for a lot of makers, it gets old fast if you need multiple boards. Once you plug in your individual Grove devices, the overall footprint of your design will grow. Some people will strongly dislike having dangly wires hanging from their Pi Zero. There are some advantages to having our devices off-board. If you want to measure temperature/humidity, on-board HATs suffer from parasitic heat radiating from the Pi itself (example and example). If you want an accurate temperature reading from your Pi, the GrovePi Zero delivers the design you need. You can certainly get creative with device placement if you build your own enclosure.
So far, so good. Let's move on to the process of actually connecting the GrovePi Zero to a Pi Zero.