Introduction

Seeed Studios sent me one of their Grove Starter Kits for the Raspberry Pi Pico to review. The goal of this kit is to make working with microcontrollers accessible for educational purposes. No soldering is required, everything snaps together and away you go. This starter kit comes with a carrier board for the Raspberry Pi Pico (sold separately), a number of connector cables and a selection of devices you can connect up.

What is Grove?

Grove is a standardized connector to allow you to connect devices to a microcontroller using a standard cable using four wires. This is similar to how you can connect devices to your laptop via USB cables. Modern microcontrollers like the various Arduino boards and the Raspberry Pi Pico have pins for multiple communications protocols as well as some general purpose digital and analog connections. The Grove connectors standardize how to wire up a number of these including:

1. UART for standard serial communications
2. I2C for synchronous serial communications
3. Digital includes a wire for power, ground and primary and secondary digital signals
4. Analog includes a wire for power, ground and primary and secondary analog signals

Seeed manufactures carrier boards for several common microcontroller boards. In this case the Raspberry Pi Pico.

The Raspberry Pi Pico fits into the inside pins in the two rows of pin receptors. You can use the outside rows to bypass the Grove connectors and wire the Pico to a breadboard as normal. The Grove ports provide three analog ports, three digital ports, two UARTs and two I2C. There are also breakouts for SPI and debug. Note that the Raspberry Pi Pico I have doesn’t have headers for the debug ports, so doesn’t make use of the debug receptors on this carrier. If you want to avoid soldering altogether, you need to purchase a Pico with pre-soldered headers such as this one.

The carrier board doesn’t have any active components, the PCB routes the pins on the Pico to the correct parts of each Grove connector. 

If you are familiar with the Raspberry Pi Pico, you might know that most of the pins have multiple functions so you can make maximum use of the various pins. The Grove configuration is hardwired for one configuration and if you want to do something different then you need to connect to a breadboard or do some soldering. However, the Grove ecosystem provides lots of devices to connect up here and if you are living in the Grove world then this isn’t a problem.

Sample Program

Seeed’s web page to introduce the Starter Kit has lots of sample projects and I thought as a quick test, I’d wire up the temperature and humidity sensor along with the two line LCD display, I ran into an immediate problem that the sample project on the website was for a different LCD display than included in the kit. However modifying the code for the correct LCD display was fairly easy, mostly looking at one of the other sample projects. I suspect the components might be swapped in and out as supply and demand changes and the web site has trouble keeping up to date.

The direct support for Grove is via MicroPython, with Seeed promising to support Arduino C support sometime soon. You could program this with the RP2040 SDK, since there is direct support for all these devices, but the emphasis here is on educational settings and MicroPython. You need to have the Raspberry Pi Pico connected to a host computer via a micro-USB cable, I used my Windows 10 laptop for this. You write your program in the Thonny Python IDE, which has good support for the Pico, including installing the MicroPython runtime. The Pico version of MicroPython has good low level device support for the RP2040, which means it already knows how to talk to I2C, UARTs, digital and analog devices. Seeed provides MicroPython classes that provide a higher level interface to the various Grove devices included in the starter kit. Below is the source code for reading the temperature and humidity and displaying it on the LCD. The lcd1602.py and dht11.py files are the high level Python classes that Seeed provides for the LCD and digital humidity/temperature sensor.

from lcd1602 import LCD1602
from dht11 import *
from machine import Pin, I2C
from time import sleep

i2c = I2C(1,scl=Pin(7), sda=Pin(6), freq=400000)
d = LCD1602(i2c, 2, 16)
dht2 = DHT(18) #temperature and humidity sensor connect to D18 port

while True:  
    temp,humid = dht2.readTempHumid() #temp:  humid:
    d.home()
    d.print(“Temp:  ” + str(temp)) #display temperature on line 1
    d.setCursor(0, 1)
    d.print(“Humid: ” + str(humid))
    sleep(0.5)

To get this project going, you connect the devices, using the Grove connector cables, enter this small Python program and away you go. Who knew building a microprocessor project and programming it could be so easy?

Summary

Building and programming microprocessor projects can be intimidating, involving soldering small fiddly wires and then writing programs in C and Assembly Language. Seeed simplifies this process by replacing soldering with simple standard connectors and then combines this with simplifying MicroPython high level classes to make the programming simpler. For learning and prototyping DIY projects this is great. This opens the educational potential to younger children, where you might be scared to give them a soldering iron. Further, you are less likely to get parts broken or lost. The Raspberry Pi Pico with its powerful RP2040 CPU runs MicroPython effortlessly and there is plenty of memory for quite large projects.