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February (issue #367) Circuit Cellar

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p.6: Multi-Sensor Device Measures Water Pollution: The UnifiedWater Project, By Andrei Florian

[1] UnifiedWater GitHub repo:
[2] Arduino MKR GSM 1400
[3] 3.7v 1,800mA-hour LiPo battery
[4] GY-21 Temp and Humidity
[5] Water pH Sensor
[6] Water turbidity Sensor
[7] Water temperature Sensor
[8] Neopixel ring
[9] Hologram Sim
[10] Solar panel module
[11] Create a Microsoft account
[12] Create a free Azure account

Adafruit |
Microsoft Azure |

p.18: Giga-Bug: A Retro Game Revamp: Using Raspberry Pi and Python, By Chris Cantrell

[1] GitHub repo for project:
[2] Adafruit Panel (BOM):
[3] Adafruit RGB Bonnet (BOM):
[4] Henner Zeller’s Pi-Display-Driver Repo:
[6] Power Supply (BOM):
[7] SAFFUN generic USB controllers (BOM):
[8] Disassembled Meg-Bug Assembly Code:

Adafruit |
OSH Park |
Parallax |
Raspberry Pi Foundation |
TAP Plastics |

p.24: Smart Gardening System Uses Raspberry Pi: The GardenPi Project, By Richard Sears

Scroll down to the end of this page for an APPENDIX with additional interface screenshots.

Get the Garden Pi schematic on the Circuit Cellar Code and Files Download page.

[1] GardenPr GitHub repo:

Author’s note: Icons used in GardenPi: When you build an interface, how it looks it very important. I would not have been able to have such a nice-looking interface without a lot of cool icons. These icons were mostly free and came from Check them out!

Check them out!

Bosch Sensortec |
Adafruit |
Davis Instruments |
Emoncms |
Flaticon |
Front Panel Express |
Maxim Integrated |
Polycase |
Raspberry Pi Foundation |
SainSmart |
Samsung |

p.38: DDR4 DRAM 101: How it Works, By Nishant Mittal

[1]  JEDEC spec:
[4]  Micron datasheet :

Micron Technology |

p.42: Compact, Reliable Solutions Feed Digital Signage Needs: Small Systems for Big Displays, By Jeff Child

Advantech |
Arbor Technology |
Axiomtek |
Ibase Technology |
Intel |
Nexcom |
OnLogic |

p.49: MCU Software Solutions Evolve for Today’s Needs: Support for AI, IoT and More, By Jeff Child

[1] Microchip’s Ensemble Graphics Toolkit is available at no cost and royalty free for all users and includes full support from Microchip. It is based on the permissive Apache 2.0 open-source license. Training and support are available worldwide at
[2] The I-CUBE-OCTMI is available under commercial license with free usage for evaluation and non-commercial purposes.
[3] Espressif Github
[4] ESP HomeKit SDK integration example:

Espressif Systems |
Infineon Technologies |
Microchip Technology |
NXP Semiconductors |
Octonion |
Renesas Electronics |
ST Microelectronics |

p.54: DATASHEET: Power/Battery Management ICs: Perfecting Power, By Jeff Child

Analog Devices
Dialog Semiconductor
Infineon Technologies
Maxim Integrated
Microchip Technology
NXP Semiconductors
Renesas Electronics
ST Microelectronics
Texas Instruments


Analog Devices

Dialog Semiconductor

Infineon Technologies

Maxim Integrated

Microchip Technology

NXP Semiconductors

Renesas Electronics


Texas Instruments

p.58: EMBEDDED IN THIN SLICES: FreeRTOS (Part 2): FreeRTOS Tasks, By Bob Japenga

[1] “Minds and brains of media multitaskers: Current findings and future directions” Statements like this in their conclusion “in general, heavier media multitaskers often exhibit poorer performance in a number of cognitive domains” make one sit up and take notice.
[2] Reference 1 adds: “many studies report[ing] no performance differences between groups”
[3] October 28th, 2018 article in the Stanford News
[4] This is a very good and helpful tutorial.
[5] Embedded in Thin Slices: Part 1 of the FreeRTOS series in Circuit Cellar December 2020 Issue 365
[6] Check out this email from the creator of Linux Linus Torvalds
[7] Embedded in Thin Slices: Concurrency in Embedded Systems (Part 5)” (Circuit Cellar 271, February 2013)
[8] See  for a great set of documentation for developing safety critical embedded systems

FreeRTOS |

p.62: THE DARKER SIDE: Understanding Proper PCB Design (Part 1): 4-Layer Board Design, By Robert Lacoste

[1]  “Ground Planes: Rules Good, Bad and Ugly”, Circuit Cellar 335, June 2018).

Proteus CAD suite

ViewMate Gerber viewer

KiCad open-source CAD suite

KiCad |
Labcenter Electronics |
Pentalogix |

p.70: FROM THE BENCH: Crafting a Custom Dictionary: Using Liberty BASIC, By Jeff Bachiochi

Noah Webster and George and Charles Merriam –

.dic and .aff files –

“Automating Sudoku” (Circuit Cellar 189, April 2006)

Liberty BASIC |

p.79: The Future of Mesh Networking: Wireless Networks for Tomorrow’s Safety Challenges, By Angela Quinn

Rajant |

Additional interface screenshots for article Smart Gardening System Uses Raspberry Pi: The GardenPi Project, By Richard Sears

Both sources available:

In the next picture, our fish water tank is empty but since the system is set to Automatic, irrigation jobs can still run:

Here we have taken the source selection out of automatic and set it to only use Freshwater:

Here we have set the source to be Fish Water and because there is no fish water available it shuts down the system:

Fish Source is Unavailable

On the main screen, it also gives us a warning that we have no available water and when you enter an irrigation zone, it tells you the same thing:

You will also notice that the “Manual Run” option is also unavailable on the above screen.

Zone Running Information

When a zone is running, the system provides you with visual clues to let you know what is happening and provides you with different options including the ability to “force stop” a zone job. Here we see that a zone is running:

It looks like Zone Four is running right now:

And when we enter zone four, not only do you see we have the option to stop the zone from running but at the bottom of the screen you can see water utilization information including GPM, total gallons this run (at zero since the job just started) and total gallons for all time. You lose your ability to do any schedule or notification changes when the zone is running since it could affect the currently running zone:

Once the zone stops running, the menu goes back to normal:


Water Utilization Information

If you have smart water monitoring installed in your home and are using it, when zones are running you will see water utilization information like you see above, otherwise, it will just show zero. In addition to the individual zones showing this information, the system shows it for all zones:

Go to system tools from the main menu and select the “Water Stats” menu item:



Systemwide notification settings set what types of notifications are available systemwide. Depending on what you would like to use you can choose between E-Mail, SMS text messaging ($$ via Twilio), or Pushbullet.

You can enable or disable them on-demand:

And if notification is disabled at the system level, it also will not be available anywhere else in the system that utilizes notifications, in fact, it won’t even show up as an option. Here SMS is disabled systemwide and it is not available as an option:

Environmental Monitoring

As we previously mentioned, we track a lot of different environmental sensors. To the extent necessary, we can also provide notifications on those readings.

Here is our environmental screen:

Here we can decide what to monitor and what alert setting to use for the notifications:

When you make any changes to the notifications settings, you are given a flash “success” message letting you know that the new settings have been entered into the database.

Power Monitoring

Just like our environmental monitoring, we also monitor power utilization on both our 5V bus and our 120V circuit. We monitor voltage and currently mostly but also provide 5V bus power and DC shunt voltage readout as well thanks to our DC wattmeter installed on the system:

And again, we can set our notifications and alert settings:

RODI Control

The last thing available in Version 1.0.0 of GardenPi is the ability to monitor the capacity and temperature of our RODI water tank. We utilize RODI water as the base water for our fish tank water changes.

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February (issue #367) Circuit Cellar

by Circuit Cellar Staff time to read: 7 min